Global FT4 immunoassay standardization: an expert opinion review.

OBJECTIVES: Results can vary between different free thyroxine (FT4) assays; global standardization would improve comparability of results between laboratories, allowing development of common clinical decision limits in evidence-based guidelines. CONTENT: We summarize the path to standardization of FT4 assays, and challenges associated with FT4 testing in special populations, including the need for collaborative efforts toward establishing population-specific reference intervals. The International Federation of Clinical Chemistry and Laboratory Medicine Committee for Standardization of Thyroid Function Tests has undertaken FT4 immunoassay method comparison and recalibration studies and developed a reference measurement procedure that is currently being validated. Further studies are needed to establish common reference intervals/clinical decision limits. Standardization of FT4 assays will change test results substantially; therefore, a major education program will be required to ensure stakeholders are aware of the benefits of FT4 standardization, planned transition procedure, and potential clinical impact of the changes. Assay recalibration by manufacturers and approval process simplification by regulatory authorities will help minimize the clinical impact of standardization. SUMMARY: Significant progress has been made toward standardization of FT4 testing, but technical and logistical challenges remain. OUTLOOK: Collaborative efforts by manufacturers, laboratories, and clinicians are required to achieve successful global standardization of the FT4 assays.

Clinical risk assessment of biotin interference with a high-sensitivity cardiac troponin T assay.

Objectives Biotin >20.0 ng/mL (81.8 nmol/L) can reduce Elecsys® Troponin T Gen 5 (TnT Gen 5; Roche Diagnostics) assay recovery, potentially leading to false-negative results in patients with suspected acute myocardial infarction (AMI). We aimed to determine the prevalence of elevated biotin and AMI misclassification risk from biotin interference with the TnT Gen 5 assay. Methods Biotin was measured using an Elecsys assay in two cohorts: (i) 797 0-h and 646 3-h samples from 850 US emergency department patients with suspected acute coronary syndrome (ACS); (ii) 2023 random samples from a US laboratory network, in which biotin distributions were extrapolated for higher values using pharmacokinetic modeling. Biotin >20.0 ng/mL (81.8 nmol/L) prevalence and biotin 99th percentile values were calculated. AMI misclassification risk due to biotin interference with the TnT Gen 5 assay was modeled using different assay cutoffs and test timepoints. Results ACS cohort: 1/797 (0.13%) 0-h and 1/646 (0.15%) 3-h samples had biotin >20.0 ng/mL (81.8 nmol/L); 99th percentile biotin was 2.62 ng/mL (10.7 nmol/L; 0-h) and 2.38 ng/mL (9.74 nmol/L; 3-h). Using conservative assumptions, the likelihood of false-negative AMI prediction due to biotin interference was 0.026% (0-h result; 19 ng/L TnT Gen 5 assay cutoff). US laboratory cohort: 15/2023 (0.74%) samples had biotin >20.0 ng/mL (81.8 nmol/L); 99th percentile biotin was 16.6 ng/mL (68.0 nmol/L). Misclassification risk due to biotin interference (19 ng/L TnT Gen 5 assay cutoff) was 0.025% (0-h), 0.0064% (1-h), 0.00048% (3-h), and <0.00001% (6-h). Conclusions Biotin interference has minimal impact on the TnT Gen 5 assay's clinical utility, and the likelihood of false-negative AMI prediction is extremely low.

An Evaluation of the Automated Cobas u 701 Microscopy Analyzer for the Routine Screening of Urine to Identify Negative Samples.

BACKGROUND: Urinalysis based on microbiological culture and manual microscopy requires expertise and is labor intensive. Automated screening could save time and improve patient management in clinical settings. METHODS: We evaluated the fully automated cobas u 701 analyzer for identifying infection-negative urine samples using 2,046 anonymized samples from a routine pathology laboratory. Samples containing ≥ 40 white blood cells (WBC)/µL and/or ≥ 100 bacteria/µL were considered positive. For microbiological cultures: pure growth of ≥ 108 colony-forming units (cfu)/L was considered significant; > 107 cfu/L was considered significant for pregnant women, children < 12 years, immune-compromised/critical care patients or patients with > 100 WBC/µL. RESULTS: The cobas u 701 analyzer identified 1,346 positive samples, giving a 65.7% culture rate. Sensitivity and negative predictive value were high (> 99%). Most replicates were within two standard deviations of the original measurement. CONCLUSIONS: The cobas u 701 analyzer is an effective screening tool for routine urinalysis and demonstrates rapid turnaround times, thus benefiting patients and clinicians.

The prevalence of elevated biotin in patient cohorts presenting for routine endocrinology, sepsis, and infectious disease testing.

Elevated blood biotin levels may interfere with some biotin-streptavidin immunoassays, used in clinical laboratories to aid diagnosis. The objective of this study was to determine the prevalence of elevated blood biotin levels in three at risk patient cohorts, where misclassification of disease status would have a high clinical impact. This retrospective, single-center study screened residual, de-identified plasma samples (N = 700) from adult patients undergoing routine thyroid stimulating hormone (TSH) (n = 500), procalcitonin (PCT) (n = 100), or human immunodeficiency virus (HIV) (n = 100) testing using the Elecsys® BRAHMS PCT (Roche Diagnostics), Access TSH (3rd IS) (Beckman Coulter Inc), and ARCHITECT HIV Ag/Ab Combo (Abbott Laboratories) immunoassays, respectively, for elevated levels of biotin (quantified by gas chromatography-time of flight mass spectrometry). Patients taking biotin supplements were included and dosages recorded from medical records. In the overall study cohort, blood biotin levels ranged 0.1-21.3 ng/mL; 44.3% (310/700) of samples were < 1 ng/mL, 54.7% (383/700) were 1-<10 ng/mL, and 1% (7/700) were ≥ 10 ng/mL. The sub-cohorts had similar ranges of biotin levels: 0.5-21.3 ng/mL (TSH), 0.1-12.1 ng/mL (PCT), and 0.3-7.3 ng/mL (HIV). In the 44 patients (6.3% of overall study cohort) who were documented as taking biotin supplements (range of doses, 2.5-10 mg/day), blood biotin levels ranged 0.9-21.3 ng/mL; 2.3% (1/44) of samples were < 1 ng/mL, 86.4% (38/44) were 1-<10 ng/mL, and 11.4% (5/44) were ≥ 10 ng/mL. Most patients who reported taking biotin supplements had blood biotin levels ≥ 1 ng/mL and the highest blood biotin level detected was 21.3 ng/mL.

Real-world clinical performance of commercial SARS-CoV-2 rapid antigen tests in suspected COVID-19: A systematic meta-analysis of available data as of November 20, 2020.

OBJECTIVES: Rapid antigen tests, or RATs, are a type of lateral flow chromatographic immunoassay utilized to aid the diagnosis of SARS-CoV-2 infection. We performed a systematic meta-analysis to compare the real-world performance of commercially available RATs. METHODS: We searched several databases and websites for manufacturer-independent prospective clinical performance studies comparing SARS-CoV-2 RATs and RT-PCR. Only studies on RATs that did not need a separate reader for result retrieval and that reported data on viral load, patients' symptom status, sample type, and PCR assay used were included. RESULTS: 19 studies utilizing 11,109 samples with 2,509 RT-PCR-positives were included. RAT sensitivity varied between 28.9% (95% CI 16.4-44.3) and 98.3% (95% CI 91.1-99.7), likely dependent upon population characteristics, viral load, and symptom status. RAT specificity varied between 92.4% (95% CI 87.4-95.9) and 100% (95% CI 99.7-100) with one outlier. The RATs by Roche Diagnostics/SD Biosensor and Abbott had the highest pooled sensitivity (82.4% [95% CI 74.2-88.4] and 76.9% [95% CI 72.1-81.2], respectively). Sensitivity in high-viral-load samples (cycle threshold ≤25) showed heterogeneity among the different RATs. CONCLUSION: The RATs offered by Roche Diagnostics/SD Biosensor and Abbott provide sufficient manufacturer-independent, real-world performance data to support their use to detect current SARS-CoV-2 infection, particularly in high-viral-load populations.