Imprecision of high-sensitivity cardiac troponin assays at the female 99th-percentile.

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 CVpooled = 6.3 % and Beckman CVpooled = 7.0 %). One of four Siemens Atellica instruments yielded a CV > 10.0 % (CVpooled = 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) (CVpooled = 11.7 %). Four Roche instruments also yielded CVs > 10.0 % near the female URL of 14 ng/L used in the United States (CVpooled = 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.

Age-Stratified Lithium Therapeutic Ranges for Older Adults with Bipolar Disorder - from Awareness to an Action Plan.

Lithium is the first-line treatment for maintenance therapy in bipolar disorder. It is an effective mood stabilizer agent, and may have potential benefits in neuroprotection and reducing the risk of suicide. Toxicity has been a concern in recent decades, particularly in older adults (≥60 years). In 2019, the Older Adults Task Force within the International Society for Bipolar Disorder (ISBD) published recommendations for age-stratified lithium therapeutic ranges for therapy of Older Age Bipolar Disorder (OABD), namely 0.4 - 0.8 mmol/L for ages 60 to 79 and 0.4 - 0.7 mmol/L for ages 80 and above. Clinical laboratory practice surveys in Canada indicated that adoption and implementation of the proposed ranges has been limited to date. In this article, we describe the approach and steps taken to evaluate and implement recommended lithium therapeutic ranges in Ontario and other provinces in Canada for laboratory quality improvement. Sources of variation in lithium reporting practices are discussed and shared here to highlight potential barriers to implementation. The overall goal of this article is to bring attention across the global laboratory community that lower lithium therapeutic target ranges in older patients are crucial for patient safety in OABD.

Establishing quality indicators for point of care glucose testing: recommendations from the Canadian Society for Clinical Chemists Point of Care Testing and Quality Indicators Special Interest Groups.

OBJECTIVES: Monitoring quality indicators (QIs) is an important part of laboratory quality assurance (QA). Here, the Canadian Society of Clinical Chemists (CSCC) Point of Care Testing (POCT) and QI Special Interest Groups describe a process for establishing and monitoring QIs for POCT glucose testing. METHODS: Key, error prone steps in the POCT glucose testing process were collaboratively mapped out, followed by risk assessment for each step. Steps with the highest risk and ability to detect a non-conformance were chosen for follow-up. These were positive patient identification (PPID) and repeat of critically high glucose measurements. Participating sites were asked to submit aggregate data for these indicators from their site(s) for a one-month period. The PPID QI was also included as part of a national QI monitoring program for which fifty-seven sites submitted data. RESULTS: The percentage of POCT glucose tests performed without valid PPID ranged from 0-87%. Sites without Admission-Discharge-Transfer (ADT) connectivity to POCT meters were among those with the highest percentage of POCT glucose tests performed without valid PPID. The percentage repeated critically high glucose measurements ranged from 0-50%, indicating low compliance with this recommendation. A high rate of discordance was also noted when critically high POCT glucose measurements were repeated, demonstrating the importance of repeat testing prior to insulin administration. CONCLUSIONS: Here, a process for establishing these QIs is described, with preliminary data for two QIs chosen from this process. The findings demonstrate the importance of QIs for identification and comparative performance monitoring of non-conformances to improve POCT quality.

Vitamin D Toxicity from an Unusual and Unexpected Source: A Report of 2 Cases.

INTRODUCTION: Hypervitaminosis D is a relatively uncommon etiology of hypercalcemia. Toxicity is usually caused by very high doses, mostly secondary to erroneous prescription or administration of vitamin D, and less commonly, contaminated foods or manufacturing errors of vitamin D-containing supplements. CASE PRESENTATION: A 16-year-old male, previously healthy, presented with 2-week history of nonspecific symptoms (fatigue, gastrointestinal complaints). Investigations showed acute kidney injury and hypercalcemia (total calcium 3.81 mmol/L). Further diagnostic workup revealed markedly elevated 25-hydroxyvitamin D levels (1,910 nmol/L). He denied taking any vitamin D supplements; however, he reported consumption of creatine and protein supplements. Mass spectrometry analysis of the creatine supplement estimated a vitamin D content of 425,000 IU per serving (100 times the upper tolerable daily dose). A few months later, another previously healthy adolescent presented with severe hypercalcemia and acute kidney injury secondary to hypervitaminosis D. He was also using a creatine supplement, from the same manufacturer brand and lot. Both patients were treated with intravenous hydration, calcitonin, and pamidronate. They maintained normocalcemia after their initial presentation but required low-calcium diets and laboratory testing for months after this exposure. DISCUSSION/CONCLUSION: We present 2 cases of hypervitaminosis D caused by a manufacturing error of a natural health product which did not claim to contain vitamin D. The use of dietary supplements is highly prevalent; this should be incorporated while taking medical history, and considered a potential source of toxicity when an alternative source cannot be found, regardless of the product label.

Rapid COVID-19 testing: Speed, quality and cost. Can you have all three?

KEY MESSAGES.

Quality assurance practices for point of care testing programs: Recommendations by the Canadian society of clinical chemists point of care testing interest group.

Point of Care Testing (POCT) refers to clinical laboratory testing performed outside the central laboratory, nearer to the patient and sometimes at the patient bedside. The testing is usually performed by clinical staff, such as physicians or nurses, who are not laboratory trained. This document was developed by the POCT Interest group of the Canadian Society of Clinical Chemists (CSCC) as practical guidance for quality assurance practices related to POCT performed in hospital and outside hospital environments. The aspects of quality assurance addressed in this document include: (1) device selection, (2) initial device verification, (3) ongoing device verification, (4) ongoing quality assurance including reagent and quality control (QC) lot changes, and (5) quality management including operator and document management.

Performance of StatSensor Point-of-Care Device for Measuring Creatinine in Patients With Chronic Kidney Disease and Postkidney Transplantation.

BACKGROUND: The StatSensor is a point-of-care device which measures creatinine in capillary whole blood. Previous studies reported an underestimation of the creatinine measurements at high creatinine concentrations and were performed in the prestandardization era for creatinine. OBJECTIVE: This accuracy-based study evaluates the use of this device in kidney-transplanted patients and those with chronic kidney disease (CKD). DESIGN: Cross-sectional diagnostic accuracy study. SETTING: Nephrology outpatient clinic in an urban tertiary center. PARTICIPANTS: Adults with CKD or a functioning kidney transplant. MEASUREMENTS: Duplicate StatSensor creatinine measurements were performed on capillary whole blood samples collected by direct fingerstick and SAFE-T-FILL collection device. Results were compared with simultaneous venous blood sampling for serum and plasma creatinine measured by an enzymatic method on the Roche Integra 400 mainframe analyzer with traceability to the ID-GC-MS (isotope dilution gas chromatography mass spectrometry) reference method. METHODS: Deming regression, Pearson correlation coefficient, and Bland-Altman analysis were used to assess accuracy and comparability between capillary whole blood measured by StatSensor and plasma creatinine measured by routine analyzer with traceability to the reference method. Estimated glomerular filtration (eGFR) rates were calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and concordance with Kidney Disease Improving Global Outcomes (KDIGO) CKD stage classification was evaluated. RESULTS: There were 60 participants (mean age = 61.9 ± 15.0 years, 55% men, 33% transplant, mean plasma creatinine = 137 ± 59 µmol/L). Bland-Altman analysis indicated a positive mean bias of 12.7 µmol/L between StatSensor fingerstick creatinine measurement and plasma creatinine. Comparison of eGFR (CKD-EPI) calculated from the StatSensor fingerstick creatinine versus plasma creatinine showed misclassification across all KDIGO CKD stages. Postanalytical correction of the bias did not improve misclassifications. The use of mean of duplicate StatSensor creatinine results did not improve performance compared with the use of singlet results. LIMITATIONS: Single center, limited participant numbers. CONCLUSIONS: The results of our study suggest that the limiting characteristics of the StatSensor device are not only bias, but also imprecision. The level of imprecision observed may influence clinical decision-making and limit the usefulness of StatSensor as a CKD screening tool. If choosing to utilize it for either screening for or monitoring CKD, it is essential that clinicians understand the limitations of point-of-care devices and apply this knowledge to test interpretation.

CONTEXTE: Le StatSensor est un appareil portatif conçu pour mesurer le taux de créatinine dans le sang capillaire total. Des études antérieures, réalisées avant la standardisation des mesures de la créatinine, ont rapporté une sous-estimation des mesures à des concentrations élevées. OBJECTIF: Cette étude centrée sur la précision a examiné l'utilisation de cet appareil chez des patients transplantés d'un rein et des patients atteints d'insuffisance rénale chronique (IRC). TYPE D'ÉTUDE: Étude transversale centrée sur la précision du diagnostic. CADRE: La clinique ambulatoire de néphrologie d'un centre de soins tertiaires en milieu urbain. SUJETS: Des adultes atteints d'IRC ou transplantés avec un rein fonctionnel. MESURES: Les mesures de créatinine par StatSensor ont été effectuées en double sur des échantillons de sang capillaire total prélevés par ponction digitale directe et à l'aide du dispositif de prélèvement SAFE-T-FILL. Ces résultats ont été comparés à un prélèvement veineux simultané pour la mesure des taux de créatinine sérique et plasmatique par la méthode enzymatique avec l'analyseur Integra 400 de Roche avec traçabilité à la méthode de référence ID-GC-MS. MÉTHODOLOGIE: La régression de Deming, le coefficient de corrélation de Pearson et l'analyse de Bland-Altman ont été utilisés pour évaluer la précision et la comparabilité entre les mesures du sang capillaire total par StatSensor et la mesure de créatinine plasmatique obtenue par l'analyseur de routine avec traçabilité à la méthode de référence. Le débit de filtration glomérulaire estimé (DFGe) a été calculé avec l'équation CKD-EPI, puis la concordance avec la classification des stades KDIGO pour l'IRC a été évaluée. RÉSULTATS: L'étude a inclus 60 patients (55 % d'hommes; âge moyen 61,9 ± 15,0 ans) dont 33 % étaient transplantés. Le taux moyen de créatinine plasmatique s'établissait à 137 ± 59 µmol/L. L'analyse de Bland-Altman indique un biais positif moyen de 12,7 µmol/L entre la mesure de créatinine obtenue avec StatSensor par ponction digitale et le taux de créatinine plasmatique. La comparaison entre le DFGe (CKD-EPI) calculé à partir des mesures obtenues par ponction digitale avec StatSensor et de la mesure de créatinine plasmatique a montré une classification erronée à tous les stades KDIGO pour l'IRC. La correction du biais après l'analyse n'a pas amélioré les erreurs de classification. L'utilisation de la moyenne des résultats obtenus par StatSensor sur les échantillons prélevés en double n'a pas amélioré les performances par rapport à l'utilisation de singulets. LIMITES: Étude monocentrique, nombre de participants limité. CONCLUSION: Nos résultats suggèrent que les caractéristiques de limitation du StatSensor ne constituent pas qu'un biais, mais également une imprécision. Ce degré d'imprécision peut influencer la prise de décision clinique et limiter l'utilité du StatSensor comme outil de dépistage de l'IRC. Il est essentiel que les cliniciens soient conscients des limites de ces dispositifs et qu'ils appliquent ces connaissances à l'interprétation des résultats s'ils choisissent de les utiliser pour dépister ou surveiller l'IRC. ENREGISTREMENT DE L'ESSAI: Sans objet, il ne s'agissait pas d'un essai clinique.

Utilizing connectivity and data management system for effective quality management and regulatory compliance in point of care testing.

Point of care testing (POCT) is one of the fastest growing disciplines in clinical laboratory medicine. POCT devices are widely used in both acute and chronic patient management in the hospital and primary physician office settings. As demands for POCT in various healthcare settings increase, managing the quality and regulatory compliance are continually challenging. Despite technological advances in applying automatic system checks and built-in quality control to prevent analytical and operator errors, poor planning for POCT connectivity and informatics can limit data accessibility and management efficiency which impedes the utilization of POCT to its full potential. This article will summarize how connectivity and data management system can improve timely access to POCT results, effective management of POCT programs, and ensure regulatory compliance.

IgG4 plasma cell myeloma without clinical evidence of IgG4-related disease: a report of two cases.

Background: Serum IgG4 is typically measured to investigate for Immunoglobulin G4-related Disease (IgG4-RD), a fibroinflammatory condition associated with polyclonal increase in serum IgG4. However, increased IgG4 can also be monoclonal, and little is known about IgG4 myeloma. Methods: We describe two cases of IgG4 myeloma without clinical, radiologic, or laboratory features of IgG4-related disease. Results: An 84 year old man presented with anemia and compression fractures and a 77 year old man presented with anemia, hypercalcemia and renal failure. Both had markedly elevated monoclonal serum IgG4, 34 g/L and 48 g/L in the beta region, and increased IgG positive bone marrow plasma cells, 50% and 80%, respectively. Neither had clinical or radiological manifestations of IgG4-related disease (IgG4-RD) such as salivary or lacrimal gland swelling, autoimmune pancreatitis , or retroperitoneal fibrosis. Both cases responded well to standard myeloma therapy. The IgG4 paraprotein caused spuriously elevated beta-2 microglobulin of 45.2 mg/L in case two due to interference with the assay. Conclusion: These cases illustrate the importance of performing serum protein electrophoresis in tandem with IgG subclasses to distinguish between polyclonal and monoclonal increases in serum IgG4. The lack of typical IgG4-RD features in these two patients suggests that monoclonal elevation in serum IgG4 alone is insufficient to cause the organ damage characteristic of IgG4-RD. Larger studies of IgG myeloma subtypes are warranted to explore whether IgG1, IgG2, IgG3 and IgG4 myeloma differ in natural history and whether the interference with beta-2 microglobulin is specific to IgG4 monoclonal proteins.

Clinical utility of serum IgG4 measurement.

This article will review the structure and function of IgG4, methods of measuring serum IgG4 concentrations, clinical conditions associated with increased and decreased serum IgG4, and the test characteristics of serum IgG4 in the diagnosis and management of Immunoglobulin G4-Related Disease (IgG4-RD). The four subclasses of IgG were discovered in 1964 through experiments on monoclonal IgG in patients with myeloma. Since 2001, interest in measuring serum IgG subclasses has increased dramatically due to the emergence of IgG4-RD, a multisystem fibroinflammatory condition wherein polyclonal serum IgG4 concentration is increased in approximately 70% of cases. Increased serum IgG4 typically manifests as a restriction in the anodal gamma region on serum protein electrophoresis, often with beta-gamma bridging, and can be mistaken as a monoclonal protein or polyclonal increase in IgA. Limitations of current clinical methods used in quantitation of serum IgG4 concentrations will be discussed, including the common immunonephelometric assays and LC-MS/MS based assays. Polyclonal IgG4 elevation is not specific for IgG4-RD, and may also occur in conditions such as eosinophilic granulomatosis with polyangiitis (EGPA), lymphoma, and multicentric Castleman disease (MCD). Race and gender differences also affect interpretation of serum IgG4 concentrations, for instance Asians have a higher serum IgG4 concentration than Whites and males have a higher concentration than females.

Emerging role of clinical mass spectrometry in pathology.

Mass spectrometry-based assays have been increasingly implemented in various disciplines in clinical diagnostic laboratories for their combined advantages in multiplexing capacity and high analytical specificity and sensitivity. It is now routinely used in areas including reference methods development, therapeutic drug monitoring, toxicology, endocrinology, paediatrics, immunology and microbiology to identify and quantify biomolecules in a variety of biological specimens. As new ionisation methods, instrumentation and techniques are continuously being improved and developed, novel mass spectrometry-based clinical applications will emerge for areas such as proteomics, metabolomics, haematology and anatomical pathology. This review will summarise the general principles of mass spectrometry and specifically highlight current and future clinical applications in anatomical pathology.

Pediatric reference intervals for 1,25-dihydroxyvitamin D using the DiaSorin LIAISON XL assay in the healthy CALIPER cohort.

BACKGROUND: 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active vitamin D metabolite, plays a critical role in calcium and phosphate homeostasis. 1,25(OH)2D is measured to assess calcium and phosphate metabolism, particularly during periods of profound growth and development. Despite its importance, no reliable pediatric reference interval exists, with those available developed using adult populations or out-dated methodologies. Using the fully automated chemiluminescence immunoassay by DiaSorin, we established 1,25(OH)2D pediatric reference intervals using healthy children and adolescents from the CALIPER cohort. METHODS: Serum samples from healthy subjects (0 to <19 years) were analyzed for 1,25(OH)2D using the DiaSorin LIAISON XL assay and age-specific reference intervals were established. The Mann-Whitney U-test was used to determine seasonal differences. Pooled neonatal and infantile samples were quantified using liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine if elevated concentrations during the first year of life may be attributed to cross-reacting moieties. RESULTS: Three reference interval age partitions were required with highest levels in subjects 0 to <1 year (77-471 pmol/L), which declined and narrowed after 1 year (113-363 pmol/L) and plateaued at 3 years (108-246 pmol/L). 1,25(OH)2D concentration was not significantly affected by seasonal variation or sex. Elevated 1,25(OH)2D concentrations in neonatal and infantile samples may be the result of an interfering substance. The absence of 3-epi-1,25-dihydroxyvitamin D in the pooled samples makes it unlikely to be the interfering moiety. CONCLUSIONS: Pediatric reference intervals for 1,25(OH)2D were established to improve test result interpretation in children and adolescents. 1,25(OH)2D is elevated in a proportion of neonates and infants, which may be the result of a cross-reacting moiety.

Pediatric reference intervals for 29 Ortho VITROS 5600 immunoassays using the CALIPER cohort of healthy children and adolescents.

BACKGROUND: Accurate reference intervals (RIs) based on a healthy pediatric population are essential for pediatric test result interpretation. The CALIPER project has recruited a large healthy cohort and completed a series of a priori studies to address gaps in pediatric RIs. As immunoassays from different manufacturers for endocrine and special chemistry markers are not standardized and show marked intermethod differences, direct RI studies are needed for each major analytical platform. Here, we report age- and sex-specific pediatric RIs for 29 immunoassays on the Ortho Clinical Diagnostics (Ortho) VITROS® 5600 analyzer. METHODS: Health information and blood samples were collected from healthy pediatric subjects. Using the Ortho VITROS 5600 Integrated System MicroWell Technology, 29 biomarkers were measured. Analyte concentrations were partitioned by age and sex according to the Harris and Boyd method. After removing outliers, age- and sex-specific RIs and corresponding 90% confidence intervals were calculated according to CLSI guidelines. RESULTS: All analytes required age partitioning except ß-human chorionic gonadotropin (ß-hCG), cancer antigen 15-3 (CA15-3), rubella immunoglobulin G (rubella IgG), and vitamin D. Several analytes including estradiol, progesterone, testosterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), free triiodothyronine (FT3), total triiodothyronine (TT3), total thyroxine (TT4), thyroid uptake, ferritin, intact parathyroid hormone (iPTH), total prostate-specific antigen (tPSA), free prostate-specific antigen (fPSA), cancer antigen 125 (CA125), creatine kinase MB (CK-MB), and myoglobin showed sex differences, observed mostly with the onset of puberty. CONCLUSIONS: Complex reference value trends were observed across the pediatric age range for several biomarkers examined on Ortho VITROS immunoassays. The availability of VITROS immunoassay RIs will enable accurate laboratory test interpretation and diagnosis for the pediatric population. As recommended by the CLSI EP28-A3c guidelines, implementation of these RIs should be validated for each laboratory's local pediatric population.

Evaluation of electrochemiluminescence immunoassays for immunosuppressive drugs on the Roche cobas e411 analyzer.

Background:  Therapeutic drug monitoring of immunosuppressant drugs are used to monitor drug efficacy and toxicity and to prevent organ transplant rejection. This study evaluates the analytical performance of semi-automated electrochemiluminescence immunoassays (ECLIA) for cyclosporine (CSA), tacrolimus (TAC) and sirolimus (SRL) on the Roche cobas e 411 analyzer at a major transplant hospital to assess method suitability and limitations. Methods: Residual whole blood samples from patients undergoing immunosuppressant therapy were used for evaluation. Imprecision, linearity, functional sensitivity, method comparisons and lot-to-lot comparisons were assessed. Results: Total imprecision ranged from 3.3 to 7.1% for CSA, 3.9 to 9.4% for TAC, and 4.6 to 8.2% for SRL. Linearity was verified from 30.0 to 960.9 µg/L for CSA, from 1.1 to 27.1 µg/L for TAC, and from 0.5 to 32.3 µg/L for SRL. The functional sensitivity met the manufacturer's claims and was determined to be <6.5 µg/L for CSA, 1.1 µg/L for TAC, and <0.1 µg/L for SRL (CV≤20%). Deming regression analysis of method comparisons with the ARCHITECT immunoassay yielded slopes of 0.917 (95%CI: 0.885-0.949) and r of 0.985 for CSA, 0.938 (95%CI: 0.895-0.981) and r of 0.974 for TAC, and 0.842 (0.810-1.110) and r of 0.982 for SRL. Deming regression analysis of comparisons with the LC-MS/MS method yielded slopes of 1.331 (95%CI: 1.167-1.496) and r of 0.969 for CSA, 0.924 (95%CI: 0.843-1.005) and r of 0.984 for TAC, and 0.971 (95%CI: 0.913-1.030) and r of 0.993 for SRL. Conclusions: The cobas e 411 ECLIA for CSA, TAC, and SRL have acceptable precision, linearity, and functional sensitivity. The method comparisons correlated well with the ARCHITECT immunoassay and LC-MS/MS and is fit for therapeutic drug monitoring.