Search

Gulf War I veterans who were victims of depleted uranium (DU) "friendly-fire" incidents have undergone longitudinal health surveillance since 1994. During the spring of 2019, 36 members of the cohort were evaluated with a monitoring protocol including exposure assessment for total and isotopic uranium concentrations in urine and a comprehensive review of health outcomes, including measures of bone metabolism and bone mineral density (BMD) determination. Elevated urine U concentrations were observed in cohort members with retained depleted uranium (DU) shrapnel fragments. In addition, a measure of bone resorption, N-telopeptide, showed a statistically significant increase in those in the high DU subgroup, a finding consistent with a statistically significant decrease in bone mass also observed in this high DU subgroup compared to the low DU subgroup. After more than 25 y since first exposure to DU, an aging cohort of military veterans continues to show few U-related health effects in known target organs of U toxicity. The new finding of impaired BMD in the high DU subgroup has now been detected in two consecutive surveillance visits. While this is a biologically plausible uranium effect, it is not reflected in other measures of bone metabolism in the full cohort, which have largely been within normal limits. However, ongoing accrual of the U burden from fragment absorption over time and the effect of aging further impairing BMD suggest the need for future surveillance assessments of this cohort.

Laboratory tests vary widely in their utility and each test has unique advantages and disadvantages. For the detection of ethanol use and abuse, a variety of direct and indirect markers are available. Alcohol biomarkers provide objective measures for numerous areas of testing including clinical trials, alcohol abuse, postmortem assessment, and drugs of abuse screening. Because the utility of alcohol biomarkers vary depending on the context in which the results will be used, knowing the analogous distribution of results is of value. Herein we report distributions of ethanol in blood, phosphatidylethanol in blood, ethyl glucuronide in urine, and ethyl sulfate in urine for results reported in the last twelve months by our laboratory. Positivity rates were higher for directed analyses when compared to broad screening or panel tests with the highest overall positivity for ethyl glucuronide and ethyl sulfate. The distribution of results for ethyl glucuronide and ethyl sulfate were higher in clinical testing scenarios compared to forensic and a significant correlation between ethyl glucuronide and ethyl sulfate was found consistent with previous reports. Phosphatidylethanol was rarely ordered for forensic use while distributions between routine clinical and clinical trial use were similar. Approximately 21% of all phosphatidylethanol results were in the moderate to chronic alcohol use category. These results provide a summary of four commonly used direct markers for alcohol use with positivity rates and overall quantitative distributions. These data supply insights broken out by various disciplines where applicable providing a concise comparison of results for these markers.

Purpose: Serum platinum is measurable for years after completion of cisplatin-based chemotherapy (CBC). We report the largest investigation of serum platinum levels to date of 1,010 testicular cancer survivors (TCS) assessed 1–35 years after CBC and evaluate genetic contributions to these levels. Experimental Design: Eligible TCS given 300 or 400 (±15) mg/m2 cisplatin underwent extensive audiometric testing, clinical examination, completed questionnaires, and had crude serum platinum levels measured. Associations between serum platinum and various risk factors and toxicities were assessed after fitting a biexponential model adjusted for follow-up time and cumulative cisplatin dose. A genome-wide association study (GWAS) was performed using the serum platinum residuals of the dose and time-adjusted model. Results: Serum platinum levels exceeded the reference range for approximately 31 years, with a strong inverse relationship with creatinine clearance at follow-up (age-adjusted P = 2.13 × 10−3). We observed a significant, positive association between residual platinum values and luteinizing hormone (age-adjusted P = 6.58 × 10−3). Patients with high residual platinum levels experienced greater Raynaud phenomenon than those with medium or low levels (age-adjusted ORhigh/low = 1.46; P = 0.04), as well as a higher likelihood of developing tinnitus (age-adjusted ORhigh/low = 1.68, P = 0.07). GWAS identified one single-nucleotide polymorphism (SNP) meeting genome-wide significance, rs1377817 (P = 4.6 × 10−8, a SNP intronic to MYH14). Conclusions: This study indicates that residual platinum values are correlated with several cisplatin-related toxicities. One genetic variant is associated with these levels.

TNF antagonists such as infliximab are effective for the treatment of several inflammatory and autoimmune diseases. Recent clinical studies have advocated the importance of measuring trough infliximab levels to guide treatment decisions. We have developed a novel assay for measuring serum free infliximab levels using inductively coupled plasma-mass spectrometry (ICP-MS). The method involves the incubation of patient serum in wells coated with recombinant TNF, followed by detection with lanthanide-labeled monoclonal anti-human IgG1 and ICP-MS analysis. Full method validation was performed and results for clinical samples tested with the new method were compared with those obtained from a capture ELISA and a cell-based assay. Validation of the ICP-MS assay revealed a lower limit of detection of 0.4 μg/mL in serum. The linear range of quantitation was 1-50 μg/mL. The within-run and between-run precision had a coefficient of variation (CV) of10%, and the accuracy of the assay had a CV of15%. In serum samples, the ICP-MS method was devoid of analytical interferences by high levels of hemoglobin, bilirubin and triglycerides. Serum sample results from 123 drug-naïve donors revealed a test cutoff at 0.5 μg/mL. Test results from clinical samples obtained by the ICP-MS method showed strong correlation with both the ELISA and cell-based assay. The ICP-MS methodology presented in this study is a robust method for measuring TNF antagonist serum levels, which makes it well suited for therapeutic drug monitoring in the clinical laboratory.

Toxic adulterants are drug or chemical agents used to add bulk volume to traditional drugs of abuse such as cocaine and heroin. These cutting agents include levamisole, metamizole, noxiptillin, phenacetin and xylazine as well as common legal drugs such as acetaminophen, caffeine, diphenhydramine, lidocaine, quinine, quetiapine and tramadol. Because they possess pharmacological activity they result in exposure of the user, but also in the case of pregnant women, the developing fetus, to potential drug toxicity. We describe the development, validation and implementation of a rapid (48 second sample-to-sample) test based on a qualitative data-dependent liquid chromatography–quadrupole time of flight mass spectrometry method for the analysis of toxic adulterating substances in umbilical cord tissue (UCT) samples. The method provides a means of studying potential in utero exposure to these agents. Library spectra comparison at three different collision energies was used in conjunction with retention time and accurate mass to identify these substances in UCT. Analytically based reporting limits were established to determine positivity rates of adulterants in UCT utilizing a standard addition approach. The method was applied to authentic cocaine and opioid positive UCT to screen for toxic adulterants. There were a total of 82 potential adulterant positives found in a 30-sample cohort of authentic UCT samples, with an average of 2.7 substances per case. Lidocaine was the predominant finding followed by caffeine, and diphenhydramine all of which could result from non-illicit drug exposure, however, there were positives for levamisole, phenacetin, noxiptillin and xylazine none of which are approved in the United States for human therapeutic use. This initial set of data established a preliminary positivity rate of potentially toxic adulterants in UCT samples positive for cocaine or opioid use.

Objectives The objective of this investigation is to explore the utility of using a spot urine sample in lieu of a 24-hour collection in assessing fragment-related metal exposure in war-injured veterans. Methods Twenty-four veterans collected each urine void over a 24-hour period in separate containers. Concentrations of 13 metals were measured in each void and in a pooled 24-hour sample using inductively coupled plasma mass spectrometry. To assess the reliability of spot sample measures over time, intraclass correlations (ICCs) were calculated across all spot samples. Lin’s concordance correlation coefficient was used to assess agreement between a randomly selected spot urine sample and each corresponding 24-hour sample. Results In total, 149 spot urine samples were collected. Ten of the 13 metals measured had ICCs more than 0.4, suggesting “fair to good” reliability. Concordance coefficients were more than 0.4 for all metals, suggesting “moderate” agreement between spot and 24-hour concentrations, and more than 0.6 for seven of the 13 metals, suggesting “good” agreement. Conclusions Our fair to good reliability findings, for most metals investigated, and moderate to good agreement findings for all metals, across the range of concentrations observed here, suggest the utility of spot urine samples to obtain valid estimates of exposure in the longitudinal surveillance of metal-exposed populations.

Arsenic exerts its toxic affects by inhibiting cellular respiration through the targeting of mitochondrial ATP production. The most commonly involved organ symptoms include the central and peripheral nervous systems, cardiovascular system, gastrointestinal system, genitourinary system, hematopoietic system, and the dermatologic system. In the presented case study the details of an acute ingestion are provided giving insight into the immense complexity associated with identifying and treating heavy metal exposures.

Background Immunoassay-based techniques and creatinine quantification have historically been the methods of choice for urine drug screening. Positive presumptive drug screen results are reflexed to more specific, confirmatory testing using gas or liquid chromatography coupled to mass spectrometry. False positives and false negatives with immunoassay techniques are common problems that have substantial down-stream consequences for patient care, laboratory operations, and total costs. Methods The final workflow included rapid enzymatic hydrolysis, rapid liquid chromatographic methods, and time-of-flight mass spectrometry for detection. In total, 84 drugs and metabolites were included and reported qualitatively using 11 isotopically labeled internal standards selected to represent compound classes, retention time, and expected abundances to control for method inefficiencies and matrix suppression/enhancement. The method performance validation included 420 individual urine specimens. Results Of the 420 samples screened by immunoassay, 117 failed to confirm by mass spectrometry and were immunoassay false positives. None of these 117 samples screened positive on the liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) assay. The LC-TOF-MS method failed to detect 1 sample in each of the following classes: buprenorphine, ethanol markers, and opiates owing to concentrations below the established cutoffs. Out of 579 samples, 275 (47.4%) screened positive by LC-TOF-MS for nicotine and at least 2 of its metabolites. Quantitative creatinine comparison to an existing Jaffe method yielded a slope of 0.91 and a correlation coefficient of 0.96. Conclusions We investigated whether immunoassay-based drug screening and creatinine quantification could be sufficiently replaced by a rapid LC-TOF-MS screen with higher specificity and accuracy than existing methods. The LC-LC-TOF-MS method is a sensitive and more specific way to screen for drugs, providing creatinine quantification and potential novel specimen validity testing with the inclusion of nicotine metabolites.

This study aims to establish joint fluid reference levels for Chromium (Cr) and Cobalt (Co) in a reference population of available fluid types. Method performance was evaluated on an existing urine matrix calibration method using inductively coupled plasma-mass spectrometry. Method performance characteristics, including intra- and inter-assay imprecision, accuracy, linearity, AMR (analytical measurement range), sensitivity, and carryover were determined in accordance with clinical laboratory standards. Additionally, analytical and clinical recoveries were assessed to investigate comparability between available joint fluid types and existing calibrators prepared in urine to demonstrate acceptability of a matrix-substitution design. 124 de-identified joint fluid samples submitted for unrelated testing were used to establish the reference levels. Reference levels were determined, by using the 97.5th percentile, to be

Objective: It is recommended that positives in immunoassay drug screens be followed up with more specific confirmatory testing. The drug package insert for pantoprazole mentions reports of false-positive urine screening tests for tetrahydrocannabinol in patients receiving proton pump inhibitors, but no method details or data are given, referenced, or found in literature searches. Thus, we investigated this using our laboratory’s assay. Methods: A spiked sample and samples from 32 patients taking a proton pump inhibitor were analyzed using the EMIT II Plus Cannabinoid assay with a 20?ng/mL cutoff. Additionally, we examined urine samples from 50 patients with false-positive or low-positive screens for evidence of a proton pump inhibitor. To determine whether O-desmethyl pantoprazole sulfate, the major metabolite, shares any structural or electrostatic similarity to suggest a basis for cross-reactivity in the immunoassay, we used computational techniques for analyses. Molecular electrostatic potential energy (MEP) maps were calculated for the global minimum conformers, and the maximum common substructure Tanimoto similarity was calculated for the modeled compounds. Results: Neither the spiked sample nor the patient samples were found to screen positive. None of the false-positive or low-positive screens were found to contain a proton pump inhibitor. Computational studies showed very little similarity in shape or electrostatics between the two molecules. Conclusions: We find no supporting evidence of pantoprazole as the cause of false positives in the EMIT II Plus Cannabinoid assay and caution the use of proton pump inhibitors as an explanation for tetrahydrocannabinol immunoassay false positives.

Background Neuroblastomas are pediatric tumors characterized by overproduction of catecholamines. The catecholamine metabolites, vanillylmandelic acid (VMA) and homovanillic acid (HVA), are used in clinical evaluation of neuroblastoma. Tandem mass spectrometry (LC-MS/MS) is an effective analytical method for measurement of VMA and HVA in urine. Methods Dilute-and-shoot sample preparation was performed in a 96-well format using a liquid handler. Chromatographic separation was achieved using a reverse phase column; detection was accomplished by triple quadrupole mass spectrometry with electrospray ionization in positive mode. Data were acquired by multiple reaction monitoring. Two transitions, quantifier and qualifier, were monitored for each analyte and its stable isotope-labeled internal standard. Analytical specificity studies were performed. Results Injection-to-injection time was 4 min. The method was validated for linearity, limit of quantification, imprecision, accuracy, and interference. Linearity was 0.5–100 mg/l for both analytes. Within-run, between-day, and total imprecision were 1.0–4.1% for VMA and 0.8–3.8% for HVA. The method correlated well with our established HPLC method. Interferences precluding quantitation of VMA in 3% of specimens were reduced significantly (to 0.1% of specimens) using a modified LC gradient to reanalyze affected samples. Conclusions A simple, robust, economical, fast LC-MS/MS method was developed and validated for measurement of urinary VMA and HVA.

Chronic use of opioid medications has been reported to cause altered sexual function. It is not known if non-opioid pain medications have similar effects. Assessment of this effect through the measurement of concentrations of free hormones is limited. Positivity of opioid medications (hydrocodone, oxycodone, morphine, methadone, tramadol and fentanyl) and non-opioid pain medications (gabapentin or pregabalin) in human serum and plasma samples from adult men and women were evaluated for association with concentrations of free testosterone (fTe) and free estradiol (fE2) measured using equilibrium dialysis-liquid chromatography-tandem mass spectrometry methods. Lower concentrations of fTe (p = 0.0253) were observed in samples positive for the hydrocodone, oxycodone and morphine group compared to age matched controls. The presence of methadone, tramadol, fentanyl and pregabalin had no effect on fTe. When compared with age-matched controls, women between 48-55 years of age showed reduced fE2 concentrations in samples positive for tramadol, fentanyl and gabapentin (p = 0.0243, 0.0045 and 0.0050, respectively). Particular opioid medications such as methadone, tramadol or fentanyl and non-opioid medications such as pregabalin or gabapentin may offer advantages over opioid medications for treating pain with fewer endocrinologic side effects. Measurement of free hormones in pain medication users could be important in determining their association with sexual function. Copyright © 2017 John Wiley & Sons, Ltd.

Background Platinating agents are among the most commonly used cytotoxic drugs worldwide. It is recognized that Pt concentration can remain significantly increased in serum up to 20 years after completion of chemotherapy, with levels related to late treatment effects. Methods A Freedom EVO® Tecan liquid handler was used for aliquoting 50 μL serum at 10-fold dilution into 96-well plates. The Teledyne MVX-7100 low-volume autosampler was used for sample introduction into an Agilent 7900 inductively coupled plasma mass spectrometry. There was Results Imprecision was Conclusions This method used an automated liquid handler, a novel 96-well autosampler and 50 μL patient serum to quantify platinum levels. The method was successfully validated according to current clinical guidelines for laboratory developed tests.

Objectives The method described supports the detection of drugs and drug metabolites in the assessment of in utero drug exposure. The presented method employs liquid chromatography–tandem mass spectrometry (LC–MS/MS) as an alternative to a previously validated method using liquid chromatography-time-of-flight mass spectrometry (LC-TOF/MS). A reduction in required chromatographic time and consolidation from two injections to one injection per sample was desired to reduce turnaround time while maintaining the high specificity required. Design and methods Homogenized and extracted umbilical cord samples were analyzed using LC-TOF/MS and LC–MS/MS. The LC–MS/MS chromatographic method used a 3.5 min gradient with an injection-to-injection time of 5 min. Dynamic multiple reaction monitoring was utilized. Results A 55% reduction in total analytical time was achieved by incorporating positive and negative mode acquisition in a single injection with the LC–MS/MS (5 min cycle time) compared to the LC-TOF/MS method that required two total injections (one for positive mode, one for negative mode) and a combined ~ 11.5 min cycle time. 514 patient samples were analyzed by both methods over 20 days. Of the 260 LC-TOF/MS negative samples, 259 were LC–MS/MS negative. Inter-assay imprecision conducted over 20 days using the 50% and 150% QC samples yielded $_amp_$gt; 97% qualitative acceptance and an average percent deviation from the target of 12% and 21%, respectively, using a single point calibration strategy. Conclusions In comparison to the existing LC-TOF/MS method, the LC–MS/MS method delivered the required specificity in a single injection with a 55% reduction in instrument time. Use of a single-point calibration standard and eight representative internal standards provided adequate accuracy for the quantitative assessment of quality control results with qualitative reporting of patient results.

BACKGROUND Serum angiotensin-converting enzyme (ACE) levels may be decreased by use of ACE inhibitor (ACEI) medication. In this study, we determined how often ACE levels were measured in patients receiving ACEI therapy. METHODS ACE levels analyzed over a 54-month preintervention time period at an academic medical center were reviewed retrospectively for tests performed during ACEI therapy. These data were compared with a large, deidentified dataset of ACE levels measured at a national reference laboratory; in vitro studies of ACEI inhibition; and liquid chromatography time-of-flight mass spectrometry detection of lisinopril in a subset of clinical specimens. METHODS Over a 54-month period, 1,292 patients had ACE levels measured, with 108 patients (8.4%) receiving ACEI therapy at the time of testing. ACE levels measured for patients receiving ACEI therapy were substantially lower. In general, clinical teams did not recognize a medication effect on ACE levels. Introduction of a warning prompt in the electronic health record reduced the ordering of ACE levels in patients receiving ACEIs by > 60% in a 17-month postintervention time period. The deidentified dataset of ACE levels at a reference laboratory showed a bimodal distribution, with a peak of very low ACE levels. Using liquid chromatography time-of-flight mass spectrometry, the presence of lisinopril was confirmed in a subset of specimens with low ACE activity. In vitro studies of two different ACE assays showed significant inhibition of activity at clinically relevant concentrations. CONCLUSIONS Assessment of ACE activity is often measured for patients receiving ACEIs, potentially leading to low ACE concentrations and inaccurate interpretations.

A small group of Gulf War I veterans wounded in depleted uranium (DU) friendly-fire incidents have been monitored in a clinical surveillance program since 1993. During the spring of 2017, 42 members of the cohort were evaluated with a protocol which includes exposure monitoring for total and isotopic uranium concentrations in urine and a comprehensive assessment of health outcomes including measures of bone metabolism, and for participants50 years, bone mineral density (BMD) determination. Elevated urine U concentrations were observed in cohort members with retained DU shrapnel fragments. Only the mean serum estradiol concentration, a marker of bone metabolism, was found to be significantly different for lower-vs- higher urine U (uU) cohort sub-groups. For the first time, a significant deficit in BMD was observed in the over age 50, high uU sub-group. After more than 25 years since first exposure to DU, an aging cohort of military veterans continues to exhibit few U-related adverse health effects in known target organs of U toxicity. The new finding of reduced BMD in older cohort members, while biologically plausible, was not suggested by other measures of bone metabolism in the full (all ages) cohort, as these were predominantly within normal limits over time. Only estradiol was recently found to display a difference as a function of uU grouping. As BMD is further impacted by aging and the U-burden from fragment absorption accrues in this cohort, a U effect may be clarified in future surveillance visits.

BACKGROUND: Parathyroid hormone-related protein (PTHrP) is involved in intracellular calcium regulation, neural cell proliferation and synaptic transmission. To date, no studies have been performed to evaluate the potential of PTHrP concentrations in cerebrospinal fluid (CSF) as a biomarker of brain pathophysiology. In this study we evaluated the association between CSF concentrations of PTHrP with the core CSF biomarkers of Alzheimer’s disease (AD). METHODS: PTHrP and calcium were analysed using validated mass spectrometry based methods in a set of CSF samples that tested positive (n = 45) and negative (n = 45) for the AD biomarkers, including total tau protein (T-tau), phosphorylated tau protein (P-tau) and amyloid-β 42 (Aβ42). The measured CSF concentrations of PTHrP and calcium (Ca) were evaluated for association with AD CSF biomarkers. RESULTS: PTHrP and Ca concentrations in CSF samples ranged between 25 and 137 pmol/L and 0.92–1.53 mmol/L, respectively. Higher concentrations of PTHrP were observed in association with increased concentrations of T-tau and P-tau in the AD and the control group; while a stronger correlation was observed in the control group (ρ = 0.6, p

Objectives Chemical analysis of body fluids is commonly requested by physicians. Because most commercial FDA-cleared clinical laboratory assays are not validated by diagnostic manufacturers for “non-serum” and “non-plasma” specimens, laboratories may need to complete additional validation studies to comply with regulatory requirements regarding body fluid testing. The objective of this report is to perform recovery studies to evaluate potential body fluid matrix interferences for commonly requested chemistry analytes. Design and Methods Using an IRB-approved protocol, previously collected clinical body fluid specimens (biliary/hepatic, cerebrospinal, dialysate, drain, pancreatic, pericardial, peritoneal, pleural, synovial, and vitreous) were de-identified and frozen (− 20 °C) until experiments were performed. Recovery studies (spiking with high concentration serum, control, and/or calibrator) were conducted using 10% spiking solution by volume; n = 5 specimens per analyte/body fluid investigated. Specimens were tested on a Roche cobas 8000 system (c502, c702, e602, and ISE modules). Results In all 80 analyte/body fluid combinations investigated (including amylase, total bilirubin, urea nitrogen, carbohydrate antigen 19-9, carcinoembryonic antigen, cholesterol, chloride, creatinine, glucose, potassium, lactate dehydrogenase, lipase, rheumatoid factor, sodium, total protein, triglycerides, and uric acid), the average percent recovery was within predefined acceptable limits (less than ± 10% from the calculated ideal recovery). Conclusions The present study provides evidence against the presence of any systematic matrix interference in the analyte/body fluid combinations investigated on the Roche cobas 8000 system. Such findings support the utility of ongoing body fluid validation initiatives conducted to maintain compliance with regulatory requirements.

Background: Identification of specimens that contain ethylenediaminetetraacetic acid (EDTA) is frequently necessary when investigating potentially mislabeled or improperly collected specimens. Objective: To evaluate the performance of rapid EDTA detection test strips in clinical specimens. Methods: We applied specimens to test strips designed to detect EDTA (QUANTOFIX EDTA) using a pipet ( drop mode ). Reactions were scored visually on a scale from red (no EDTA) to orange (low/indeterminate EDTA) to yellow (contains EDTA). Results: Test strips reliably identified specimens from EDTA-containing tube types. Although test strips did not detect strong reactivity in other specimens, tubes containing NaFl/K-oxalate produced an orange (low/indeterminate EDTA) reaction. Bismuth and citrate levels were higher in specimens after we dipped test strips into solution ( dip mode) . Conclusions: Test strips detected the presence of EDTA in concentrations found in EDTA-containing primary tubes. Test strips were less effective in evaluating low-level EDTA concentrations expected with intravenous line contamination or backflow. Indeterminate reactions required further investigation. Dip mode can produce analytical problems for assays that measure (or are interfered by) the contents of test strips. * EDTA : ethylenediaminetetraacetic acid NaB : sodium tetraphenylborate IRB : institutional review board NaFl : sodium fluoride BD : Becton Dickinson and Co. ACD : acid citrate dextrose ddH2O : demineralized distilled water Bi : bismuth BoCS : bovine calf serum HIL : hemolysis icterus lipemia RBCs : red blood cells PBS : phosphate-buffered saline ICP-MS : inductively coupled plasma-mass spectrometry BAPTA : bis–ethane-N,N,N′,N′-tetraacetic acid PPE : personal protective equipment Y : yellow O : orange R : red PST : plasma separator tube SST : serum separator tube RST : rapid serum tube

We developed and validated a simplified sample preparation for the analysis of antimony (Sb), bismuth (Bi), manganese (Mn), and zinc (Zn) in whole blood. This simplification included a reduction in sample volume, removal of a lengthy acidic digestion, and optimization of the internal standard.Measurement of Sb, Bi, Mn and Zn in whole blood was conducted using inductively coupled-plasma mass spectrometry. Method performance characteristics, including intra- and inter-assay imprecision, accuracy, linearity, AMR, sensitivity, carryover, sample stability and assay stability were determined in accordance with clinical laboratory standards. In addition, analytical and clinical recoveries were assessed to investigate comparability between goat blood matrix and pooled patient blood.Established assay performance characteristics included inter- and intra-assay imprecision4.5% and carryover of0.04% for all four elements, analytical measurement range of 1 to 25 μg/L (Sb and Bi), 1 to 80 μg/L (Mn), and 50 to 1500 μg/dL (Zn), limit of quantification of 1 μg/L (Sb, Bi, Mn) and 50 μg/dL (Zn) (coefficient of variation14%), proportional bias of 0.96 and constant bias of -0.28 (Sb), 0.94 and -0.45 (Bi), 1.07 and -0.37 (Mn) and 0.96 and +18.05 (Zn) based upon repeat patient samples, proficiency testing samples, and comparison to an outside reference laboratory.This method overcomes the laborious acidic heat digestion previously used and replaces it with a simplified sample preparation involving an alkaline dilution. The method requires minimal sample preparation with the dilution of alkaline diluent and is validated to quantify Sb and Bi from 1 to 25 μg/L, Mn from 1 to 80 μg/L, and Zn from 50 to 1500 μg/dL in whole blood.

Heavy metals testing remains an ongoing challenge for diagnosing acute or chronic exposure to heavy metals. In this study, we determined the positivity rates of single element and panel testing for toxic elements, and evaluated the potential utility of an expanded detection protocol for screening of toxic element exposures. The retrospective analysis included data from urine (n = 19,343) and blood (n = 196,019) specimens tested using inductively coupled plasma-mass spectrometry (ICP-MS) for arsenic, cadmium, lead and mercury (blood), and arsenic, cadmium, copper, lead, mercury and zinc (urine). Lead industrial monitoring in blood and cadmium exposure in blood and urine were included to represent directed single element ordering. The percent of positive results, defined as results greater than the upper limit of the reference interval was determined. For blood, the highest positivity was observed for lead occupational exposure monitoring (26.2%) whereas for urine, the highest positivity was observed for zinc testing (28.1%). Remarkably, reanalysis using an expanded panel, of 120 blood and 174 urine specimens originally negative identified 42% (50 of 120) of the blood specimens with at least one elevated result and 48% (83 of 174) of the urine specimens with at least one elevated result. Our results indicate that a broad elemental screening panel may help ensure easier identification of elemental exposure and may eliminate the need for additional follow-up sample collections.

Background Parathyroid Hormone-Related Protein (PTHrP) is involved in intracellular calcium (Ca) regulation, and has been demonstrated to participate in regulation of Ca in brain cells, activation of neurons, and modulation of pain. However, there are conflicting reports regarding the presence of PTHrP in CSF. Design and methods PTHrP and Ca were quantified in paired CSF and serum samples using mass spectrometry-based methods. Associations between PTHrP and Ca concentrations with age, sex and concentrations of nine CSF diagnostic markers in a set of 140 paired serum and CSF patient samples were evaluated. Results The observed median PTHrP concentration in CSF was 51 times higher than in serum; the median concentration of Ca in CSF was 1.8 times lower than in serum. We observed positive correlation between concentrations of PTHrP in CSF and serum (p = 0.013). Distribution of PTHrP concentrations in serum was associated with age (p = 0.0068) and the concentrations were higher in women. In samples with serum calcium concentrations within the reference intervals (n = 118), central 95% distribution of concentrations for Ca-CSF, PTHrP-serum and PTHrP-CSF were 5.4 (4.5–6.1) mg/dL, 1.2 (0.5–2.5) pmol/L, 62 (22–125) pmol/L, respectively. Conclusions Our data demonstrate that PTHrP is a normal constituent of human CSF with median concentrations 51 fold higher than in serum. Elevated serum PTHrP concentrations were positively correlated with age and significantly higher in women. Our data suggest that CSF could be a significant source of circulating PTHrP.

Objectives Liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods that allow accurate quantitation of thyroglobulin (Tg) in the presence of Tg antibodies (TgAbs) have recently become available. Due to cost differences between LC-MS/MS and immunoassay, some laboratories now offer a reflex test strategy that uses LC-MS/MS only for TgAb-positive samples. The goal of this study was to examine utilization of Tg testing strategies and cost savings. Methods Test ordering patterns were examined for over 150,000 orders for TgAb and Tg in our laboratory. The average list price was determined from three separate commercial laboratories offering this testing. Results Data showed that 89% of orders for Tg used the reflex test option, resulting in a savings of over $3 million compared with testing all samples by LC-MS/MS. Of the Tg by LC-MS/MS orders not using the reflex option, 1,663 also included a separate order for TgAb on the same patient sample, representing approximately $170,000 in potentially unnecessary costs from TgAb-negative samples. Conclusions Identifying situations to use more expensive testing methods (eg, LC-MS/MS) only when necessary, such as for TgAb-positive patients, leads to considerable cost savings and a more economical use of valuable health care resources.

Objective. This study investigates the frequency at which quantitative results provide additional clinical benefit compared to qualitative results alone. A comparison between alternative urine drug screens and conventional screens including the assessment of cost-to-payer differences, accuracy of prescription compliance or polypharmacy/substance abuse was also included. Setting and Methods. In a reference laboratory evaluation of urine specimens from across the United States, 213 urine specimens with provided prescription medication information (302 prescriptions) were analyzed by two testing algorithms: 1) conventional immunoassay screen with subsequent reflexive testing of positive results by quantitative mass spectrometry; and 2) a combined immunoassay/qualitative mass-spectrometry screen that substantially reduced the need for subsequent testing. Results. The qualitative screen was superior to immunoassay with reflex to mass spectrometry in confirming compliance per prescription (226/302 vs 205/302), and identifying non-prescription abuse (97 vs 71). Pharmaceutical impurities and inconsistent drug metabolite patterns were detected in only 3.8% of specimens, suggesting that quantitative results have limited benefit. The percentage difference between the conventional testing algorithm and the alternative screen was projected to be 55%, and a 2-year evaluation of test utilization as a measure of test order volume follows an exponential trend for alternative screen test orders over conventional immunoassay screens that require subsequent confirmation testing. Conclusion. Alternative, qualitative urine drug screens provide a less expensive, faster, and more comprehensive evaluation of patient medication compliance and drug abuse. The vast majority of results were interpretable with qualitative results alone indicating a reduced need to automatically reflex to quantitation or provide quantitation for the majority of patients. This strategy highlights a successful approach using an alternative strategy for both the laboratory and physician to align clinical needs while being mindful of costs.

Objectives: Compliance testing in pain management requires a distinct approach compared with classic clinical toxicology testing. Differences in the patient populations and clinical expectations require modifications to established reporting cutoffs, assay performance expectations, and critical review of how best to apply the available testing methods. Although other approaches to testing are emerging, immunoassay screening followed by mass spectrometry confirmation remains the most common testing workflow for pain management compliance and drug abuse testing. Methods: A case-based approach was used to illustrate the complexities inherent to and uniqueness of pain management compliance testing for both clinicians and laboratories. Results: A basic understanding of the inherent strengths and weaknesses of immunoassays and mass spectrometry provides the clinician a better understanding of how best to approach pain management compliance testing. Conclusions: Pain management compliance testing is a textbook example of an emerging field requiring open communication between physician and performing laboratory to fully optimize patient care.

Blood-based biomarkers for traumatic brain injury (TBI) have been investigated and proposed for decades, yet the current clinical assessment of TBI is largely based on clinical symptoms that can vary widely amongst patients, and have significant overlap with unrelated disease states. A careful review of current treatment guidelines for TBI further highlights the potential utility of a blood-based TBI biomarker panel in augmenting clinical decision making. Numerous expert reviews on blood-based TBI biomarkers have been published but a close look at the methods used and the astonishing paucity of validation and quality control data has not been undertaken from the vantage point of the clinical laboratory. Further, the field of blood-based TBI biomarker research has failed to adequately examine sex and gender differences between men and women with respect to the clinical care settings, as well as differences in physiological outcomes of TBI biomarker studies. Discussions of tried-and-true laboratory techniques in addition to a few new ones already operating in the clinical laboratory are summarized with a consideration of their utility in TBI biomarker assessment. In the context of TBI biomarkers, the central concerns discussed in this review are the readiness of the clinical laboratory, the willingness of the research environment and the inherent ability of each to radically affect patient outcomes in TBI.

Objective To facilitate further assessment of transfusion-associated lead exposure by designing a procedure to test packed red blood cells (pRBCs) prepared for transfusion. Study design The relationship between pRBCs and whole blood lead concentration was investigated in 27 samples using a modified clinical assay. Lead concentrations were measured in 100 pRBC units. Results Our sample preparation method demonstrated a correlation between whole blood lead and pRBC lead concentrations ( R 2 = 0.82). In addition, all 100 pRBC units tested had detectable lead levels. The median pRBC lead concentration was 0.8 μg/dL, with an SD of 0.8 μg/dL and a range of 0.2-4.1 μg/dL. In addition, after only a few days of storage, approximately 25% of whole blood lead was found in the supernatant plasma. Conclusion Transfusion of pRBCs is a source of lead exposure. Here we report the quantification of lead concentration in pRBCs. We found a >20-fold range of lead concentrations in the samples tested. Pretransfusion testing of pRBC units according to our proposed approach or donor screening of whole blood lead and selection of below-average units for transfusion to children would diminish an easily overlooked source of pediatric lead exposure.

Methods for circumventing positive drug tests continue to evolve and are often spread through internet websites reporting on the proposed effectiveness of various adulteration methods. Recent claims of the use of zinc added directly to urine or ingested prior to urine collection have prompted investigation into the vulnerability of ELISA-based testing, providing interesting but inconclusive results. We investigated the potential interference of zinc used as a direct adulterant and after zinc self-administration for enzyme multiplied immunoassay technique (EMIT)-based drug abuse testing in urine. Negative urine samples and samples collected before and after zinc self-administration were fortified with d-methamphetamine, benzoylecgonine, morphine and 11-nor-9-carboxy-tetrahydrocannabinol prior to analysis by the EMIT. Our data indicate that zinc added directly to urine in concentrations 5,000 times higher than a typical random urine total zinc concentration is capable of producing false-negative results; however, self-administration of oral zinc was unable to generate random urine total zinc concentrations in the required range. Further, no evidence of a secondary interfering substance was observed as a result of oral zinc self-administration. Our results indicate that the total zinc concentrations required to directly interfere with EMIT-based testing are easily distinguishable from routine random urine total zinc concentrations, and that alleged oral ingestion of zinc does not produce total zinc concentrations capable of direct interference.

As the clinical laboratory attempts to manage and mitigate risk, individual patient results can be a useful complement to routine quality-control materials. Patient results can be used to detect error or identify potential testing complications at all phases of the total testing process. Patient-specific data algorithms include delta checks, tests to verify specimen or tube type, absurdity checks, and result-based reporting. Delta checks are highlighted because they can uniquely point to issues all along the testing cycle, from preanalytical to postanalytical concerns. When used properly, patient results can work to minimize risk and increase the quality of individual patient results.

Metabolized forms of benzodiazepines (benzos) can cause issues with mass spectrometry identification. Benzodiazepines undergo a process called glucuronidation during metabolism that attaches a glucuronic acid for increased solubility. Often in clinical testing an enzymatic hydrolysis step is implemented to increase the sensitivity of benzodiazepines by hydrolyzing β-D-glucuronic acid from benzodiazepine-glucuronide conjugates in urine samples using the β-Glucuronidase enzyme. In this study resorufin β-D-glucuronide, a substrate of the β-Glucuronidase enzyme, was added to patient samples to determine if proper hydrolysis had occurred. The presence of resorufin as an Internal Hydrolysis Indicator (IHI) shows the activity and efficiency of the enzyme in each patient sample. Synthetic/patient urine samples were obtained and mixed with hydrolysis buffer containing resorufin β-D-glucuronide. The β-Glucuronidase enzyme was used to hydrolyze the benzodiazepine analytes as well as resorufin β-D-glucuronide. The enzymatic hydrolysis addition increased the positivity rate of benzodiazepines by 42.5%. The β-Glucuronidase substrate resorufin (IHI) displayed variability in area counts between patient samples. Comparative studies with internal standards and resorufin (IHI) showed no correlation between recovery and analyte variability. Hydrolysis reactions greatly improved the sensitivity of benzodiazepines by liquid chromatography time-of-flight mass spectrometry analysis. The large variation in resorufin (IHI) area counts amongst patient samples indicates possible variability in enzymatic hydrolysis activity. The enzymatic hydrolysis step is a part of the extraction procedure and should be controlled for in each patient sample.

Chronic use of opioid medications has been reported to cause altered sexual function. It is not known if non-opioid pain medications have similar effects. Assessment of this effect through the measurement of concentrations of free hormones is limited. Positivity of opioid medications (hydrocodone, oxycodone, morphine, methadone, tramadol and fentanyl) and non-opioid pain medications (gabapentin or pregabalin) in human serum and plasma samples from adult men and women were evaluated for association with concentrations of free testosterone (fTe) and free estradiol (fE2) measured using equilibrium dialysis-liquid chromatography-tandem mass spectrometry methods. Lower concentrations of fTe (p = 0.0253) were observed in samples positive for the hydrocodone, oxycodone and morphine group compared to age matched controls. The presence of methadone, tramadol, fentanyl and pregabalin had no effect on fTe. When compared with age-matched controls, women between 48-55 years of age showed reduced fE2 concentrations in samples positive for tramadol, fentanyl and gabapentin (p = 0.0243, 0.0045 and 0.0050, respectively). Particular opioid medications such as methadone, tramadol or fentanyl and non-opioid medications such as pregabalin or gabapentin may offer advantages over opioid medications for treating pain with fewer endocrinologic side effects. Measurement of free hormones in pain medication users could be important in determining their association with sexual function. Copyright © 2017 John WileySons, Ltd.

BACKGROUNDThe current gold standard for diagnostic classification of many solid-tissue neoplasms is immunohistochemistry (IHC) performed on formalin-fixed, paraffin-embedded (FFPE) tissue. Although IHC is commonly used, there remain important issues related to preanalytic variability, nonstandard methods, and operator bias that may contribute to clinically significant error. To increase the quantitative accuracy and reliability of FFPE tissue–based diagnosis, we sought to develop a clinical proteomic method to characterize protein expression in pathologic tissue samples rapidly and quantitatively.METHODSWe subclassified FFPE tissue from 136 clinical pituitary adenoma samples according to hormone translation with IHC and then extracted tissue proteins and quantified pituitary hormones with multiplex bead-based immunoassays. Hormone concentrations were normalized and compared across diagnostic groups. We developed a quantitative classification scheme for pituitary adenomas on archived samples and validated it on prospectively collected clinical samples.RESULTSThe most abundant relative hormone concentrations differentiated sensitively and specifically between IHC-classified hormone-expressing adenoma types, correctly predicting IHC-positive diagnoses in 85% of cases overall, with discrepancies found only in cases of clinically nonfunctioning adenomas. Several adenomas with clinically relevant hormone-expressing phenotypes were identified with this assay yet called “null” by IHC, suggesting that multiplex immunoassays may be more sensitive than IHC for detecting clinically meaningful protein expression.CONCLUSIONSMultiplex immunoassays performed on FFPE tissue extracts can provide diagnostically relevant information and may exceed the performance of IHC in classifying some pituitary neoplasms. This technique is simple, largely amenable to automation, and likely applicable to other diagnostic problems in molecular pathology.

The implementation of mass spectrometry to measure serum 25-hydroxyvitamin D [25(OH)D] concentrations has led to concerns regarding the measurement and reporting of the C3-epimer of 25-hydroxyvitamin D(3) [3-epi-25(OH)D(3)], for which there is a near-total lack of data regarding its clinical significance.We developed a chromatographic method to resolve (90%) 3-epi-25(OH)D(3) from 25(OH)D(3) using a pentafluorophenyl propyl chromatographic column. Using LC-MS/MS, we determined the serum concentrations of 25(OH)D(3) and 3-epi-25(OH)D(3) in 626 patients aged 3 days to 94 years undergoing routine vitamin D testing.Comparison between DiaSorin RIA and the new LC-MS/MS method for total 25(OH)D had acceptable agreement. Our data indicate an increase in 25(OH)D(3) rather than a reduction in epimer concentration. An average of 3.3 ng/ml of 3-epi-25(OH)D(3) was detected in adolescents and adults. Inclusion of 3-epi-25(OH)D(3) in the total 25(OH)D(3) concentration resulted in 9% (1 year) and 3% (1 to 94 years) potential misclassification of patients as vitamin D sufficient.The new LC-MS/MS method is capable of chromatographically separating 25(OH)D(3) and 3-epi-25(OH)D(3). It was used to confirm that the contribution of 3-epi-25OHD(3) to total 25OHD(3) concentrations decreases with age in infants and is detectable in adults.

Background Despite their widespread use, the performance of delta check rules is rarely evaluated because errors are rare and lack a gold standard for detection. In this study we used a simulation-based approach to compare strategies for empirically defining criteria for univariate delta checks, and assessed the performance of these rules for detecting mislabeled specimens in 2 inpatient populations. Methods We performed simulations using historical laboratory test results by randomly sampling pairs of specimens successively drawn from the same patient or two different patients. We evaluated the performance of delta check rules using a variety of thresholds, including those currently in use in our laboratory. Result Mean corpuscular volume had the highest positive predictive value for specimen mislabeling, and produced the fewest false positives. Conversely, rules using other laboratory tests had considerably poorer performance. Several of the “best guess” thresholds historically used in our laboratory, notably those for potassium and anion gap, were predicted to have extremely low yields. In addition, rule performance was not consistent between the two patient populations. Conclusions The low yield of delta checks based on any single analyte should prompt careful evaluation of their practical utility. Furthermore, our results indicate that it may not be possible to generalize delta rules across institutions.

Mass spectrometry is an analytic technique with high specificity and a growing presence in laboratory medicine. Various types of mass spectrometers are being used in an increasing number of clinical laboratories around the world, and, as a result, significant improvements in assay performance are occurring rapidly in areas such as toxicology, endocrinology, and biochemical genetics. This review serves as a basic introduction to mass spectrometry, its uses, and associated challenges in the clinical laboratory and ends with a brief discussion of newer methods with the greatest potential for clinical diagnostics.

BACKGROUND 1α,25-dihydroxy vitamin D [1,25(OH)2D] is the active metabolite of vitamin D. Antibody-based detection methods lack specificity, but when combined with isotope dilution/ultra-performance liquid chromatography (UPLC)–tandem mass spectrometry, immunoextraction provides an attractive method for 1,25(OH)2D. We developed a method for simultaneous quantification of 1,25(OH)2D2 and 1,25(OH)2D3 with a 4.6-min instrument cycle time. Results are available 36 h after sample preparation begins. METHODS Sample preparation consisted of protein precipitation, immunoextraction with solid-phase anti-1,25(OH)2D antibody, and derivatization with 4-phenyl-1,2,4-triazoline-3,5-dione. Analytes were resolved using reversed-phase UPLC and quantified using positive ion electrospray ionization–tandem mass spectrometry. We used hexadeuterated 1,25(OH)2D3 and 1,25(OH)2D2 as internal standards and performed method comparisons against the DiaSorin RIA and an LC-MS/MS method available at a reference laboratory. RESULTS 1,25(OH)2D3 intraassay and interassay imprecision was 5.6% and 8.0% (120 pmol/L) and 8.7% and 13% (48 pmol/L). Limits of detection and quantification were 1.5 pmol/L and 3.0 pmol/L, respectively. 1,25(OH)2D2 intraassay and interassay imprecision was 8.7% and 11% (186 pmol/L) and 11% and 13% (58 pmol/L). Limits of detection and quantification were both 1.5 pmol/L. Comparison with RIA had a proportional bias of 0.75, constant bias of −4.1, and Pearson correlation (r2) of 0.31. Comparison with a reference LC-MS/MS assay had a proportional bias of 0.89, constant bias of 3.7, and r2 of 0.88. CONCLUSIONS Protein precipitation with antibody-based extraction is effective for sample preparation before LC-MS/MS analysis of derivatized 1,25(OH)2D. This method appears to have improved specificity over a clinically used RIA with low imprecision and limits of detection.

We developed and validated the use of synthetic urine as a matrix substitute for standard and quality control material preparation in the clinical assessment of iodine status in urine.Measurement of iodine in urine was conducted using inductively coupled-plasma mass spectrometry. Analytical and clinical recoveries were assessed to investigate comparability between synthetic urine and pooled patient urine. Method performance characteristics were determined in accordance with clinical laboratory standards.Established assay performance characteristics included inter- and intra-assay imprecision10%, carryover of0.2%, analytical measurement range of 5 to 1000μg/L, limit of quantification of 5μg/L (coefficient of variation10%), proportional bias of 0.92 and constant bias of 8.8 in comparison to an outside reference laboratory.Synthetic urine is an appropriate alternative matrix for standard and quality control material preparation for the measurement of iodine in urine.

We have developed and validated a method for the simultaneous quantitative measurement of total uranium (TU) and uranium 235 U/238 U isotopic ratio (UIR) in urine by inductively coupled plasma mass spectrometry (ICP-MS) using a Thermo Scientific iCAP-Q instrument. The performance characteristics of the assay were determined to be in compliance with clinical laboratory standards. The assay was linear in the concentration range of 1.0 to 500.0 ng/liter TU. The method was precise and accurate with limits of detection of 2.5 ng/liter for TU and 9.8 ng/liter for UIR. The accuracy was >93% and the coefficient of variation (% CV) was

We developed and validated a method for the assessment of thirteen separate trace and toxic elements using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Included elements were as follows: aluminum, chromium, manganese, iron, cobalt, nickel, copper, zinc, arsenic, molybdenum, cadmium, tungsten, and lead. The measurements of all elements in urine samples were conducted using ICAP-Q ICP-MS in a single method. The performance characteristics of the assay were determined according to clinical laboratory standards. The assay was linear in the concentration range of 1.0 to 1000.0 µg/liter for all elements. The method was precise and accurate with limits of quantitation of 1 µg/liter for chromium, manganese, cobalt, nickel, copper, cadmium, tungsten, and lead; 2 µg/liter for iron and arsenic; 5 µg/liter for aluminum; and 50 µg/liter for zinc. This method has successfully been used for the assessment of all thirteen elements included in urine and has been shown to be effective as a simple, precise, and sensitive analytical technique for biological monitoring of urine samples. © 2018 by John Wiley & Sons, Inc.

INTRODUCTIONParathyroid hormone–related peptide (PTHrP) is involved in activating pathways, allowing tumor cells to form bone metastases. Measurement of PTHrP is used for the diagnosis and clinical management of patients suspected of hypercalcemia of malignancy. We developed an LC-MS/MS method for measuring PTHrP, established sex-specific reference intervals, and assessed the method's performance.METHODSPTHrP was enriched from plasma samples with rabbit polyclonal anti-PTHrP antibody conjugated to magnetic beads. Enriched PTHrP was digested with trypsin, and PTHrP-specific tryptic peptide was analyzed with 2-dimensional LC-MS/MS in multiple reaction monitoring mode.RESULTSThe lower limit of quantification was 0.6 pmol/L, and the upper limit of linearity was 600 pmol/L. Total imprecision was CONCLUSIONSPTHrP is a normal constituent in circulating blood and its concentrations are substantially underestimated by commercial RIAs, causing false-negative results in samples from patients suspected of hypercalcemia. Our observations suggest a link between increased concentrations of PTHrP in postmenopausal women with low body mass index and increased incidence of osteoporosis.

Meconium drug testing is performed to detect potentially harmful drug exposures in a newborn. Interpretation of meconium drug testing results can be complicated based on the patterns and proportional concentrations of the drug(s) and/or drug metabolite(s) detected.The objective of this study was to analyze meconium drug testing patterns in a de-identified dataset from a national reference laboratory (n = 76,631) and in a subset of the data, wherein specimens originated at a single academic medical center for which detailed chart review was possible (n = 3635). Meconium testing was performed using 11 immunoassay-based drug screens. Specimens that were positive for one or more drug screens were reflexed to corresponding confirmation tests performed by gas chromatography or liquid chromatography with mass spectrometric detection, targeted to identify and quantitate specific parent drug(s) and metabolite(s).The positivity rate was the highest for the cannabis metabolite 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (25.2%, n = 18,643), followed by opiates/oxycodone (23.2%, n = 17,778), amphetamine/methamphetamine (6.7%, n = 5134), cocaine metabolites (5.5%, n = 4205), methadone (5.3%, n = 4093), benzodiazepines (3.4%, n = 2603), barbiturates (1.1%, n = 834), propoxyphene (1.0%, n = 749), and phencyclidine (0.1%, n = 44). Based on documented pharmacy history, drugs administered to either the mother or newborn during the birth hospitalization were detected in meconium, providing evidence that drugs can be incorporated into meconium rapidly. Drugs administered directly to the newborn after birth were recovered in meconium as both parent drug and metabolites, providing evidence of neonatal metabolism. Overall, patterns observed in meconium exhibited many similarities to those patterns commonly reported with urine drug testing.Interpretation of meconium drug testing results requires comparison of results with clinical and analytical expectations, including maternal admissions to drug use, pharmacy history, recognized metabolic patterns for drugs of interest, cutoff concentrations, and other performance characteristics of the test. Concentrations of drug(s) and drug metabolites(s) may not reliably predict timing of drug use, extent of drug use, or frequency of drug exposures.

BACKGROUND: Rapid test strips for ethylenediaminetetraacetic acid (EDTA) can be used to verify correct specimen types for clinical assays which require, or cannot be performed on, plasma collection tubes containing EDTA anticoagulant. As the test strip reaction chemistry is based on a color change induced by chelation of bismuth from a xylenol orange complex, we hypothesized that any agent capable of chelating bismuth might induce false positive test strip reactivity. The present study was therefore designed to evaluate the potential for test strip interference by chelating agents commonly used in the treatment of trace and heavy metal toxicity. METHODS: A digital color detector mounted on a 3D-printed test strip holder was used to quantitatively assess test strip reactivity and evaluate concentration-response relationships of eight commercially available chelating agents. RESULTS: This approach revealed the following rank-order potency: K2EDTA = Na2EDTA > ethylene glycol tetra-acetic acid (EGTA) > dimercaptosuccinic acid (DMSA) > 2,3-dimercapto-1-propanesulfonic acid (DMPS) > penicillamine (PEN). Both deferoxamine (DEF) and alpha lipoic acid (ALA) were non-reactive at 10 mM concentrations. CONCLUSIONS: These experiments demonstrate that multiple substances can induce EDTA rapid test strip reactivity, but only at concentrations higher than might be expected during therapeutic chelation therapy. These agents are therefore unlikely to cause false positive results in routine clinical laboratory specimens.