INTRODUCTION:The novel biomarker Proenkephalin A 119-159 (PENK) has emerged as a promising marker of kidney function, with the potential to perform comparably to invasive gold-standard methods. This study provides the first reference values for PENK in a German pediatric and young adult cohort, with a particular focus on age-specific values. MATERIALS AND METHODS:PENK was measured in serum using a double-monoclonal sandwich immunoassay in a cohort of individuals aged 1 month-40 years. The study included 221 participants, comprising 188 pediatric participants (< 18 years) and 33 adults (≥ 18 years). The upper reference limit was defined as the estimated 97.5th percentile derived using quantile regression with lambda-mu-sigma (LMS). RESULTS:Serum PENK concentrations declined with age during the first 20 years of life. In the combined-sex cohort, the estimated 97.5th percentile decreased from 618 pmol/L in the first month of life to 103 pmol/L at age 20 years. Thereafter, the 97.5th percentile remained stable in young adults (>20 years), ranging from 86 to 93 pmol/L. Similarly, the estimated 50th percentile declined from 346 pmol/L in the first month of life to 58 pmol/L at age 20 years, remaining stable thereafter at 48-52 pmol/L. No statistically significant differences in PENK concentrations were observed between females and males within the respective age groups. CONCLUSIONS:This study provides the first age-dependent reference values for PENK. These reference values are a prerequisite for future studies evaluating the precision and clinical utility of PENK as a diagnostic biomarker across all age groups, particularly in pediatric populations.
INTRODUCTION:We evaluated lipoprotein(a) [Lp(a)] repeat testing patterns, inter-measurement intervals, department-specific repeat testing rates, and the clinical significance of changes between repeat measurements using asymmetric reference change values (RCV) and risk-category reclassification. MATERIALS AND METHODS:All Lp(a) results from 1 April 2024 to 1 April 2026 at a tertiary hospital laboratory in Istanbul, Türkiye, were retrospectively extracted. Results were classified as low (<0.3 g/L), intermediate (0.3-0.5 g/L), or high (>0.5 g/L). The asymmetric RCV, calculated using an individual biological variation coefficient of 10.2% (EFLM Biological Variation Database) and analytical variation coefficient of 3.6% (internal quality control), were + 34.9% and - 25.9%. Pearson chi-square tests and Wilson 95% confidence intervals were applied. RESULTS:Among 1623 patients with 1730 results, 96 (5.9%) underwent repeat testing, generating 107 consecutive pairs. Median inter-measurement interval was 156 days (IQR 71-234). Repeat testing rates did not differ by initial category (low 5.7%, intermediate 8.1%, high 5.3%; χ2 = 1.693, p = 0.429). RCV exceedance occurred in 23.4% (95% CI 16.4-32.2%), clinical reclassification in 11.2% (95% CI 6.5-18.6%), and both in 5.6% (95% CI 2.6-11.7%). RCV exceedance by baseline category was 20.8%, 33.3%, and 25.0% in low, intermediate, and high pairs, respectively. RCV exceedance did not differ between <90-day and ≥ 90-day intervals (17.6% vs. 26.0%, p = 0.340). CONCLUSIONS:Most repeat measurements remained within the RCV, and clinical reclassification was uncommon. Initial Lp(a) category did not predict repeat testing behaviour, suggesting requesting decisions reflect clinical context rather than the biochemical result. These findings support selective, indication-driven repeat testing rather than routine serial monitoring.
There is a lack of resources on how to prepare, execute, and sustain quality improvement (QI) initiatives in laboratory medicine. The project goal was to bridge this gap with the creation of a novel primer series. In this third and final primer, we discuss fundamental concepts related to project evaluation, dissemination, and sustainability. We also introduce useful tools to successfully assess and monitor QI project success over time, including run charts and statistical process control charts as well as a well established sustainability model. These concepts are illustrated by following through on the final results from our real-world clinical vignette related to serum protein electrophoresis (SPEP) utilization. The impact of interventions discussed in earlier articles of the primer series was evaluated over a one-year period. Data analysis showed there was a >99% reduction in repeat SPEP testing in less than 75 days. The secondary aim to reduce testing in patients <50 years was not met. By piecing together the central aspects of QI methodology and challenges encountered from project initiation to dissemination through a laboratory lens, this series aims to support engagement of clinical laboratory leaders in QI initiatives. This is essential to build a strong culture of QI within the clinical laboratory and beyond.
OBJECTIVE:Individual analytical errors in neonatal and infant bilirubin testing may pose serious clinical risk, for example, when very small samples are incompletely aspirated without triggering analyser error flags, causing falsely low results which may mask dangerous levels. Because the routinely measured icteric index (ICT) correlates with bilirubin, we evaluated whether a total bilirubin-to-icteric index ratio (TBIL/ICT) could identify discrepantly low TBIL results. METHODS:The study comprised two phases. In the threshold-derivation phase, routinely reported TBIL results were reviewed for infants aged ≤90 days with ICT >26 from Abbott Alinity platforms across three laboratories between June 2023 and May 2024. Visual outliers in the TBIL-ICT relationship were used to derive a TBIL/ICT threshold. The derived threshold was implemented, and triggered cases were reviewed over 19 months from June 2024 to December 2025 in the post-implementation assessment phase. RESULTS:In the derivation cohort of 12,057 qualifying samples, TBIL correlated strongly with ICT (Pearson r = 0.918, p < 0.001; Passing-Bablok regression TBIL = 0.708 × ICT + 13.361). Forty-nine samples (0.41%) were classified as visual outliers. A TBIL/ICT threshold <0.54 detected all visual outliers, with 99.9% specificity and 84.5% positive predictive value (PPV) against visual outlier classification. During the post-implementation assessment, 69 (0.19%) of 35,820 eligible samples triggered the TBIL/ICT <0.54 threshold. Of these, 55 (79.7%) were classified as individual false-low TBIL errors, seven (10.1%) as genuine results, and seven were unclassifiable. PPV was 79.7% for all flagged samples, and 88.7% when excluding unclassifiable samples. CONCLUSION:A TBIL/ICT ratio < 0.54 demonstrated a good PPV in detecting false-low TBIL results in infants on the Abbott Alinity system and provided a feasible, low-burden safeguard. Platform-specific validation is required before the adoption of TBIL/ICT on other systems.
Broul and colleagues provide a timely high-value approach to laboratory testing in erectile dysfunction and suspected hypogonadism. We extend their analysis by proposing VALOR-ED, a five-component pathway that links phenotype verification, analytical fitness, cardiometabolic risk, selective reflex testing, and actionable reporting. The framework addresses assay variability, borderline biochemical results, diagnostic inequity, and the frequent disconnect between laboratory testing and preventive care. Multicentre validation across diverse laboratory platforms and health systems could establish an internationally applicable benchmark for clinically actionable and equitable testing.
OBJECTIVES:A substantial proportion of patients undergoing focused parathyroidectomy fail to meet the "≥50% intraoperative parathyroid hormone (ioPTH) drop" criterion at 10 min despite ultimately achieving biochemical cure. This study aimed to determine the frequency of delayed ioPTH decline and associated factors. DESIGN & METHODS:We conducted a retrospective cohort study including patients with primary hyperparathyroidism undergoing successful parathyroidectomy for uniglandular disease with ioPTH monitoring between 2017 and 2023. Blood samples were obtained at baseline, 5, 10, and 15-20 min after gland excision. Additional measurements beyond 20 min were collected at the surgeon's discretion. Delayed responders (DR) were defined as patients achieving a ≥ 50% ioPTH decrease from the pre-incision baseline later than 10 min. Univariable analyses and multivariable Firth-penalized logistic regression identified predictors of delayed response. RESULTS:A total of 190 patients were included. A ≥ 50% ioPTH decline was achieved at 10 min in 160/190 patients (84.2%), whereas 30/190 (15.8%) were classified as DR. Of these, 22/190 (11.6%) met the criterion at 15-20 min and 8/190 (4.2%) beyond 20 min. Half of DR exhibited a 10-min ioPTH decline within the 40.0%-49.9% range. A manipulation-induced 5-min ioPTH spike occurred exclusively among DR (44.8% vs 0%; p < 0.001). Baseline ioPTH <100 pg/mL (10.6 pmol/L) was also strongly associated with delayed biochemical decline (50.0% vs 12.2%; p = 0.0003). Both factors remained significant in multivariable analysis. CONCLUSIONS:One in six patients undergoing successful parathyroidectomy exhibited a delayed biochemical response. Low baseline ioPTH levels and manipulation-induced PTH spikes were strong independent predictors. Careful interpretation of early ioPTH kinetics and delayed sampling, particularly after a substantial but insufficient 10-min decline, may reduce unnecessary bilateral neck exploration in selected patients.
Chronic pain affects over a quarter of Canadians and remains a leading cause of outpatient visits. It is prevalent in both adults and children, often persisting into adulthood, and imposes a significant economic burden exceeding $40 billion annually. Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for pain management as a safer alternative to opioids. However, the safety and efficacy of NSAIDs are influenced by genetic factors, particularly cytochrome P450 (CYP) polymorphisms, which affect drug metabolism. The CYP2C9 enzyme metabolizes several NSAIDs, and genetic variations can lead to altered drug clearance, increasing the risk of adverse effects such as gastrointestinal bleeding. Pharmacogenomic (PGx) testing, including CYP2C9 genotyping, provides insights into individual drug response, aiding personalized pain management. Guidelines from the Clinical Pharmacogenetics Implementation Consortium (CPIC) recommend NSAID dose adjustments based on CYP2C9 genotype. Additionally, drug-gene interactions, drug-drug interactions, and phenoconversion further complicate the metabolism of NSAIDs. Phenoconversion, wherein drug-induced or disease-related changes alter an individual's metabolic phenotype independent of their genotype, can significantly impact the metabolism of NSAIDs and therapeutic outcomes, highlighting the need for dynamic clinical assessments. Integrating PGx testing into clinical practice can enhance the safety and efficacy of NSAIDs, reducing adverse effects and optimizing pain treatment. Further research is needed to explore additional genetic and environmental factors, including phenoconversion mechanisms, which influence responses to NSAIDs, paving the way for precision medicine in pain management.
BACKGROUND:Benzodiazepine immunoassays are commonly used for urine drug screening but have historically demonstrated poor detection of glucuronidated metabolites, resulting in false-negative results. A reformulated Roche benzodiazepine immunoassay (BNZ2) incorporating β-glucuronidase was developed to improve detection of glucuronidated benzodiazepines. This study evaluated the impact of BNZ2 implementation on false-positive rates in a tertiary medical center. METHODS:A retrospective observational study compared urine benzodiazepine screening results from 12 months before and after BNZ2 implementation. Screening was performed using Roche BENZ Plus or BNZ2 reagents on the Roche Cobas Pro c503 analyzer. Presumptive positive results underwent reflex confirmatory testing by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Amphetamine screening served as an internal control. RESULTS:With BENZ Plus, 363/4513 (8.0%) screens were presumptive positive, compared with 827/4665 (17.7%) following BNZ2 implementation. Confirmatory testing demonstrated false-positive rates of 1.2-1.5% with BENZ Plus and 5.9-7.8% with BNZ2 (p < 0.001). Medication review for patients with false-positive samples identified some common prescriptions but could not identify a causal agent. Amphetamine false-positive rates remained stable across periods (16.2% vs 16.3%, p > 0.05). Following BNZ2 implementation, lorazepam became the most frequently confirmed benzodiazepine (36.7%, n = 269), with substantial increases in lorazepam-only positive samples. CONCLUSIONS:BNZ2 reformulation improved detection of glucuronidated benzodiazepines, particularly lorazepam, but was associated with a significant increase in false-positive results. In this population, 1 in 8 additional presumptive positive samples on BNZ2 was a false positive. These findings demonstrate a trade-off between improved analytical sensitivity and reduced specificity, resulting in increased confirmatory testing requirements and potential downstream effects on laboratory workflow and clinical decision-making.
Introduction The discordance between cystatin C- and creatinine-based eGFR (eGFRdiff) predicts mortality in CKD, but what this index actually reflects remains unclear. We examined the relative contributions of several biomarkers, representing muscle mass, middle-molecule retention, cardiac injury, inflammation, and physical function, to the eGFRdiff-mortality association in a nationally representative US population. Materials and Methods We analyzed 1503 adults with CKD stages 1-4 from NHANES 1999-2004 with mortality follow-up through 2019. The exposure was percentage eGFRdiff. Survey-weighted Cox models estimated HRs for mortality. Attenuation analyses quantified the contribution of each candidate biomarker. Residualization analyses decomposed the B2M signal by adjusting for creatinine-based, cystatin C-based, and combined eGFR estimates separately. Results 911 all-cause and 313 cardiovascular deaths occurred. Each 1-SD more negative eGFRdiff was associated with higher all-cause (HR 1.29; 95%CI 1.15-1.46) and cardiovascular mortality (HR 1.46; 95%CI 1.23-1.72). DXA-derived muscle mass yielded negligible attenuation (1.3%), and physical limitation produced modest attenuation (11.2%). In contrast, B2M produced the largest attenuation (73.4%), followed by hs-cTnT (32.0%) and NT-proBNP (23.0%). Residualization on eGFRcr preserved the B2M attenuation (80.1%), whereas residualization on eGFRcys abolished it (-7.9%). B2M residualized on eGFRcr-cys retained 21.9% attenuation. Conclusions Middle-molecule retention (represented by B2M), not muscle mass, is the primary contributor to the prognostic value of eGFRdiff, with cardiac biomarkers contributing secondarily. Residualization patterns support a biological signal consistent with shrunken pore syndrome rather than a mathematical artifact of how eGFR is estimated. Calculable from routine assays, eGFRdiff may offer a practical indicator of middle-molecule burden and cardiac stress for CKD risk stratification.
INTRODUCTION:Accurate interpretation of plasma renin concentration (PRC) and plasma aldosterone concentration (PAC) requires population-specific reference intervals, which remain scarce in Southeast Asian populations. Manufacturer-derived reference intervals are based predominantly on Western cohorts and may not be directly applicable to regional populations. MATERIALS AND METHODS:This cross-sectional study recruited 300 healthy, normotensive, non-obese adults (149 males, 151 females; mean age 34.4 ± 10.7 years) from a multi-ethnic Malaysian cohort in Sarawak to establish reference intervals for PAC and PRC. Strict exclusion criteria were applied to minimize confounding from medications, smoking, obesity, renal dysfunction, and hypokalemia. PAC and PRC were measured under standardized seated morning conditions using the DiaSorin Liaison® XL chemiluminescent immunoassay (CLIA). Reference intervals were derived using the IFCC-recommended non-parametric method, with sex- and age-stratified analyses. RESULTS:The reference intervals were 2.13-30.1 ng/dL (2.5th to 97.5th percentile) for PAC (range 1.25-42.30 ng/dL) and 7.4-66.4 μIU/mL (5th to 95th percentile) for PRC (range 1.31-107.80 μIU/mL). Participants aged ≥40 years had significantly lower PAC and PRC than younger participants. On multivariable regression analysis, PAC was independently associated with serum potassium and estimated 24-h urine sodium excretion, whereas PRC was independently associated with age, sex, systolic blood pressure, and estimated 24-h urinary sodium excretion. No significant difference in PAC and PRC was observed across ethnic groups. CONCLUSIONS:We report the first platform-specific, sex- and age-stratified reference intervals for PAC and PRC in a healthy Southeast Asian population using the DiaSorin Liaison® XL CLIA platform. The derived intervals differed from manufacturer-provided values, highlighting the importance of locally validated reference data for accurate interpretation of RAAS biomarkers and clinical evaluation of endocrine and hypertensive disorders.
BACKGROUND:In clinical laboratory practice, reference intervals (RIs) for chemistry analytes are commonly adopted directly from manufacturer package inserts. These intervals are typically verified locally according to regulatory requirements rather than independently derived, under the assumption that manufacturer-reported RIs are broadly applicable across patient populations. In low pre-test probability settings such as routine outpatient testing or wellness testing, this approach can generate a high frequency of flagged abnormalities that more likely reflects biological variation rather than disease. Expanding RIs to the central 99% has been proposed as a strategy to improve specificity. METHODS:The 99% RIs were derived for CMP analytes using retrospective data from 23,422 unique adult outpatients tested at a single institution in September 2025. Results were compared with 95% RIs and manufacturer-provided RIs across analytes. Flagging performance was evaluated using an independent retrospective dataset of 28,006 adult outpatients tested between December 2025 and January 2026. Analyses focused on the proportion of results flagged outside each RI. RESULTS:Electrolytes, including sodium, chloride, calcium, and CO₂, showed minimal differences in flagging between manufacturer RIs and 99%-derived intervals, with differences consistently under 7%. In contrast, kidney and liver analytes demonstrated substantial variability. Manufacturer RIs flagged a markedly higher proportion of results outside the interval for creatinine, AST, ALT, ALP, BUN, potassium, and total protein compared with the 99% approach. CONCLUSIONS:Electrolyte RIs are consistent across manufacturer-provided RIs and population-derived 99% intervals. In contrast, kidney and liver analytes show pronounced differences between historical package insert RIs and contemporary percentile-based distributions, resulting in substantial variation in abnormal result flagging. These findings highlight the impact of using alternate approaches to derive our kidney and liver RIs.
INTRODUCTION:We compared analytical outlier rates for cardiac troponin T (cTnT) between biotin sensitive and insensitive testing reagents, and between testing platforms Roche Cobas e411 and e601. METHODS:Plasma samples from hospitalized patients were tested on a Roche Cobas e411 analyzer using lots of Roche Elecsys Troponin T Gen 5 Stat reagent labelled free of biotin interference at ≤20 ng/mL (biotin sensitive reagent, n = 1997); compared to samples tested on a Roche Cobas e601 analyzer using the same reagent labelled free from biotin interference at ≤1200 ng/mL (biotin insensitive, n = 2555). Samples with measurable cTnT (≥6 ng/L) were aliquoted, re-centrifuged and retested on the same analyzer. Analytical outliers were defined as repeat value that differed from the initial value by a critical difference (CD): where CD = z x 2 x SDanalytical, with a z-value of 3.719. RESULTS:The total number of outliers that were observed for the biotin-sensitive reagent on the e411 was 68/1997 (3.4%), compared to 208/2555 (8.1%) on the biotin-insensitive reagent measured on the e601 (p < 0.0001). Outliers were observed in 45 (2.6%) of samples with initial values <100 ng/L using the biotin-sensitive reagent compared to 138 (6.4%) of samples using biotin insensitive (p < 0.0001). Among these samples, outliers with repeat values differing by ≥10 ng/L occurred for 0.8% and 1.3% of samples tested with the biotin sensitive and insensitive reagent, respectively. CONCLUSIONS:cTnT analytical outliers occurred more than twice as often using biotin-insensitive reagent on the Cobas e601 analyzer compared to biotin-sensitive reagent on the Cobas e411.
INTRODUCTION:Chemical urinalysis provides rapid analysis of multiple tests simultaneously including glucose, ketones, leukocyte esterase, nitrite, bilirubin, urobilinogen, pH, specific gravity, protein and hemoglobin. While highly coloured urines may impact readability of urine dipsticks there is no specific data on the effects of visible blood for dipstick analysis. We aimed to evaluate the effect of urinary hemoglobin on 10SG multistix and establish a process for handling visibly bloody urines received in our laboratories. METHODS:In vitro bloody urine pools were made using residual RBCs or leukoreduced RBCs and tested for interference patterns among tests included on the 10SG multistix. We further examined the effect of centrifugation and lysis on bloody urine samples both in vitro and among visibly bloody patient urine specimens. RESULTS:The presence of blood in urine samples caused profound interference for leukocyte esterase, nitrite, protein, glucose, ketones, and urobilinogen. Urine protein was most sensitive to hemoglobin interference at >0.2 g Hgb/L; and clinically significant interference was observed at >1 g Hgb/L with 10SG dipsticks. Bloody patient urines demonstrated similar interference patterns observed in vitro, although some clinical samples were positive for bilirubin. This phenomenon was replicated in vitro after RBC lysis. Centrifugation was not a viable strategy to eliminate interference due to blood. CONCLUSION:Visibly bloody urines are wholly unreliable for chemical urinalysis with 10SG multistix when hemoglobin is >1 g/L. An optimal process was established to withhold results of visibly bloody urines when dipstick hemoglobin is 3+ and protein is >1+ using 10SG multistix.
BACKGROUND:Point-of-care (POC) glucose meters are widely used in intensive care units (ICUs) for rapid glucose monitoring. However, their accuracy may be affected by pathological and physiological factors in different critically ill patients. METHODS:Dataset 1 consisted of a three-year quality assurance (QA) practice (2022-2024) using non-ICU samples. Dataset 2 included paired glucose results from patients in general ICU, cardiac ICU, and neonatal ICU collected over six months (July to December 2024), with measurements obtained within a 20-min interval. Agreement of results between glucose meters and blood gas analyzers (BGAs) was assessed using Deming regression, ISO 15197:2013 criteria, and the Diabetes Technology Society (DTS) Error Grid. RESULTS:In the QA dataset (n = 1476), glucose meter results showed excellent correlation with BGAs (r = 0.9930), with 92.6% (<5.0 mmol/L) and 88.2% (≥5.0 mmol/L) of results meeting ISO criteria. In ICU patients (n = 985), correlation was significantly lower (r = 0.8509), with slightly reduced agreement at higher glucose concentrations (82.5%). Performance varied across ICU populations, with the lowest correlation observed in the general ICU (r = 0.8068). Agreement at critically high glucose levels was markedly reduced in clinical settings compared with QA data (43.2% vs. 74.2%). DTS Error Grid analysis showed that 1.23% of the differences between glucose meters and BGAs fell within moderate- or high-risk zones. CONCLUSIONS:The analytical accuracy of POC glucose meters is significantly reduced in ICU settings and varies among patient populations. Meter performance evaluation should be conducted under real clinical conditions, with particular attention to extreme glucose levels. The performance data should be shared with ICU physicians to support appropriate interpretation of glucose results.
