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A letter to the editor is presented in response to an article about creatine kinase MB (CK-MB) activity.

Background: Mass spectrometry methods are emerging as tools to detect M-proteins in the serum of multiple myeloma patients with increased sensitivity and specificity compared to traditional electrophoretic methods., Methods: A liquid handling system, the Agilent AssayMAP Bravo, with liquid chromatography high-resolution quadrupole-time-of-flight (LC-QTOF) mass spectrometry to analyze intact light chains was compared to immunofixation electrophoresis (IFE) for M-protein analysis. 210 patient serum samples were analyzed in a split sample comparison (LC-QTOF vs. IFE). LC-QTOF and IFE were interpreted by different individuals in a blinded fashion and results were grouped into four categories: IFE+/QTOF+, IFE+/QTOF-, IFE-/QTOF+, or IFE-/QTOF-., Results: The LC-QTOF method is able to determine the isotype of M-proteins in a similar fashion to IFE. The estimated limit of detection was ∼ 35 mg/L for adalimumab. For split patient samples, 168 were QTOF+/IFE+, 25 were QTOF-/IFE-, 14 were QTOF+/IFE-, and three were QTOF-/IFE + . Excluding the QTOF+/IFE- results due to the improved sensitivity of the LC-QTOF method, the concordance of LC-QTOF with IFE was ∼ 98 %. The LC-QTOF method also offers improved specificity compared to electrophoretic methods due to inclusion of the accurate mass of the light chains., Conclusions: The LC-QTOF method was deemed fit for clinical use as a qualitative test with increased sensitivity and specificity compared to IFE. The LC-QTOF can also better resolve therapeutic and multiple myeloma IgG-kappa M-proteins, which present a challenge for electrophoretic methods. Future work will determine suitability of this method as an assessment of minimal residual disease status., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Canadian Society of Clinical Chemists. All rights reserved.)

Background: Delayed time from collection to centrifugation may cause erroneously high lactate levels in vitro (from continued blood cell metabolism under anaerobic conditions in the collection tube) if not collected in appropriate collection devices, consequently increasing the risk for inappropriate patient care or harm. We undertook a study to determine the turnaround time for lactate testing in a tertiary care setting and also performed short- and long-term lactate stability studies in blood collected in sodium fluoride/potassium oxalate (NaF/KOx) collection tubes., Methods: The hospital lab information system was mined for 6 months to determine patient samples that may have exceeded the time from collection-to-receival in lab of 15-min. Lactate stability was evaluated in unspun NaF/KOx collection tubes at 15 min intervals for to 2 h; and separately at 2, 6, 12, 24, and 48-h post-collection., Results: A total of 8,929 plasma samples were collected in 6 months, and 1/3 were not received in the lab within 15 min from collection. In NaF/KOx additive, lactate levels had minor increases over 2 h, and incremental increases at an average rate of 0.0035 mmol/L/h over 48 h with maximum increase of 9.8% at 48 h. However, the average change across all time points were within local allowable performance goals (at ≤4 mmol/L ± 0.5 mmol/L; at >4 mmol/L ± 12%)., Conclusion: A small proportion of lactate specimens may experience delay in processing. Although lactate levels may incrementally increase over 48-h at room temperature in unspun NaF/KOx collection tubes, the changes may not be clinically impactful., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: When applying Pierce U25 formula for estimating glomerular filtration rate (eGFR), we observed a higher proportion of eGFR < 90 mL/min/1.73 m 2 (chronic kidney disease (CKD) stage 2). We compared agreement and accuracy of the Pierce U25 (ages 2-25), Pottel (ages 2-100), and CKD-EPI (ages 18-100) formulae to GFR measurements., Methods: Post hoc analysis of the three eGFRs compared to 367 99 m technetium-diethylene-triamine penta-acetic acid ( 99 Tc DTPA) GFR measurements (240 patients) using 3 sampling points and Brockner/Mørtensen correction (body surface area calculation based on ideal weight) on simultaneous serum creatinine and cystatin C measurements., Results: Overall, the U25 formula performed well with a Spearman r of 0.8102 (95% confidence interval 0.7706 to 0.8435, p < 0.0001) while diagnostic accuracy was low in patients with normal mGFR. The U25 formula reclassified 29.5% of patients with normal mGFR as CKD stage 2; whereas the average of the modified Schwartz formula based on serum creatinine and the Filler formula based on cystatin C, only over-diagnosed CKD stage 2 in 8.5%, 24.5% within 10% and 62.7% within 30%. We therefore combined both. The average Schwartz/Filler eGFR had 36.5% of results within 10%, 84.7% within 30%, and normal mGFR accuracy was 26.8%, 63.9% for 10% and 30%, respectively, outperforming the CKD-EPI and Pottel formulae., Conclusions: The Pierce U25 formula results correlated well with mGFR < 75 mL/min/1.73 m 2 . Over the entire GFR range, accuracy was better for patients with a higher mGFR, when averaging the combined Schwartz/Filler formulae. More work is needed to prospectively confirm our findings in other centers., (© 2023. The Author(s), under exclusive licence to International Pediatric Nephrology Association.)

Background: An analytical benchmark for high-sensitivity cardiac troponin (hs-cTn) assays is to achieve a coefficient of variation (CV) of ≤ 10.0 % at the 99th percentile upper reference limit (URL) used for the diagnosis of myocardial infarction. Few prospective multicenter studies have evaluated assay imprecision and none have determined precision at the female URL which is lower than the male URL for all cardiac troponin assays., Methods: Human serum and plasma matrix samples were constructed to yield hs-cTn concentrations near the female URLs for the Abbott, Beckman, Roche, and Siemens hs-cTn assays. These materials were sent (on dry ice) to 35 Canadian hospital laboratories (n = 64 instruments evaluated) participating in a larger clinical trial, with instructions for storage, handling, and monthly testing over one year. The mean concentration, standard deviation, and CV for each instrument type and an overall pooled CV for each manufacturer were calculated., Results: The CVs for all individual instruments and overall were ≤ 10.0 % for two manufacturers (Abbott CV pooled  = 6.3 % and Beckman CV pooled  = 7.0 %). One of four Siemens Atellica instruments yielded a CV > 10.0 % (CV pooled  = 7.7 %), whereas 15 of 41 Roche instruments yielded CVs > 10.0 % at the female URL of 9 ng/L used worldwide (6 cobas e411, 1 cobas e601, 4 cobas e602, and 4 cobas e801) (CV pooled  = 11.7 %). Four Roche instruments also yielded CVs > 10.0 % near the female URL of 14 ng/L used in the United States (CV pooled  = 8.5 %)., Conclusions: The number of instruments achieving a CV ≤ 10.0 % at the female 99th-percentile URL varies by manufacturer and by instrument. Monitoring assay precision at the female URL is necessary for some assays to ensure optimal use of this threshold in clinical practice., Competing Interests: Declaration of Competing Interest The authors declare that they have no other/known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

A common practice exists in hospitals where extra tubes of blood are collected for possible add-on testing, this practice contributes to wastage of consumables. Baseline estimates from a 5-month local lab information system audit revealed that ~65 extra tubes per day were being collected, with an additional 2-week manual audit of all extra tubes received in the laboratory confirming the practice. The audits showed that the majority of the tubes (~99%) were being drawn from the adult emergency department (ED). Furthermore, only 5% of the extra tubes were being used for add-on testing, whereas the remaining tubes had no testing performed on them and were discarded at the end of the day. This translates to over 23 000 extra tubes being wasted annually.After initial discussion with ED leadership, the practice was identified as primarily nurse driven. An educational intervention was created and entitled 'Every Tube Counts', with the aim to reduce extra tube collections in the adult ED by 50% within the first month of intervention. First, a memo with initial findings and a request to stop the practice of extra tube collection was sent out to all ED staff. After 2 weeks of additional data collection, it was noticed that extra tubes were still being collected. A second intervention, which consisted of another communication and utilisation of nurse educators to disseminate the information to nursing staff, saw a remarkable ~80% reduction in collection of extra tubes in the following few months after the second intervention. The practice was followed for an additional 15 months, which saw a slight increase of extra tube collections over time with a levelling off towards the latter period of the study. However, the target goal was maintained over the entire study period., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Urinary stone disease (USD) historically has affected older men, but studies suggest recent increases in women, leading to a near identical sex incidence ratio. USD incidence has doubled every 10 years, with disproportionate increases amongst children, adolescent, and young adult (AYA) women. USD stone composition in women is frequently apatite (calcium phosphate), which forms in a higher urine pH, low urinary citrate, and an abundance of urinary uric acid, while men produce more calcium oxalate stones. The reasons for this epidemiological trend are unknown., Methods: This perspective presents the extent of USD with data from a Canadian Province and a North American institution, explanations for these findings and offers potential solutions to decrease this trend. We describe the economic impact of USD., Findings: There was a significant increase of 46% in overall surgical interventions for USD in Ontario. The incidence rose from 47.0/100,000 in 2002 to 68.7/100,000 population in 2016. In a single United States institution, the overall USD annual unique patient count rose from 10,612 to 17,706 from 2015 to 2019, and the proportion of women with USD was much higher than expected. In the 10-17-year-old patients, 50.1% were girls; with 57.5% in the 18-34 age group and 53.6% in the 35-44 age group. The roles of obesity, diet, hormones, environmental factors, infections, and antibiotics, as well as the economic impact, are discussed., Interpretation: We confirm the significant increase in USD among women. We offer potential explanations for this sex disparity, including microbiological and pathophysiological aspects. We also outline innovative solutions - that may require steps beyond typical preventive and treatment recommendations., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Filler, Dave, Ritter, Ross, Viprakasit, Hatch, Bjazevic, Burton, Gilleskie, Gilliland, Lin, Jain, McClure, Razvi, Bhayana, Wang, Coulson, Sultan, Denstedt, Fearrington and Diaz-Gonzalez de Ferris.)

High anti-GAD65 levels associate with core manifestations of GAD65 neurological autoimmunity. ELISA cut-offs for high anti-GAD65 levels (>10,000 IU/ml in serum, >100 IU/ml in CSF) have been proposed that merit further evaluation. We reviewed patients who underwent anti-GAD65 ELISA for suspected autoimmune encephalitis and found values above these cut-offs to have a positive predictive value (PPV) for neurological autoimmunity of 88%. Anti-GAD65 values above proposed ELISA cut-offs have a reasonably high PPV for neurological autoimmunity in patients with suspected autoimmune encephalitis. Consideration of alternative diagnoses and corroboration with CSF can help flag potentially clinically irrelevant results and avoid patient misdiagnosis.

Objective: The antibiotic metronidazole has been suggested to absorb light at a wavelength range commonly used in spectrophotometric assays. We sought to determine if any of the spectrophotometric assays used in our core laboratory would be susceptible to clinically significant interference from metronidazole in blood-based patient specimens., Methods: Following characterization of the absorbance spectrum for metronidazole, spectrophotometric assays involving either main or subtraction wavelengths that might be susceptible to interference from metronidazole were identified. A total of 24 chemistry tests performed on Roche cobas c502 and/or c702 instruments were evaluated for interference from metronidazole. For each assay, two pools of leftover patient serum, plasma, or whole blood specimens containing the analyte of interest at clinically relevant concentrations were prepared. Each pool was spiked with metronidazole at a final concentration of 200 mg/L (1169 µmol/L) or 10 mg/L (58 µmol/L) or the same volume of water as a control, with triplicate samples for each group. The difference in the measured analyte concentration between experimental and control groups was then compared against the total allowable error for each assay to determine whether clinically significant interference had occurred., Results: There was no significant interference observed with Roche chemistry tests due to the presence of metronidazole., Conclusion: This study provides reassurance that metronidazole is not interfering with the chemistry assays used in our core laboratory. Interference from metronidazole may be a historical problem and current spectrophotometric assays may not be susceptible due to improvements in assay design., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background: Assessment of trace and toxic element status is important for the diagnosis and monitoring of several pediatric conditions. Elemental deficiency and toxicity have serious implications, particularly in pediatrics wherein risk is higher. Pediatric reference intervals (RIs) for trace elements and normal exposure limits for toxic elements are lacking on modern analytical systems. Herein, reference values were established for 13 plasma and 22 whole blood trace elements in the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort of healthy children and adolescents., Methods: Approximately 320 healthy children and adolescents were recruited with informed consent. Trace elements were measured in whole blood and plasma samples using 2 technologies: (a) triple quadrupole inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) (n = 172) and (b) high-resolution sector field ICPMS (HR-SF-ICPMS) (n =161). RIs and normal exposure limits were then established according to Clinical and Laboratory Standards Institute guidelines., Results: Of all elements assessed, none required sex partitioning and 8 required age partitioning (e.g., copper, manganese, and cadmium). Reference value distributions determined via ICP-MS/MS and HR-SF-ICPMS demonstrated excellent concordance, with few exceptions (e.g., molybdenum, cobalt, and nickel)., Conclusions: These data represent the first study wherein pediatric RIs and normal exposure limits were derived simultaneously on 2 different clinically validated MS platforms which provide urgently needed data to inform clinical decision-making for trace elements in pediatrics. Study findings suggest some trace elements require age-specific consideration for appropriate interpretation. Highly concordant observations across the 2 analytical methods also demonstrate the comparability and reliability of results obtained on both platforms., (© American Association for Clinical Chemistry 2023. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Neural antibodies have emerged as useful biomarkers in suspected autoimmune encephalitis. We reviewed results of neural antibody testing (anti-N-methyl D-aspartate receptor (NMDAR), leucine-rich glioma-inactivated protein (LGI1), contactin-associated protein-like 2 (CASPR2), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), γ-aminobutyric acid type B receptor (GABA(B)R), dipeptidyl-peptidase-like protein-6 (DPPX), IgLON family member 5 (IgLON5) and glutamic acid decarboxylase-65 (GAD65)) using cell-based assays (CBAs) and tissue indirect immunofluorescence (TIIF) at our centre. Our findings suggest increased clinical sensitivity of CBA compared to TIIF. However, this may come at some expense to clinical specificity, as evidenced by possible false-positive results when weak serum positivity by CBA was observed for certain antibodies (i.e. anti-NMDAR, CASPR2). In such cases, correlation with serum TIIF, as well as CSF CBA and TIIF, aids in identifying true-positive results.

Background: Coronavirus Disease 2019 (COVID-19) has variable clinical presentation, from asymptomatic to severe disease leading to death. Biochemical markers may help with management and prognostication of COVID-19 patients; however, their utility is still under investigation., Methods: A retrospective study was conducted to evaluate alanine aminotransferase, C-reactive protein (CRP), ferritin, lactate, and high sensitivity troponin T (TnT) levels in 67 patients who were admitted to a Canadian tertiary care centre for management of COVID-19. Logistic, cause-specific Cox proportional-hazards, and accelerated failure time regression modelling were performed to assess the associations of initial analyte concentrations with in-hospital death and length of stay in hospital; joint modelling was performed to assess the associations of the concentrations over the course of the hospital stay with in-hospital death., Results: Initial TnT and CRP concentrations were associated with length of stay in hospital. Eighteen patients died (27%), and the median initial TnT concentration was higher in patients who died (55 ng/L) than those who lived (16 ng/L; P < 0.0001). There were no survivors with an initial TnT concentration > 64 ng/L. While the initial TnT concentration was predictive of death, later measurements were not. Only CRP had prognostic value with both the initial and subsequent measurements: a 20% increase in the initial CRP concentration was associated with a 14% (95% confidence interval (CI): 1-29%) increase in the odds of death, and the hazard of death increased 14% (95% CI: 5-25%) for each 20% increase in the current CRP value. While the initial lactate concentration was not predictive of death, subsequent measurements were., Conclusion: CRP, lactate and TnT were associated with poorer outcomes and appear to be useful biochemical markers for monitoring COVID-19 patients., (Copyright © 2021. Published by Elsevier Inc.)

BACKGROUNDThe role of humoral immunity in COVID-19 is not fully understood, owing, in large part, to the complexity of antibodies produced in response to the SARS-CoV-2 infection. There is a pressing need for serology tests to assess patient-specific antibody response and predict clinical outcome.METHODSUsing SARS-CoV-2 proteome and peptide microarrays, we screened 146 COVID-19 patients' plasma samples to identify antigens and epitopes. This enabled us to develop a master epitope array and an epitope-specific agglutination assay to gauge antibody responses systematically and with high resolution.RESULTSWe identified linear epitopes from the spike (S) and nucleocapsid (N) proteins and showed that the epitopes enabled higher resolution antibody profiling than the S or N protein antigen. Specifically, we found that antibody responses to the S-811-825, S-881-895, and N-156-170 epitopes negatively or positively correlated with clinical severity or patient survival. Moreover, we found that the P681H and S235F mutations associated with the coronavirus variant of concern B.1.1.7 altered the specificity of the corresponding epitopes.CONCLUSIONEpitope-resolved antibody testing not only affords a high-resolution alternative to conventional immunoassays to delineate the complex humoral immunity to SARS-CoV-2 and differentiate between neutralizing and non-neutralizing antibodies, but it also may potentially be used to predict clinical outcome. The epitope peptides can be readily modified to detect antibodies against variants of concern in both the peptide array and latex agglutination formats.FUNDINGOntario Research Fund (ORF) COVID-19 Rapid Research Fund, Toronto COVID-19 Action Fund, Western University, Lawson Health Research Institute, London Health Sciences Foundation, and Academic Medical Organization of Southwestern Ontario (AMOSO) Innovation Fund.

We have developed a rapid, accurate, and cost-effective serologic test for SARS-CoV-2 virus, which caused the COVID-19 pandemic, on the basis of antibody-dependent agglutination of antigen-coated latex particles. When validated using plasma samples that are positive or negative for SARS-CoV-2, the agglutination assay detected antibodies against the receptor-binding domain of the spike (S-RBD) or the nucleocapsid protein of SARS-CoV-2 with 100% specificity and ∼98% sensitivity. Furthermore, we found that the strength of the S-RBD antibody response measured by the agglutination assay correlated with the efficiency of the plasma in blocking RBD binding to the angiotensin-converting enzyme 2 in a surrogate neutralization assay, suggesting that the agglutination assay might be used to identify individuals with virus-neutralizing antibodies. Intriguingly, we found that >92% of patients had detectable antibodies on the day of a positive viral RNA test, suggesting that the agglutination antibody test might complement RNA testing for the diagnosis of SARS-CoV-2 infection., Competing Interests: S.E., C.V., and S.S.-C.L. are co-inventors in a US Provisional patent application on the agglutination assay submitted by Western University., (© 2021 The Authors.)

Aim: Review of current knowledge on assessing renal function in term and preterm neonates., Methods: Literature review and analysis of own data., Results: Prematurity, genetic, environmental and maternal factors may alter peak nephron endowment and life-long renal function. Nephrogenesis continues until 34-36 weeks of gestation, but it is altered with premature delivery. Variability of nephron endowment has a substantial impact on the clearance of renally excreted drugs. Postnatally, glomerular function rate (GFR) increases daily, doubles by two weeks, and slowly reaches full maturity at 18 months of age. Ideally, renal function biomarkers should be expressed as age-independent z-scores, and evidence suggests indexing these values to post-conceptual age rather than chronological age. Newborn and maternal serum creatinine correlate tightly for more than 72 hours after delivery, rendering this biomarker unsuitable for the assessment of neonatal renal function. Cystatin C does not cross the placenta and may be the preferred biomarker in the neonate. Here, we provide preliminary data on the natural evolution of the cystatin C eGFR in infancy., Conclusion: Cystatin C may be superior for GFR estimation in neonates, but the best approach to drug dosing of renally excreted drugs remains to be established., (©2020 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.)

Background: Autoimmunity is an increasingly recognized cause of encephalitis with a similar prevalence to that of infectious etiologies. Over the past decade there has been a rapidly expanding list of antibody biomarker discoveries that have aided in the identification and characterization of autoimmune encephalitis. As the number of antibody biomarkers transitioning from the research setting into clinical laboratories has accelerated, so has the demand and complexity of panel-based testing. Clinical laboratories are increasingly involved in discussions related to test utilization and providing guidance on which testing methodologies provide the best clinical performance., Content: To ensure optimal clinical sensitivity and specificity, comprehensive panel-based reflexive testing based on the predominant neurological phenotypic presentation (e.g., encephalopathy) is ideal in the workup of cases of suspected autoimmune neurological disease. Predictive scores based on the clinical workup can aid in deciding when to order a test. Testing of both CSF and serum is recommended with few exceptions. Appropriate test ordering and interpretation requires an understanding of both testing methodologies and performance of antibody testing in different specimen types., Summary: This review discusses important considerations in the design and selection of neural antibody testing methodologies and panels. Increased collaboration between pathologists, laboratorians, and neurologists will lead to improved utilization of complex autoimmune neurology antibody testing panels., (© American Association for Clinical Chemistry 2020. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Introduction: Testing of 25-hydroxy (25-OH) vitamin D serum levels has increased drastically in recent years and much of it is considered inappropriate based on current guidelines., Methods: In consultation with our physician groups (experts and frequent orderers), we modified existing guidelines and implemented a rational policy for 25-OH vitamin D testing and 1,25 dihydroxy (1,25 di-OH) vitamin D testing at a tertiary care centre. A computer decision support tool requiring selection of one of five acceptable testing indications was created for each test as part of a computerised physician order entry system., Results: As a result of our intervention, we observed a 27% decrease in the average monthly test volume for 25-OH vitamin D from 504±62 (mean±SD) tests per month to 370±33 (p<0.001). 1,25 di-OH vitamin D testing decreased 58% from 71±18 to 30±10 (p<0.001). The departments ordering the tests were similar during the preintervention and postintervention periods, and further audits, patient chart reviews and individualised physician feedback were required to ensure appropriate ordering of 1,25 di-OH vitamin D. The most common ordering reasons selected were malabsorption/dietary concerns (46%) for 25-OH vitamin D and renal failure (42%) for 1,25 di-OH vitamin D., Conclusions: Limitations of our computer decision support tool include a dependence on an honour system in selecting the testing indication and an inability to limit ordering frequency. Periodic monitoring of test volumes will be required to ensure adherence to guidelines. Despite these limitations, we have improved appropriate utilisation of these tests and reduced costs by approximately $C60 375 per year., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Mandatory enrichment of wheat flour in Canada with folic acid since 1998 has caused folate deficiency to be rare. There were 3019 red blood cell (RBC) folate tests performed during an 18-month period at London Health Sciences Centre (LHSC)/St. Joseph's Healthcare London (SJHC) without any folate deficiency detected. We implemented a quality improvement initiative to reduce RBC folate testing at LHSC/SJHC. We began with a retrospective review of RBC folate tests performed during the previous 18 months. We identified physicians who had ordered more than five tests during this period and sent them an educational email to inform them of our intentions and solicit their input. We then discontinued RBC folate testing in-house and a pop-up window was introduced to the computerised physician order entry system stating that biochemist approval would be needed before samples would be sent out for testing. During the audited 18-month period, the average monthly test volume was 168 (SD 20). The three departments ordering the most RBC folate testing were nephrology (15%), haematology (7%) and oncology (7%). Physician feedback was supportive of the change, and during the 2 months after targeted email correspondence, the average monthly test volume decreased 24% (p<0.01) to 128 (SD 1). On discontinuation of the test in-house and implementation of the pop-up, the average monthly test volume decreased another 74% (p<0.01) to 3 (SD 2). In the 10 months following discontinuation of the test on-site, there were only 39 RBC folate tests performed with no deficiency detected. This initiative significantly reduced unnecessary RBC folate orders. The change in ordering on email contact suggests that physician education was an important factor reducing overutilisation. However, the most significant decrease came from restricting the test so that only orders approved by a biochemist would be performed., Competing Interests: Competing interests: None declared.

Acute pancreatitis is a rapid onset of inflammation of the pancreas causing mild to severe life threatening conditions [1, 2]. In Canada, acute pancreatitis is the 5th most expensive digestive disease in Canada with a considerable economic burden on the health care system [3]. The diagnosis of acute pancreatitis is usually based on the presence of abdominal pain and elevated levels of serum amylase and/or lipase. Many health care centers use either serum amylase, lipase or both to diagnose acute pancreatitis without considering which one could provide a better diagnostic accuracy. The aim of this review is to investigate whether serum lipase alone is a sufficient biomarker for the diagnosis of acute pancreatitis. We have examined various studies looking at the utilization, sensitivity, specificity and cost associated savings of lipase and amylase in the diagnosis of acute pancreatitis. When comparing different studies, serum lipase offers a higher sensitivity than serum amylase in diagnosing acute pancreatitis. Lipase also offers a larger diagnostic window than amylase since it is elevated for a longer time, thus allowing it to be a useful diagnostic biomarker in early and late stages of acute pancreatitis. Several recent evidence-based guidelines recommend the use of lipase over amylase. Nevertheless, both lipase and amylase alone lack the ability to determine the severity and etiology of acute pancreatitis. The co-ordering of both tests has shown little to no increase in the diagnostic sensitivity and specificity. Thus, unnecessary testing and laboratory expenditures can be reduced by testing lipase alone., (Copyright © 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Objectives: To determine whether urine storage at room temperature for up to 2h versus 4h changes urinalysis results., Design and Methods: We compared the rejection rate at eight different hospital laboratories and concordance of urinalysis results (n=83; two laboratories) between urines analyzed within 2h and 4h after collection., Results: The rejection rate at the two hour cutoff was significantly higher as compared to the four hour cutoff. The concordance between urinalysis results was 97-100% between the two and four hour analyses., Conclusion: Urine may be stored for up to 4h at room temperature without significant changes to the urinalysis results., (Copyright © 2012 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

A solid phase competition-type fluoroimmunoassay for triiodothyronine (T3) uptake in serum is described. In the assay, exogenous free T3 binds to the unoccupied binding sites on serum thyroxine binding proteins while the remaining unbound T3 competes with immobilized T3 for binding to a soluble biotinylated anti-T3 monoclonal antibody. The bound biotinylated antibody is quantitated by the addition of streptavidin labeled with the europium chelator 4,7-bis(chlorosulfophenyl-1,10 phenanthroline-2,9-bicarboxylic acid (BCPDA) in the presence of excess europium. The fluorescence signal of the final complex, which is directly proportional to the number of unoccupied binding sites on thyroxine binding proteins, is then measured on the dried solid-phase with a pulsed-laser time-resolved fluorometer. The assay requires a 10 microliters serum sample and a total incubation time of 90 minutes. The coefficients of variation for within-run and between-run assays ranged from 2.0 to 5.7%. Results obtained by the present method compared well with those determined by two commercial radioimmunoassays (r greater than 0.9).

We describe a non-isotopic heterogeneous competitive immunoassay of total thyroxine in serum. Thyroxine, released from its binding proteins by merthiolate (thimerosal), competes with immobilised thyroxine (thyroxine-bovine globulin conjugate) for binding to a monoclonal biotinylated antibody. The amount of biotinylated antibody bound, which is inversely related to the amount of thyroxine in the sample, is then quantified by adding streptavidin labelled with the europium chelator 4,7-bis(chlorosulphophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (BCPDA) in the presence of excess Eu3+. The complex formed (bovine globulin-thyroxine-antibody-biotin-streptavidin-BCPDA-Eu3+) is measured on the solid-phase by time-resolved fluorescence. The assay is simple to perform and its characteristics are similar to those of other currently used immunoassay techniques.

A non-isotopic heterogeneous competitive immunoassay of serum cortisol is described. Cortisol present in the sample competes with immobilised cortisol (cortisol-thyroglobulin conjugate) for binding to a monoclonal anti-cortisol biotinylated antibody. The amount of antibody bound is measured on the dry solid-phase by time-resolved fluorometry after adding streptavidin labeled with the Eu3+ chelate 4,7-bis(chlorosulfophenyl)-1,10 phenanthroline-2,9-dicarboxylic acid (BCPDA), in the presence of excess Eu3+. The assay is simple to perform, its characteristics are similar to those of radioimmunoassay techniques, and is suitable for routine clinical use.

Detailed evidence for the amino acid sequence of allosteric citrate synthase from Escherichia coli is presented. The evidence confirms all but 11 of the residues inferred from the sequence of the gene as reported previously [Ner, S. S., Bhayana, V., Bell, A. W., Giles, I. G., Duckworth, H. W., & Bloxham, D. P. (1983) Biochemistry 22, 5243]; no information has been obtained about 10 of these (residues 101-108 and 217-218), and we find aspartic acid rather than asparagine at position 10. Substantial regions of sequence homology are noted between the E. coli enzyme and citrate synthase from pig heart, especially near residues thought to be involved in the active site. Deletions or insertions must be assumed in a number of places in order to maximize homology. Either of two lysines, at positions 355 and 356, could be formally homologous to the trimethyllysine of pig heart enzyme, but neither of these is methylated. It appears that E. coli and pig heart citrate synthases are formed of basically similar subunits but that considerable differences exist, which must explain why the E. coli enzyme is hexameric and allosterically inhibited by NADH, while the pig heart enzyme is dimeric and insensitive to that nucleotide.

A non-isotopic heterogeneous non-competitive immunoassay for carcinoembryonic antigen is described. CEA present in serum binds simultaneously to two monoclonal antibodies specific for different antigenic determinants of CEA. One antibody is immobilized on a solid-phase (microtiter well) and the other is biotinylated. The amount of biotinylated antibody bound is measured on the dried solid-phase by time-resolved fluorometry after adding streptavidin labeled with the europium chelate 4,7-bis(chlorosulfophenyl)-1,10 phenanthroline-2, 9-dicarboxylic acid (BCPDA) in the presence of excess Eu3+. The assay is simple to perform, its characteristics are similar to those of other isotopic and non-isotopic techniques, and it is suitable for routine clinical use.