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.

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.

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 β-Trace Protein (BTP), β-Microglobulin (B2M) and cystatin C (cysC) have been developed but require validation.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.