Canadian Society of Clinical Chemists Harmonized Pediatric Lipid Reporting Recommendations for Clinical Laboratories.

Detecting dyslipidemia early is important because atherosclerosis originates in childhood and early treatment can improve outcomes. In 2022, the Canadian Cardiovascular Society (CCS) and Canadian Pediatric Cardiology Association (CPCA) published a clinical practice update to detect, evaluate, and manage pediatric dyslipidemia. However, guidance on its translation into clinical laboratories is lacking. The Canadian Society of Clinical Chemists Working Group on Reference Interval Harmonization Lipid Team aims to assist guideline implementation and promote harmonized pediatric lipid reporting across Canada. The 2022 CCS/CPCA clinical practice update, 2011 National Heart, Lung, and Blood Institute integrated guidelines, and new data analysis (Canadian pediatric reference values from the Canadian Laboratory Initiative on Pediatric Reference Intervals [CALIPER] and retrospective patient data from large community laboratories) were incorporated to develop 5 key recommendations. These include recommendations to: (1) offer nonfasting and fasting lipid testing; (2) offer a lipid panel including total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), non-HDL-C, and triglycerides, with apolipoprotein B and lipoprotein(a) available as individually orderable tests; (3) flag total cholesterol, LDL-C, and non-HDL-C results ≥ 95th percentile, and HDL-C results < 10th percentile, as recommended by CCS/CPCA/National Heart, Lung, and Blood Institute and validated by CALIPER, and flag apolipoprotein B and nonfasting triglyceride results ≥ 95th percentile on the basis of CALIPER, and do not flag Lp(a) results but mention the adult cutoff in the interpretive comments; (4) implement interpretive comments listed in the current report; and (5) implement the National Institutes of Health LDL-C equation. The Canadian Society of Clinical Chemists Working Group on Reference Interval Harmonization Lipid Team will support clinical laboratories to implement these recommendations using knowledge translation strategies. Harmonizing pediatric lipid reporting across Canadian clinical laboratories will optimize clinical decision-making and improve cardiovascular risk management in youth.

Parathyroid hormone measurement in chronic kidney disease: Impact of inter-method variability on mineral bone disease assessment.

BACKGROUND: Parathyroid hormone (PTH) is measured routinely as part of Chronic Kidney Disease Bone and Mineral Disorders (CKD-MBD) assessment. Multiple PTH assays exist with known differences resulting in CKD-MBD guidelines recommending treatment based on assay-specific thresholds. The study objectives are to assess between manufacturer and within manufacturer variability of PTH assays and the impact of assay variability on the assessment of CKD-BMD using both vendor defined and empirically derived thresholds. METHODS: Data were collected from Ontario, Canada's Proficiency Testing Program (24 challenge vials, 115-133 laboratories all using secondary generation PTH assays. Mean PTH and precision by the coefficient of analytical variation (CVa) were calculated. For each vial, whether the manufacturer's mean value exceeded the vendor-defined and empirically-derived upper limit of normal (ULN) was recorded and the concordance between assays was determined. RESULTS: Across all laboratories, the mean PTH range was 12.0 ± 3.9 pmol/L and the mean CVa was 30%. The percent of vials with a mean PTH exceeding manufacturer's specific ULN varied substantially between manufacturers. Only 58% of vials had complete concordance as to whether mean PTH was above assay-specific ULNs. This increased to 83% using the empirically derived ULN. CONCLUSIONS: CKD-BMD assessment and management will depend on the PTH assay. The between-assay variability is reduced but not eliminated when empirically derived reference intervals are used. Improvements in PTH measurement are required in order to ensure consistent patient care.

Comparison of the new and traditional CKD-EPI GFR estimation equations with urinary inulin clearance: A study of equation performance.

BACKGROUND: Diagnosis, prognostication and treatment in chronic kidney disease is often informed by an estimate of the glomerular filtration rate (GFR). Commonly used GFR estimation (eGFR) equations are based on serum creatinine (Cr) concentrations and display suboptimal precision and accuracy. Newer equations incorporating additional endogenous markers such as ß-Trace Protein (BTP), ß2-Microglobulin (B2M) and cystatin C (cysC) have been developed but require validation. METHODS: This prospective cohort study evaluated the performance of 6 eGFR equations developed by the chronic kidney disease - epidemiology collaboration group (CKD-EPI) against urinary inulin clearance GFR in patients recruited from outpatient nephrology clinics. RESULTS: Mean biases were negligible and similar between equations. The eGFR-EPI Cr/cysC had the best precision and accuracy of all the equations and the best agreement with inulin mGFR when classifying participants into GFR categories. The BTP and B2M equations displayed the worst precisions and accuracies and showed the least consistent performance across levels of GFR. Thus, the eGFR-EPI Cr/cysC is the least biased, most precise and has the highest accuracy as compared to other eGFR-EPI equations. CONCLUSIONS: The BTP and B2M equations are the worst performing of the eGFR-EPI equations, and no benefit is observed with the addition of BTP or B2M to Cr/cysC.

National Survey of Adult and Pediatric Reference Intervals in Clinical Laboratories across Canada: A Report of the CSCC Working Group on Reference Interval Harmonization.

OBJECTIVE: Reference intervals are widely used decision-making tools in laboratory medicine, serving as health-associated standards to interpret laboratory test results. Numerous studies have shown wide variation in reference intervals, even between laboratories using assays from the same manufacturer. Lack of consistency in either sample measurement or reference intervals across laboratories challenges the expectation of standardized patient care regardless of testing location. Here, we present data from a national survey conducted by the Canadian Society of Clinical Chemists (CSCC) Reference Interval Harmonization (hRI) Working Group that examines variation in laboratory reference sample measurements, as well as pediatric and adult reference intervals currently used in clinical practice across Canada. DESIGN AND METHODS: Data on reference intervals currently used by 37 laboratories were collected through a national survey to examine the variation in reference intervals for seven common laboratory tests. Additionally, 40 clinical laboratories participated in a baseline assessment by measuring six analytes in a reference sample. RESULTS: Of the seven analytes examined, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and creatinine reference intervals were most variable. As expected, reference interval variation was more substantial in the pediatric population and varied between laboratories using the same instrumentation. Reference sample results differed between laboratories, particularly for ALT and free thyroxine (FT4). Reference interval variation was greater than test result variation for the majority of analytes. CONCLUSION: It is evident that there is a critical lack of harmonization in laboratory reference intervals, particularly for the pediatric population. Furthermore, the observed variation in reference intervals across instruments cannot be explained by the bias between the results obtained on instruments by different manufacturers.

Creatinine Assay Attainment of Analytical Performance Goals Following Implementation of IDMS Standardization: Further Improvements Required.

BACKGROUND: The international initiative to standardize creatinine (Cr) assays by tracing reference materials to Isotope Dilution Mass Spectrometry (IDMS) assigned values was implemented to reduce interlaboratory variability and improve assay accuracy. OBJECTIVE: The aims of this study were to examine whether IDMS standardization has improved Cr assay accuracy (bias), interlaboratory variability (precision), total error (TE), and attainment of recommended analytical performance goals. METHODS: External Quality Assessment (EQA) data (n = 66 challenge vials) from Ontario, Canada, were analyzed. The bias, precision, TE, and the number of EQA challenge vials meeting performance goals were determined by assay manufacturer before (n = 32) and after (n = 34) IDMS implementation. RESULTS: The challenge vials with the worst bias and precision were spiked with known common interfering substances (glucose and bilirubin). IDMS standardization improved assay bias (10.4%-1.6%, P < .001), but precision remained unchanged (5.0%-4.7%, P = .5) with performance goals not consistently being met. Precision and TE goals based on biologic variation were attained by only 29% to 69% and 32% to 62% of challenge vials. CONCLUSIONS: While IDMS standardization has improved Cr assay accuracy and thus reduced TE, significant interlaboratory variability remains. Contemporary Cr assays do not currently meet the standards required to allow for accurate and consistent estimated glomerular filtration rate assessment and chronic kidney disease diagnosis across laboratories. Further improvements in Cr assay performance are needed.

MISE EN CONTEXTE: L'initiative internationale visant à standardiser les épreuves de dosage de la créatinine par le traçage des substances de référence aux valeurs qui leur sont assignées par spectrométrie de masse à dilution isotopique (IDMS) a été mise en œuvre dans le but de réduire la variabilité inter-laboratoires et d'améliorer la précision de l'essai lui-même. OBJECTIFS DE L'ÉTUDE: Cette étude visait à déterminer si la standardisation par IDMS parvenait à améliorer l'exactitude de l'épreuve de dosage de la créatinine (biais), à réduire la variabilité inter-laboratoires (précision) et si elle contribuait à l'atteinte des objectifs recommandés en matière de performance analytique. MÉTHODOLOGIE: On a analysé les données de l'assurance externe de la qualité (AEQ) provenant de l'Ontario, au Canada. Le biais, l'exactitude, l'erreur totale ainsi que le nombre de fioles d'épreuves provenant du AEQ atteignant les objectifs d'erreurs ont été déterminés par le fabricant de l'épreuve avant et après la mise en œuvre de l'IDMS. RÉSULTATS: Les essais enzymatiques ont obtenu des résultats plus précis et des valeurs d'erreur totale inférieures. Les fioles d'épreuves qui présentaient la plus faible précision et le plus fort biais étaient celles à qui l'on avait ajouté des substances connues pour créer de l'interférence (glucose et bilirubine). La standardisation par IDMS a permis d'améliorer le biais lié à l'épreuve (de 10,4% à 1,6%, P < 0,001), mais n'a pas affecté la précision qui est demeurée faible (5,0 à 4,7%, P = 0,5). De plus, les objectifs de performance n'ont pas toujours été atteints: les objectifs de précision et d'erreur totale établis en tenant compte des variations biologiques ont été atteints par seulement 29 à 69% et 32 à 62% des fioles d'épreuves. CONCLUSIONS: Bien que la standardisation par IDMS ait réduit les valeurs d'erreur totale obtenues lors des épreuves de dosage de la créatinine et ait amélioré la précision de l'essai, une variabilité inter-laboratoires significative subsiste dans les résultats. À ce jour, les épreuves de dosage de la créatinine ne rencontrent toujours pas les standards exigés pour permettre une mesure précise et homogène du débit de filtration glomérulaire estimé et le diagnostic de l'insuffisance rénale chronique dans tous les laboratoires. Par conséquent, des améliorations supplémentaires en ce qui concerne la performance des épreuves de dosage de la créatinine s'avèrent nécessaires.

Interlaboratory Variability in Plasma Creatinine Measurement and the Relation with Estimated Glomerular Filtration Rate and Chronic Kidney Disease Diagnosis.

BACKGROUND AND OBJECTIVES: The tracing of creatinine (Cr) reference materials to isotope dilution mass spectrometry-assigned values was implemented worldwide to reduce interlaboratory variability and improve assay accuracy. The aims of this study were to examine the current extent of interlaboratory variability and its effect on eGFR. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Leftover plasma from 2-3 consecutive days was obtained from 53 intensive care unit patients with a range of kidney functions. Individual patient samples were pooled and split and sent to 12 different laboratories for Cr measurement. For each patient, the mean Cr and Chronic Kidney Disease Epidemiology Collaboration eGFR (eGFR-EPI), assuming a 65-year-old nonblack woman, were determined. Interlaboratory variability was assessed by the range and SD of Cr and eGFR-EPI. This was repeated after stratifying by assay type and by the median Cr of 1.36 mg/dl. For patients whose eGFR-EPI range included 60 ml/min per 1.73 m2, the percentage of laboratories with eGFR-EPI<60 ml/min per 1.73 m2 was determined. RESULTS: The mean±SD of the Cr and eGFR-EPI ranges were 0.20±0.09 mg/dl and 14±9 ml/min per 1.73 m2 for Cr<1.36 mg/dl. Jaffe Cr results were an average 0.1 mg/dl (Cr≥1.36 mg/dl) and 0.05 mg/dl (Cr<1.36 mg/dl) higher than enzymatic results (P<0.001 for both). Ten patients had an eGFR-EPI range that included 60 ml/min per 1.73 m2. Their median eGFR-EPI range was 15 ml/min per 1.73 m2. There was significant discordance in the diagnosis of CKD (eGFR-EPI<60 ml/min per 1.73 m2), with laboratories using Jaffe Cr methods making the diagnosis more frequently than those using enzymatic Cr methods (60% versus 39%). CONCLUSIONS: Significant interlaboratory variability in Cr measurement still exists. Jaffe assays yield higher Cr values than enzymatic assays, leading to lower eGFR-EPIs and more frequent CKD diagnoses. Further improvements in assay performance are required to standardize patient CKD diagnosis and to facilitate longitudinal Cr monitoring across laboratories.

A critical appraisal of accuracy and cost of laboratory methodologies for the diagnosis of hypogonadism: the role of free testosterone assays.

The biochemical diagnosis of male hypogonadism remains a controversial issue. The problem is compounded by the variety of laboratory assays available to measure serum testosterone (T) and the limited understanding, among clinicians, of their relative diagnostic validity. It is widely accepted that only the testosterone not bound to sex hormone-bounding globulin is metabolically active. Therefore, for diagnostic purposes it is frequent practice to order the measurement of free T (FT) or bioavailable T (BAT). Our objective is to describe the methods available for measuring FT and to review the literature to determine the relevance of ordering FT as a diagnostic laboratory tool in cases of suspected hypogonadism. We also provide our biochemical approach in evaluating men with T deficiency. The limited information available in this regard is frequently confined to the biochemistry literature. The few reliable studies indicate that analog-based measurement of FT offers no diagnostic or financial advantage over automated assay for total T. The manuscript also describes "How we do it." For optimal diagnostic accuracy and financial responsibility, total T and calculated FT (cFT) should be the tests employed for initial and confirmatory diagnosis respectively. Measurement of bioavailable T is an alternative option but not germane to the points to which we are calling attention in this paper. While clinicians should be discouraged from ordering FT assays, laboratories performing it should indicate what method was used and warned about possible reliability concerns. FT assays should no longer be a reimbursable test.

Folic acid transport to the human fetus is decreased in pregnancies with chronic alcohol exposure.

BACKGROUND: During pregnancy, the demand for folic acid increases since the fetus requires this nutrient for its rapid growth and cell proliferation. The placenta concentrates folic acid into the fetal circulation; as a result the fetal levels are 2 to 4 times higher than the maternal level. Animal and in vitro studies have suggested that alcohol may impair transport of folic acid across the placenta by decreasing expression of transport proteins. We aim to determine if folate transfer to the fetus is altered in human pregnancies with chronic alcohol consumption. METHODOLOGY/PRINCIPAL FINDINGS: Serum folate was measured in maternal blood and umbilical cord blood at the time of delivery in pregnancies with chronic and heavy alcohol exposure (n = 23) and in non-drinking controls (n = 24). In the alcohol-exposed pairs, the fetal:maternal serum folate ratio was ≤ 1.0 in over half (n = 14), whereas all but one of the controls were >1.0. Mean folate in cord samples was lower in the alcohol-exposed group than in the controls (33.15 ± 19.89 vs 45.91 ± 20.73, p = 0.04). CONCLUSIONS/SIGNIFICANCE: Our results demonstrate that chronic and heavy alcohol use in pregnancy impairs folate transport to the fetus. Altered folate concentrations within the placenta and in the fetus may in part contribute to the deficits observed in the fetal alcohol spectrum disorders.

FGF-23 is associated with cardiac troponin T and mortality in hemodialysis patients.

Fibroblast growth factor 23 (FGF-23) is elevated in patients with end-stage kidney disease and has been linked with mortality, vascular calcification, markers of bone turnover, and left ventricular hypertrophy. In this cohort study, we determined the correlates of FGF-23 (including cardiac troponin T [cTNT]) and determined its association with mortality over 3.5 years of follow-up in 103 prevalent hemodialysis patients. Mean age was 61.2 (15.5) and the mean dialysis vintage was 4.19 years (4.6). The median (interquartile range) FGF-23 was 1259 (491, 2885) RU/mL. Independent predictors (estimate standard error) of log-transformed FGF-23 concentrations included phosphorus (0.75 [0.237], P = 0.002) and cardiac troponin T (1.04 [0.41], P = 0.01). There were 57 deaths. In the fully adjusted model, the significant predictors of mortality included age and albumin. The independent association between FGF-23 and cTNT is a novel finding. Whether this relationship supports the possibility that a downstream effect of dysregulated phosphorous homeostasis may be enhanced cardiac remodeling requires further study.

The impact of interlaboratory differences in cystatin C assay measurement on glomerular filtration rate estimation.

BACKGROUND AND OBJECTIVES: Cystatin C (CysC) is a promising marker of GFR. Several equations have been derived to estimate GFR from its serum concentration. Heterogeneity in the performance of these equations exists in validation studies even when the same CysC assay from the same manufacturer is utilized. This study was designed to examine the differences in CysC and GFR estimation (eGFR) using Siemens' nephelometric immunoassay and the Mayo Clinic equation. The ability of the eGFRs to predict measured GFR was also examined. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Ninety-seven split samples were sent to laboratories at Children's Hospital of Eastern Ontario (CHEO) in Ottawa, Canada, and at the Mayo Clinic in Rochester, Minnesota. RESULTS: The mean CHEO CysC was 0.17 mg/L (10%) lower than the mean Mayo Clinic CysC. Using the Mayo Clinic equation, the mean eGFR difference was 7.2 ml/min per 1.73 m(2) (15%). Approximately 36% of the results agreed within 10%, while 13% were discordant by greater than 30%. Larger absolute differences in mean eGFR between the two laboratories were found in the subgroup with CysC less than 1.41 mg/L as compared with the subgroup greater than 1.41 mg/L (9.5 versus 5.0 ml/min per 1.73 m(2)). Correction of CHEO values to the Mayo Clinic did not improve GFR estimation. CONCLUSIONS: Significant differences in CysC measurement exist between laboratories using the same assay by the same manufacturer and these lead to clinically relevant differences in GFR estimation. This interlaboratory variability needs to be recognized when interpreting and comparing CysC and eGFR results.

Chronic ethanol exposure and folic acid supplementation: fetal growth and folate status in the maternal and fetal guinea pig.

Chronic ethanol exposure (CEE) can produce developmental abnormalities in the CNS of the embryo and developing fetus. Folic acid (FA) is an important nutrient during pregnancy and low folate status exacerbates ethanol-induced teratogenicity. This study tested the hypotheses that (1) CEE depletes folate stores in the mother and fetus; and (2) maternal FA supplementation maintains folate stores. CEE decreased fetal body, brain, hippocampus weights, and brain to body weight ratio but not hippocampus to body weight ratio. These effects of CEE were not mitigated by maternal FA administration. The FA regimen prevented the CEE-induced decrease of term fetal liver folate. However, it did not affect maternal liver folate or fetal RBC folate at term, and did not mitigate the nutritional deficit-induced decrease of term fetal hippocampus folate. This study suggests that maternal FA supplementation may have differential effects on folate status in the mother and the fetus.

The significance of biological variation in the diagnosis of testosterone deficiency, and consideration of the relevance of total, free and bioavailable testosterone determinations.

PURPOSE: The diagnosis of testosterone deficiency syndrome is based on clinical manifestations and documentation of low testosterone. Which biochemical tests to use and the importance of morning sampling are still controversial. Biological variation (including interindividual and intraindividual biological variation) must be considered when interpreting individual results as it determines the usefulness of reference intervals and the change (reference change value) necessary for a significant difference between results. MATERIALS AND METHODS: A total of 87 healthy men (50 to 70+ years old) provided blood in the morning of the first day, and 4 weeks later in the morning and afternoon. Samples were frozen (-70C) and analyzed in the same run for serum testosterone, sex hormone-binding globulin and albumin, and bioavailable testosterone and free testosterone were calculated. RESULTS: Serum testosterone was lower in the afternoon by 1.5 nmol/l (43 ng/dl, p <0.05), with larger changes observed with higher morning values. However, this diurnal effect was dwarfed by the normal biological variation observed for repeat morning samples (serum testosterone +/- 4 nmol/l [115 ng/dl]). Between day intra-individual biological variation for morning serum testosterone was 18.7% while within day intra-individual biological variation was 12.9%. A change of 52% (reference change value) is necessary between serial morning results to confirm a significant difference. The biological variation parameters of calculated bioavailable testosterone and calculated free testosterone confer no advantage over total testosterone. CONCLUSIONS: Marked individuality of serum testosterone is evident even in healthy men. Because intraindividual biological variation is less than interindividual biological variation, reference intervals are marginally useful. The homeostatic set point of a patient could decrease by half and still be within the reference interval. Prospective establishment of an individual's baseline over repeated measurements or symptoms regardless of serum testosterone concentration should be used to guide clinical decisions.

Hyperinflation-induced cardiorespiratory failure in rats.

We previously showed that severe inspiratory resistive loads cause acute (<1 h) cardiorespiratory failure characterized by arterial hypotension, multifocal myocardial infarcts, and diaphragmatic fatigue. The mechanisms responsible for cardiovascular failure are unknown, but one factor may be the increased ventricular afterload caused by the large negative intrathoracic pressures generated when breathing against an inspiratory load. Because expiratory threshold loads increase intrathoracic pressure and decrease left ventricular afterload, we hypothesized that anesthetized rats forced to breathe against such a load would experience only diaphragmatic failure. Loading approximately doubled end-expiratory lung volume, halved respiratory frequency, and caused arterial hypoxemia and hypercapnia, respiratory acidosis, and increased inspiratory drive. Although hyperinflation immediately reduced the diaphragm's mechanical advantage, fatigue did not occur until near load termination. Mean arterial pressure progressively fell, becoming significant (cardiovascular failure) midway through loading despite tachycardia. Loading was terminated (endurance 125 +/- 43 min; range 82-206 min) when mean arterial pressure dropped below 50 mmHg. Blood samples taken immediately after load termination revealed hypoglycemia, hyperkalemia, and cardiac troponin T, the last indicating myocardial injury that was, according to histology, mainly in the right ventricle. This damage probably reflects a combination of decreased O(2) delivery (decreased venous return and arterial hypoxemia) and greater afterload due to hyperinflation-induced increase in pulmonary vascular resistance. Thus, in rats breathing at an increased end-expiratory lung volume, cardiorespiratory, not just respiratory, failure still occurred. Right heart injury and dysfunction may contribute to the increased morbidity and mortality associated with acute exacerbations of obstructive airway disease.

Potential impact of N-terminal pro-BNP testing on the emergency department evaluation of acute dyspnea.

OBJECTIVES: Measurement of the serum B-type natriuretic peptide (BNP) level and more recently its precursor, N-terminal proBNP (NT-proBNP), has been advocated to facilitate the diagnosis of heart failure in the emergency department (ED). We sought to determine the potential impact of adding NT-proBNP testing to the routine evaluation of emergency patients with acute dyspnea. METHODS: This prospective cohort study enrolled a convenience sample of acutely dyspneic patients at a tertiary care ED. We excluded trauma patients and those under 30 years of age. Patients underwent standard evaluation, including radiography when indicated. At the point of final diagnosis and blinded to the NT-proBNP result, physicians documented the likelihood that heart failure accounted for the patient's acute dyspnea on a 7-point Likert scale, the data from which was subsequently collapsed to 3 categories for analysis purposes. The primary outcome was the agreement between clinical impression and the NT-proBNP assay classified using manufacturer-recommended, age-specific cut-offs. Newly proposed cut-offs from a recent study were also evaluated. RESULTS: One hundred and twenty-nine patients making 139 ED visits were enrolled (median age 76 years; 59% admitted). The serum NT-proBNP assay was positive in 119 (86%, 95% confidence interval [CI] 80%-91%) cases, including 75% (43/57, 95% CI 62%-86%) of the cases that the treating physician felt were not caused by heart failure, and 86% (25/29, 95% CI 68%-96%) where the treating physician was unsure. The median NT-proBNP concentration was higher in patients clinically believed to have heart failure rather than pneumonia or chronic obstructive pulmonary disease; however, the ranges of these values overlapped extensively (median 4361 pg/mL; interquartile range [IQR] 2386-10877 v. 1651 pg/mL; IQR 370-4745, respectively). CONCLUSIONS: There is high discordance between the clinical impression of treating physicians and NT-proBNP concentrations, notably in patients who are believed not to have heart failure. Although the reference standard of ED diagnosis is imperfect, the broad overlap in NT-proBNP concentrations suggests poor specificity in this target patient population. The introduction of routine ED NT-proBNP testing using the current cut-offs would be expected to result in substantial indirect costs from further diagnostic testing. It remains unclear whether the introduction of this diagnostic test would have a positive impact on clinically relevant patient outcomes.

Screening urine for drugs of abuse in the emergency department: do test results affect physicians' patient care decisions?

BACKGROUND: Drug abuse is a frequent factor in emergency department (ED) visits. Although commonly performed, qualitative testing of urine for drugs of abuse (u-DOA) is inherently limited in its ability to establish the identity, timing or dose of substances used. Previous studies have demonstrated these limitations, but their designs cannot be used to determine whether the results of u-DOA tests affect physicians' patient care decisions. Our objective was to determine the impact of u-DOA testing on the care of patients who present to the ED. METHODS: All adults 18 years of age or older who had u-DOA testing in 2 urban teaching EDs were eligible. Victims of vehicular trauma or sexual assault were excluded. Just prior to communicating the results of u-DOA testing for a patient, an investigator interviewed the ordering physician or consultant physician about the patient care plans for that patient. Test results were then revealed, and the questions immediately repeated. This design isolated the impact of knowledge of u-DOA test results on physicians' patient care decisions. Any intended changes in patient care plans reported by the interviewed physician were compared to a priori criteria for substantive change and then subsequently reviewed by an independent expert to determine whether that change was justified. RESULTS: Of the 110 u-DOA test results studied and the resultant 133 opportunities to influence physician management plans, there were 4 reported changes in management. One management change was judged to be substantive, but none of the 4 reported changes were considered by the independent expert reviewer to be justified. Urine-DOA testing thus led to a justified change in management in 0/133 instances (95% confidence interval 0%-2.3%). CONCLUSIONS: Urine-DOA is rarely helpful in guiding patient care decisions in the ED. The results of this study call into question the need for this test in the ED setting.

Medical students' perceptions of an undergraduate research elective.

Recent years have seen a steady decline in the number of new physician-investigators (Association of American Medical Colleges, 2000). To encourage medical students to select research careers, the Queen's University Faculty of Health Sciences curriculum includes a mandatory Critical Enquiry elective in the 2nd year. An anonymous written survey was administered to medical students before and after the elective to determine their perceptions of the value of the elective and its impact on their decision to pursue a career in medical research. There was a significant increase in the number of students expressing an interest in pursuing a research career following the elective (35-42%, p = 0.029). Students recognized other benefits including the development of critical appraisal, information literacy, and critical thinking skills; and the opportunity to select an area of and form contacts for postgraduate training. Even students who choose not to pursue careers in medical research perceive benefits to a mandatory undergraduate research elective.

Salivary cortisol on ROCHE Elecsys immunoassay system: pilot biological variation studies.

OBJECTIVES: Salivary analysis is a noninvasive alternative that may be more acceptable to patients, especially children. As such, it has the potential for incorporation into comprehensive, dynamic investigations of metabolic dysfunctions - a significant advancement over a single time point serum analysis. In this study, we wanted to determine if the serum cortisol assay on our routine immunoassay analyzer could reliably measure salivary cortisol concentrations. Because of potential fluctuations in salivary concentrations, we included a biologic variation study as a main facet of our preliminary method evaluation. DESIGN AND METHODS: Twenty-eight healthy individuals (12 males, 16 females) volunteered to provide 5 nonconsecutive first morning saliva samples over a two-week period. Samples were stored frozen at home until the completion of the study. Following thawing and centrifugation, cortisol was measured in batch mode for each set of participant samples on the ROCHE Elecsys. Biologic variation was determined following removal of outliers. A method comparison was performed with the DPC Coat-A-Count Cortisol assay following the recommended modifications for salivary analysis, and with the Salimetrics HS-Cortisol two-site monoclonal assay optimized for salivary cortisol. RESULTS: Mean salivary cortisol concentration was 20.4 nmol/L. Analytical variation (CV(A) = 3.8%), within-subject variation (CV(I) = 6.3%), between-subject variation (CV(G) = 20.5%), index of individuality (II = 0.36) and reference change value (RCV = 20.4%) were determined. A negative 40% proportional bias was observed on the Elecsys compared to the two methods that have already been optimized for salivary analysis. CONCLUSIONS: This study demonstrated that salivary cortisol can be reliably measured on a routine automated immunoassay analyzer such as the ROCHE Elecsys. This particular assay needs to be optimized at the low end of the standard curve for routine use with salivary samples. Based on the relatively small intra-individual variation and low index of individuality, reference change values are preferable to the use of population reference intervals for this assay.

Proficiency testing performance: a case study with modeling.

OBJECTIVES: Previous literature has approached proficiency testing (PT) performance by defining the minimum levels, and combinations of imprecision and bias, necessary to meet PT requirements. In this case report, current PT performance was assessed and modeling performed to prioritize our quality improvement efforts. METHODS: A total of 1,006 chemistry challenge results from Ontario's Laboratory Proficiency Testing Program (LPTP, now QMPLS) performed on 69 tests during 1999 and 2000 were used for this retrospective analysis. Peer group means, all method means and results from reference labs were used for comparison. QMPLS flagging and recommended performance criteria were compiled, and modeling performed to predict different levels of performance. RESULTS: Our internal imprecision is <5% for 72% of our 69 tests; however, only 20% of our tests had a CV/PT <25%. Of the 1,006 challenges performed, 136 (13.5%) results were outside PT limits, 55 (5.5%) results were flagged, and 12 requests were received from QMPLS seeking clarification on 24 (2.4%) results. Follow-up identified 9 (38%) nonanalytical errors, 8 (33%) method bias errors, 4 (17%) random errors, 2 poor methods, and one with no error identified. Modeling predicted flagging rates of 2.4% using QMPLS recommended precision performance, 1.6% using our current internal imprecision, 2.2% or 7.0% if we included an overall 20% or 50% relative bias rate with our current imprecision levels, or 15.0% when an estimate of our actual bias for each analyte was considered along with our current imprecision levels. CONCLUSIONS: If imprecision were the only cause of PT errors, our flagging rate for this study period would be 1.6%, and we would need to formally investigate 8 results a year. In practice, strict application of the QMPLS PT criteria would result in 68 investigations annually; however, judicial review of the results before request for clarification significantly reduced this number to 12 investigations (of which 38% were nonanalytical errors). At the present time bias is a significant cause of poor PT performance in a variety of assays. Individual laboratories need to address the problem of bias, and ultimately so do manufacturers. It would be helpful if PT programs also acknowledged this necessary evolution in both their criteria and processes.