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Background Daratumumab (DARA) is a fully human anti-CD38 IgG1-κ monoclonal antibody drug used in the treatment of multiple myeloma (MM). While serum protein electrophoresis (SPEP) is an important assay for diagnosis and monitoring of patients with MM, DARA can appear in the γ-region as a single band and interfere with the interpretation of SPEP results. An approach to detect the interference is measuring the quantity of DARA in serum samples and assessing its impact on SPEP results. Immunoassays based on label-free technologies, i.e. label-free immunoassays (LFIA’s), can achieve real-time immunometric measurement without attaching a reporter molecule (enzyme, fluorophore, etc.) to the immunocomplex. The recorded time course of the immunocomplex formation allows for quantitation on initial binding rate, which facilitates rapid measurement within a few minutes. Based on the thin-film interferometry (TFI) technology, a rapid LFIA was established for the quantitation of DARA in serum samples. Methods The TFI-based LFIA for DARA was validated for imprecision (CV), accuracy, limit of quantitation (LOQ), and analytical measurement range (AMR). Interference to the LFIA was evaluated using a group of protein samples, as well as hemolytic, lipemic, and icteric clinical samples. Results The precision of the TFI-based LFIA’s for DARA ranged from 6.5% to 10.7% (within-run CV), and 7.4% to 11.6% (between-run CV), with a bias of −2.1% to 10.1%. The LOQ was 10 μg/ml (n = 4, CV 9.8%), with an AMR ranging from the LOQ to 1000 μg/ml. The LFIA was used to measure 37 patient samples submitted for SPEP testing. The LFIA results were 100% consistent with the history of DARA use as documented in the medical record. Conclusions The TFI-based LFIA was successful at accurately identifying DARA in serum samples and can be used to identify DARA interference in SPEP testing. This work demonstrates the applicability of label-free technologies, particularly the TFI technology, to clinical diagnostic needs. Given the simplicity and the speed of the testing process, the TFI technology provides a unique testing approach for the measurement of proteins in clinical samples.

Background Sulfonylureas are antidiabetic agents widely prescribed for the treatment of type-II diabetes. Detection of the presence of sulfonylureas in cases of unexplained hypoglycemia rules out other underlying pathophysiological conditions. The goal of this study was to develop and validate a qualitative liquid chromatography tandem mass spectrometry (LC–MS/MS) assay for the rapid identification of sulfonylureas in serum. Methods An LC–MS/MS assay was developed using an Agilent HPLC with an AB Sciex 3200 LC–MS/MS operating in ESI positive mode. Linearity, LOD, precision, matrix effect, recovery, carry-over and stability of the final method were evaluated for method validation. Concordance with another clinically validated LC–MS/MS method was evaluated using remnant samples from patients prescribed a sulfonylurea. Results The assay performed well with all validation data meeting pre-determined criteria. The method comparison study showed a correlation coefficient of 0.99 for glipizide, the most common sulfonylurea, despite both methods being validated as qualitative methods. To date the validated assay has been utilized in 19 cases of unexplained hypoglycemia presenting to the emergency department, in which 5 were sulfonylurea positive. Conclusion We have developed a rapid and sensitive LC–MS/MS sulfonylurea assay, and utilized this assay to assist in the differential diagnosis of unexplained hypoglycemia.

Background Macro-aspartate aminotransferase (macroAST) is a high molecular weight form of AST that is usually formed through association with immunoglobulin (Ig) in the circulation. As a result of reduced inactivation, clearance or excretion, AST values are persistently increased. This can lead to problems interpreting these values and diagnosing the patient, especially if clinicians are not aware of this phenomenon. Methods For a case of suspected macroAST, we compared three simple methods: polyethylene glycol precipitation, ultrafiltration, and Ig depletion using protein A and G. Results All three methods were consistent with a diagnosis of macroAST. Conclusions The protein A and G method was straightforward and provided unambiguous results. However, given the affinity of protein A and protein G, it likely only detects AST-IgG macrocomplexes.

Background The analysis of blood for β-sitosterol and campesterol is the measures of cholesterol absorption while lathosterol is a measure of cholesterol synthesis. Methods The biological variability of β-sitosterol, campesterol, and lathosterol was measured using liquid-chromatography tandem mass spectrometry from a cohort of 25 apparently healthy subjects, where blood was taken once every weeks for 6 weeks. The analytical, intra-individual, and group inter-individual variations (CV A , CV I , and CV G , respectively) were calculated. Results Using absolute values, the CV I for β-sitosterol, campesterol, and lathosterol was 11.8%, 11.8%, and 22.5%, respectively, and the CV G was 28.5%, 28.8%, and 52.0%, respectively. This produced reference change values of about 24–36% for declining values and 32–47% for increasing values. The index of individuality was between 0.41 and 0.58, indicating that population based reference values are of little use for these biomarkers. The number of points needed for a homeostatic setpoint was 5 samples for β-sitosterol and campesterol, and 19 samples for lathosterol. Similar findings were observed for values when normalized to total cholesterol. These results were higher than the biological variation for total, low density and high density cholesterol obtained from the literature. Results were essentially identical when sterol values were corrected to their respective total cholesterol concentration. Conclusions The establishment of the biological variation for these biomarkers enables their use in the interpretation of results from clinical trials and lipid lowering treatment of patients at risk for cardiovascular disease in clinical practice.

Whilst it is formally stated that cardiac troponin is only released when cardiac myocytes undergo necrosis, there are a number of clinical situations where troponin is present in the circulation, without any apparent cardiac injury. In these cases, troponin half-life in the circulation is usually substantially shorter than that seen when troponin is released following myocardial infarction with frank necrosis. A mechanism has been described in liver, where large cytoplasmic molecules can pass from the intra- to extra-cellular space without cellular necrosis occurring. This occurs by the formation of membranous blebs which bud off from the plasma membrane of the cell. Blebs develop during cellular ischemia. If the ischemia is limited and re-oxygenation occurs, the blebs may be released into the circulation without rupture of the plasma membrane, resulting in a one-off release of cytoplasmic contents including macromolecules. Evidence from cardiac studies is presented supporting the presence of membranous blebs in cardiac myocytes, enabling troponin to be released from cardiac cells due to ischemia alone, without necrosis. Refereed/Peer-reviewed

The development of highly sensitive cardiac troponin (cTnI) assays has increased the number of true and false positive results for patients suspected of acute myocardial infarction (AMI). Cases are reported whereby the use of serial testing, the 99th percentile cutoff, and the application of biological variation of cTnI were used to help determine ischemic vs. non-ischemic causes of myocardial injury.cTnI was measured using the Siemens Ultra assay from 13 representative patients who presented to the emergency department with symptoms suggestive of acute cardiac disease. Based on a previous study, reference change values of a 46% increase and 32% decrease were used to interpret results. These differences were compared against the patient's discharge diagnosis.Two patients who subsequently ruled in for AMI had a negative cTnI (0.04 microg/l) and borderline positive cTnI (0.07 microg/l) at admission, respectively. While the 4-6 h results were also borderline, there was a significant increase from the baseline (+575% and +50%, respectively) to suggest the presence of an acute cardiac event. Two other AMI cases document the significant cTnI decline in results after peak values. In 7 other non-AMI cases (heart and renal failure, gastrointestinal bleeding, stroke and venous thrombosis), while baseline concentrations were clearly positive (0.18-2.12 microg/l), subsequent serial samples were not significantly increased or decreased from baseline. These findings were not typical for AMI. There were 2 cases with acute blunt cardiac trauma and intracranial hemorrhage, respectively, that produced cTnI results that were initially low (0.04 and 0.05 microg/l, respectively), but significantly increased with serial testing thereby producing false positive Delta cTnI results for AMI.Serial testing for troponin was useful in differentiating early AMI from non-ischemic causes of troponin increases. However, non-AMI patients with acute cardiac injury can produce troponin results that mimic AMI. Therefore serial troponin testing must be used in conjunction with clinical presentation and other laboratory findings.

NT-proBNP measurements aid in the evaluation of patients with suspected heart failure (HF) and may facilitate risk stratification in patients with HF and acute coronary syndrome (ACS). Point-of-care (POC) assays may provide more timely results and potentially improve patient outcomes.We evaluated the analytical performance of the Response Biomedical Corporation whole blood RAMP amino-terminal pro-B type natriuretic peptide (NT-proBNP) POC assay compared to the Roche Elecsys proBNP (NT-proBNP) assay.Intra-day and total imprecision (% CV) ranged from 5.5% to 10.3% at 140, 449 and 1675 ng/L. The lowest concentration that yields a 20% CV was 57 ng/L. The lower limit of detection was 18 ng/L. The upper limit of linearity was validated to 23,428 ng/L with an average recovery of 95%. Correlation by Passing and Bablok regression yielded RAMP=1.01 Elecsys+14.6, r=0.98 (n=540; range of Elecsys values5 to35,000). Concordance of RAMP versus Elecsys using cut-offs of 125 ng/L for subjects75 years and 450 ng/L for subjectsor =75 was 92% (95% CI 89-94%) for a group consisting of 127 apparently healthy individuals and 208 non-healthy subjects without HF, and 99% (95% CI 97-100%) for patients with HF, using the New York Heart Association (NYHA) functional classification. Overall, 80%, 87%, 97% and 100% of the RAMP results and 77%, 85%, 96% and 100% of the Elecsys results were greater than the age appropriate cut-off for NYHA I, II, III or IV groups. For both the RAMP and Elecsys results, the median NT-proBNP value was statistically correlated (increasing) with NYHA I, II, III or IV groups, respectively (p0.0001), with no significant difference between the two methods.The POC Response Biomedical RAMP NT-proBNP assay provides comparable results that measured on the FDA cleared Roche Elecsys central laboratory platform.

Background The first immunoassay was described by Berson and Yalow in 1959. Their work resulted in their receipt of the Nobel Prize in Medicine in 1977. Since this introduction, immunoassays have evolved considerably. Methods There have been several milestones that have led to the proliferation of modern immunoassays. The development of monoclonal antibodies from mouse hydridoma cells by Millstein and Kohler (Nobel Prize in 1984) enabled the production of high quantities of antibodies with well characterized epitope specificity. The first homogenous immunoassay (no separation step required) was the Enzyme Multiplied Immunoassay Technique (EMIT), which enabled adaptation of this assay onto automated chemistry platforms. EMIT was also one of the first immunoassay that made use of non-isotopic labels. Other non-isotopic labels became available such as chemiluminescence to improve the analytical sensitivity of immunoassays. The advantages of high-sensitivity immunoassays have created expanded diagnostic roles for some existing assays such as thyroid stimulating hormone for hyperthyroidism, C-reactive protein for cardiovascular risk assessment, and other applications. The development of instrumentation capable of automated heterogeneous immunoassays (separation step to improve sensitivity) has enabled movement of this technology from the “special chemistry” sections of a clinical laboratory into the "core" laboratory with other high-volume testing. Conclusion Today, immunoassays play a prominent role in the analysis of many clinical laboratory analytes such as proteins, hormones, drugs, and nucleic acids. The future involves development of assays with higher sensitivities which will enable the discovery of new biomarkers for disease diagnosis, and technology that will enable simultaneous multimarker analysis of tests whose needs are naturally grouped together (e.g., cytokines and allergens).

Background Intravenous epinephrine (EPI) is used as a pharmacologic agent to acutely treat patients in cardiac arrest. Unfortunately, there have been several homicide cases where hospitalized patients died due to a purposeful overdose of epinephrine. We measured plasma epinephrine metabolites (metanephrine, MET, and normetanephrine, NMET) to determine if exogenous epinephrine can be distinguished from endogenous epinephrine concentrations in a controlled animal study. Methods Rabbits were subjected to three different protocols. In the physiologic stress group ( n =8), rabbits were immobilized for 30 min in a restraining tube. In the sub-lethal dose ( n =9), 0.01 mg/kg of epinephrine was injected into anesthetized rabbits. In the lethal dose group ( n =8), 1.0 mg/kg of epinephrine was administered into anesthetized rabbits. Blood was collected at regular intervals for up to 480 min. The plasma metanephrine and normetanephrine concentrations were measured by liquid chromatography/mass spectrometry and the serum cortisol concentrations by immunoassay. Results Serum cortisol and plasma metanephrine and normetanephrine concentrations increased in the stressed animals during immobilization demonstrating the endogenous stress model. Following a sub-therapeutic epinephrine dose, plasma metanephrine increased while plasma normetanephrine decreased. The peak plasma metanephrine concentrations were similar to the concentrations observed in the stressed animals; however, the ratio of plasma metanephrine to normetanephrine was significantly different. In the lethal epinephrine dose, both the plasma metanephrine concentrations and ratio of metabolites were significantly greater than those observed in the endogenously stressed animals. Conclusions The ratio of plasma metanephrine to normetanephrine is the best marker to determine the presence of exogenous therapeutic and lethal epinephrine administration. However, there were limitations to the study design that could alter these conclusions.

Background Some patients show warfarin resistance needing more than 70 mg of warfarin per week. In this study, we examined if C3435T polymorphism of MDR1 gene could be a factor of warfarin resistance. Methods We examined 196 blood specimens from the patients who took warfarin more than 42 mg/week for at least 1 year. The subjects consisted of 74 European Americans, 59 African Americans, 42 Hispanic Americans and 21 Asian Americans. Genotype of C3435T polymorphism was determined by using real-time polymerase chain reaction (PCR). Results Ninety (45.9%) of the 196 patients had C3435T genotype and the remaining patients had C3435C genotype (35.7%) and T3435T genotype (18.4%). Mean dose of warfarin of patients with C3435C, C3435T and T3435T genotypes were 59.5 mg/week, 56.9 mg/week and 55.6 mg/week, respectively. There was no statistical difference in the dose of warfarin between the 3 genotypes within each race. Conclusion Our results suggest that C3435T polymorphism of MDR1 gene is not associated with warfarin resistance.

Background: B-type natriuretic peptide (BNP) is a cardiac hormone that regulates hemodynamic equilibrium. In the circulation, its activity is controlled by proteolytic factors. Accurate measurement of BNP in a patient's plasma may be affected by degradation due to proteolysis. Objective: We report on the identification and performance of classes of protease inhibitors that stabilize BNP in plasma. Design and methods: Using the Bayer ADVIA Centaur® BNP assay, we measured the effect of arginine, serine and/or specific kallikrein protease inhibitors (PIs) on exogenous spiked or endogenous BNP in patient plasma. Results: Compared to controls without inhibitor, all PIs were capable, to varying degrees, of retarding the rate of proteolytic degradation. The kallikrein-specific inhibitor, d -Phe–Phe–Arg–chloromethylketone (PPACK II) was most effective as a single constituent and was able to eliminate BNP degradation in patient samples for up to 6–10 days when stored at 2–8 °C. Conclusions: The stability of BNP was markedly increased in the presence of kallikrein-specific PPACK II and a broad spectrum of serine PIs. Use of these compounds offers a simple method of extending sample handling and storage of plasma samples containing BNP.

Background : Brain natriuretic peptides (BNPs) are useful in the assessment of heart failure, left ventricular dysfunction, and acute coronary syndromes. Methods : We performed a multicenter evaluation of the automated Roche NT-proBNP assay and compared its performance to the Biosite Triage BNP assay. Results : The N-terminal (1–76) pro brain natriuretic peptide (NT-proBNP) method is precise (CV≤6.1%), has a wide dynamic measuring range (30–35,000 ng/l), is free from common interferences, and does not cross-react with BNP. EDTA or heparinized plasma samples collected in glass or plastic tubes can be used, and samples are stable at room temperature or 4 °C for up to 3 days. In contrast, the Biosite BNP assay has >2-fold higher CV, and plasma samples are more labile when stored at room temperature and 4 °C. Comparison studies showed a reasonable correlation between NT-proBNP and BNP assays, with a substantially higher slope bias of 6–20 for the NT-proBNP assay. Conclusions : The automated Roche NT-proBNP assay has good analytical performance and better precision than the Biosite BNP assay. Unlike BNP, NT-proBNP is stable in EDTA plasma for 3 days at room temperature or longer at 4 °C. The Roche NT-proBNP is fully automated and will accommodate the testing of large numbers of clinical samples for assessing cardiac dysfunction.

Signify® ER Drug Screen Test (Signify ER) and Triage® Drug of Abuse Panel plus TCA (Triage DOA Panel) rapid drug screening devices were compared at four laboratories. Both assay systems are point of care immunoassays, measuring phencyclidine, barbiturates, amphetamine, cocaine metabolite, methamphetamine, tricyclic antidepressants, opiates, marijuana metabolite, and benzodiazepines in human urine. The performance of these two assay systems, including a cutoff verification and cross-reactivity using spiked urine specimens and accuracy using clinical urine samples, was investigated. The cutoff verification study showed that the Signify ER had 95.4% precision for all drugs tested at concentrations of 50%, 75%, 125%, 150%, and 200% of cutoffs compared to 90% precision obtained with Triage DOA Panel. Accuracy studies testing 53 negative urine samples demonstrated that both Signify ER and Triage DOA Panel have 100% specificity. Testing of 693 positive urine samples demonstrated that Signify ER and Triage DOA Panel have sensitivities of 99.8% and 99.3%, respectively, with an accuracy of 99.9% and 99.6%. A total of 527 compounds were tested for the cross-reactivity study. Eighty-seven structurally related drugs and metabolites were found to cross-react with at least one of the nine tests of the Signify ER. Four hundred forty structurally unrelated compounds that can be found in human urine were shown not to cross-react with the Signify ER. In terms of operating characteristics, the Signify ER device is simpler since only a single pipetting step is required, and reaction completed within 8 min.

Background Molecular profiling assays have emerged as a promising tool in tumor diagnosis. Recent advances have allowed the use of formalin-fixed, paraffin-embedded (FFPE) tissues in such assays involving the use of microarrays. The Pathwork Tissue of Origin (TOO) Test was developed for use with FFPE tissue to aid tumor diagnosis. We sought to determine the performance of the TOO test on routine specimens from an independent laboratory. Methods Forty-five blinded, archived clinical specimens from the UCSF Department of Pathology were tested. Total RNA was processed to prepare labeled cDNA for hybridization to Pathchip microarrays. Hybridization data was analyzed with a 2000-gene classification model to quantify similarity between RNA expression of the study specimens and the 15 tissues on the test panel. Results 44/45 (98%) specimens were successfully processed. 37 cases met study inclusion criteria. Of these, 35 (95%) gave results which were in agreement with the reference diagnosis. In no case was the reference diagnosis ruled out. Conclusions The Tissue of Origin Test gave a high agreement with the reference diagnosis when archived clinical specimens from UCSF were assessed. Molecular profiling assays are highly accurate, and can be a useful tool in cancer diagnosis.

As part of a symposium on laboratory medicine, a colloquium on point-of-care testing was held in June 1999 where four experts were invited to produce recommendations and opinions on the use of point-of-care testing under various clinical venues. Each commented on costs for providing POCT services. A total of eleven recommendations and four opinions were rendered and discussed in an open forum. While one expert concluded that some forms of POCT are less expensive than central laboratory testing if entire laboratory workstations are eliminated, another expert suggested that POCT offered little advantage if rapid transport systems are available. A recommendation was made that POCT be considered for analytes that have a required reporting turnaround time of

The purpose of this study is to describe sex and geographic differences in apolipoproteins (apo) A-I and B and lipoprotein(a) [Lp(a)] concentrations in elderly Europeans. Subjects were 2164 elderly participants of the SENECA study from different regions of Europe. Sera for apo A-I, apo B, and Lp(a) measurement were available for 1703 individuals. In men, mean values ranged from 1.38 to 1.79 g/l for apo A-I, 1.03-1.36 g/l for apo B, and 0.26-0.67 g/l for Lp(a). In women, mean values ranged from 1.54 to 1.98, 1.20-1.51, and 0.26-0.68 g/l for apo A-I, apo B, and Lp(a), respectively. A comparison of northern (Norway, Denmark, Netherlands), middle (France, Switzerland), and southern (Portugal, Spain, Italy, Greece) communities showed a less atherogenic profile in the south, including lower LDL cholesterol, apo B, TC/HDL cholesterol ratio, and apoB/apo A-I ratio. Men, but not women, also had significantly higher HDL cholesterol and apo A-I concentrations in the South. Paradoxically, Lp(a) concentrations were generally high among all elderly and were significantly higher in the southern communities. These data show that the elderly in Europe are very heterogeneous with respect to plasma lipoproteins, including apo A-I, apo B, and Lp(a).

It was suggested recently that cardiac troponins are released as T-I-C complexes and then further degraded to T and I-C. It is not known whether the various affinity to the T-I-C and I-C complex of different troponin I test systems influence the diagnostic and prognostic value of the test results in clinical practice. We studied 162 patients (61.3 S.D. 11.1 years) with suspected acute myocardial infarction (AMI) in a single center study. AMI was confirmed in 109 patients. Blood samples were taken at admission, after 1, 2, 4, 8, 12 and 24 h. Troponin I (TnI) was measured using the OPUS plus (TnI-O, cut-off 1.6 microg/l) and the Stratus II (TnI-S, cut-off 1.5 microg/l) analyzers. TnI-O has high affinity to the binary (I-C) and TnI-S to the ternary (T-I-C) troponin complex. A 6-month follow-up with respect to death and recurrent AMI was performed. The sensitivity (SE) and specificity (SP) for AMI diagnosis were 82.6 and 86.8% for TnI-S; 75.2 and 92.5% for TnI-O 0-2 h after admission. The ROC analysis showed a slightly better curve for TnI-S at 4 h (P0.05). Logistic regression analysis shows prediction of 6 months outcome by 0-24 h serial TnI-S measurements (odds ratio 5.21, P=0.0356), and serial TnI-O measurements (odds ratio 4.92, P=0.0186). High affinity to the ternary troponin complex enhances the diagnostic but not the prognostic value of a test system. Indeed, the resulting differences are small but underline the need for standardization of biochemical markers.

Background Statins are widely used drugs to reduce LDL cholesterol and risk for cardiovascular disease. Varying degrees of myopathies occur with statin use, ranging from mild myalgic symptoms alone to documented muscle damage and rhabdomyolysis. The activity of creatine kinase (CK) above a population-based reference range has been used to differentiate myalgias from documented myositic injury due to statins. However, because normal ranges for CK depend on gender, exercise, and ethnicity and are necessarily broad, it is possible for a patient to have myositic injury with a result that is within the reference range. Therefore, serial testing relative to baseline levels may be more effective in detecting mild increases in CK. Methods To properly interpret results of serial testing, we determined the biologic variation of CK and aldolase, another enzyme released from muscle, from biweekly blood collections for 8 weeks from 17 healthy subjects. Results Using log transformation, we calculated a reference change value of about + 140% and − 60% for both CK and aldolase. Conclusions The use of calculated RCV could help to improve the detection of those statin side effects promoting variation in CK values, which must be determined in clinical studies. The clinical significance of detecting more cases of statin-induced myopathy must also be examined.

The Helena REP cholesterol profile system (Helena Laboratories, Beaumont, TX) separates VLDL, LDL, HDL and Lp(a) by agarose gel electrophoresis, and quantitates cholesterol by enzymatic staining and densitometry. We compared results by electrophoresis to combined ultracentrifugation/precipitation (beta-quantification, BQ) for VLDL, LDL, and HDL cholesterol and to immunonephelometry for Lp(a) mass (Behring Diagnostics, Westwood, MA) in serum from 64 patients with a variety of lipid disorders. There was good agreement between methods, with a mean bias of -0.19 (-7.3), 0.09 (3.5), and 0.09 (3.4) mmol/l (mg/dl) for VLDL, HDL, and LDL cholesterol for electrophoresis vs. BQ. These differences were significant for HDL and VLDL cholesterol (P0.001), but not for LDL cholesterol measurement (P0.05). There was also good correlation between methods with coefficients of 0.83, 0.92, 0.91, and 0.97 for VLDL, HDL, Lp(a), and LDL, respectively. Our data indicate that this method can accurately and precisely measure LDL cholesterol directly in fresh serum from patients with a wide range of triglyceride values. However, HDL cholesterol measurement did not meet NCEP guidelines for precision and accuracy. Also, the poor resolution of VLDL and LDL in some specimens is a concern.

We reviewed the current literature in order to construct a reflex testing algorithm that maximizes clinical utility and cost-effectiveness of lipid and lipoprotein testing. The algorithm was based on the 2nd Report of the National Cholesterol Education Program Adult Treatment Panel guidelines for use of total cholesterol (TC), triglycerides (TG), HDL-C, and LDL-C, and published reports describing the clinical use of apolipoprotein B and lipoprotein (a). The success of this algorithm was tested in a low-risk general and a high-risk hyperlipidemic patient population. Lipid data and non-lipid risk factors were obtained from a national database and from patients seen at two lipid clinics. A total of 16 968 individuals from the National Health and Nutrition Examination Survey III database comprised the low-risk group, and 239 patients examined in the Hartford Hospital and Washington University Lipid Clinics comprised the high-risk group. We found a solid scientific base to support the NCEP guidelines and reasonable support for limited testing of apoB and Lp(a). According to the algorithm, the direct LDL-C assay was deemed unnecessary in 98% and 91% of low- and high-risk subjects, respectively, if one assumes that the Friedewald equation is adequate with TG≤4.00 g/l. With a more conservative cutoff of TG≤2.50 g/l, the algorithm canceled 92% and 81% of direct LDL tests, respectively. The algorithm also limited TG to 20 and 64%, apoB to 6 and 20%, and Lp(a) to 15 and 56%, of low- and high-risk groups, respectively. Use of a comprehensive, reflex algorithm for coronary heart disease risk assessment will substantially reduce the utilization of laboratory services without diminishing the clinical value of these tests. The algorithm will prevent the overuse of certain expensive tests (direct LDL) while promoting the limited use of underutilized tests [apoB and Lp(a)].

As with any new test, novel cardiac markers must meet basic analytical and clinical performance issues. For sensitivity and specificity, it is important to know what protein forms are released into blood after injury, and which of these forms are measured by the assays in question. When commercial tests become available, the choice of the measurement platform will be important in the timely delivery of results. The cut-off concentration used is also important, and requires careful selection of the patient groups to be studied. If the intent of the marker is to be used to diagnose acute myocardial infarction (AMI), data from normal subjects should not be included. However, low cut-off limits can be useful for detection of minor myocardial injury if the new assay is highly sensitive and specific. New tests are needed in the area of early diagnosis of AMI, detection of reinfarction or myocardial extension after AMI, risk stratification of patients with unstable angina, and therapeutic monitoring of patients with congestive heart failure. The most promising new markers are glycogen phosphorylase BB, free fatty acid binding protein, and brain natriuretic peptide.

Background: Laboratory tests to support the diagnosis and management of thyroid diseases have undergone significant changes with the introduction of highly sensitive assays for thyroid stimulating hormone (TSH) and free T4 and T3 concentrations in plasma. Given the importance of these measurements, quality specifications are needed to ensure accurate results. Goals for precision and accuracy are available based on known intraindividual and interindividual biological variation. Methods: Results of external quality assurance (EQA) schemes are sufficient to document precision goals but survey materials are not commutable for use in determining bias or detect the presence of unusual antibodies on a case-by-case basis. Because TSH concentrations are inversely related to free T4, this physiologic relationship can be exploited for quality assurance purposes. Results: Significant discordance between this relationship can be caused by subclinical and potentially unrecognized disease, dysequilibrium caused by recent therapy, the presence of abnormal binding proteins or protein binding competitor drugs, and antibody interferences such as human antimouse antibody (HAMA) or rheumatoid factor. Conclusion: A mechanism to automatically track discordances for subsequent follow and investigation can be an effective part of a quality assurance program for thyroid hormone measurements.