Comparison of Performance between the Elecsys 4th and 5th Generation STAT Cardiac Troponin T Immunoassays.

OBJECTIVE: To evaluate the analytical and clinical performance of the 5th GEN cTnT assay by comparing it with the 4th GEN assay. METHODS: Imprecision, analytical measurement range (AMR), reference interval, and quantitative comparison were studied. Qualitative comparisons of the two assays for randomly selected patients with the cTnT test orders and patients with elevated N-terminal proB-type natriuretic peptide (NT-proBNP), decreased estimated glomerular filtration rate (eGFR), and increased procalcitonin were performed. RESULTS: Within-run and between-run CVs of the 5th GEN assay were 0.6-2.3% and 3.1-5.0% with AMR of 8-10,000 ng/L and reference interval of <19 ng/L. Regression analysis of the two assays showed linear relationship: y (5th GEN)=0.899x (4th GEN)+26, r=0.9993 with a positive bias of the 5th GEN assay in samples with cTnT <150 ng/L and a negative bias in samples with cTnT >500 ng/L compare to the 4th GEN assay. Agreement was 88.1% (95% CI: 80.4 to 93.1%) between the two methods according to the 99th percentile threshold. In patients with elevated NT-proBNP, decreased eGFR, and increased procalcitonin, agreements were 79.4%, 92.7%, and 100%. CONCLUSION: The 5th GEN cTnT assay demonstrates excellent precision and acceptable AMR. Compared to the 4th GEN assay, the 5th GEN assay shows a negative bias for samples with cTnT >500 ng/L but a positive bias for samples with cTnT <150 ng/L and identifies more patients with elevated cTnT.

Analytical and Clinical Analysis of Two Automated Anti-SARS-CoV-2 Immunoassays in Pre-Pandemic and Pandemic Patient Populations.

BACKGROUND: In the absence of a safe, effective vaccine, the worldwide spread of COVID-19 (SARS-CoV-2) infection will continue. Laboratory tests with ideal precision, sensitivity, and specificity should be used in public health and clinical settings to gauge the extent of virus exposure. Toward this end, we evaluated the analytical and clinical performance of the Abbott SARS-CoV-2 IgG and the Roche Anti-SARS-CoV-2 immunoassays. METHODS: Quality control, pooled COVID-19, and non-COVID-19 patient specimens were used for the imprecision study. Two hundred and forty-six specimens from 70 patients with COVID-19 diagnosis were tested to study the sensitivity. Seventy-three non-COVID-19 control specimens were measured to study the specificity. All specimens were analyzed by both assays. RESULTS: Total analytic variability (CV) of the negative and positive controls were 5.5% and 3.6% for the Abbott assay and 4.5% and 1.9% for the Roche assay. Both assays demonstrated 100% qualitative reproducibility of negative and positive controls. The clinical specificities of the Abbott and the Roche assays were 100% (95% CI: 94%-100%) and 97% (95% CI: 90%-100%), respectively. The clinical sensitivities of the Abbott assay were 49% (95% CI: 41%-56%), 86% (95% CI: 74%-93%), and 100% (95% CI: 76%-100%) for samples collected at 0-6 days, 7-13 days, and ≥14 days after the first RT-PCR, while the sensitivities of the Roche assay were 55% (95% CI: 47%-62%), 86% (95% CI: 74%-93%), and 100% (95% CI: 76%-100%). CONCLUSIONS: This study demonstrates similar analytical and clinical performance of the Abbott and the Roche SARS-CoV-2 antibody assays, but the Roche assay may be slightly more sensitive for patients tested within 0-6 days after first positive RT-PCR of SARS-CoV-2.COVID-19 is a respiratory infectious disease caused by SARS-CoV-2. Laboratory tests with ideal precision, sensitivity, and specificity should be used in public health and clinical settings. We analyzed analytical and clinical performance of the Roche and Abbott SARS-CoV-2 antibody assays in pre-pandemic and pandemic patient populations. Additionally, we analyzed the sensitivity of both assays in patients at different stages of the disease. The 2 assays showed similar analytical and clinical performance, but the Roche assay may be slightly more sensitive for patients tested within 0-6 days after first positive RT-PCR of SARS-CoV-2. Our findings help other clinical labs select appropriate assays for SARS-CoV-2 antibody testing.

Automated Measurement of Plasma Cell-Free Hemoglobin Using the Hemolysis Index Check Function.

BACKGROUND: The Roche Cobas chemistry analyzer's hemolysis index (HI) check function can directly report hemoglobin (Hb) concentrations. We aimed to validate the HI check function for the measurement of plasma cell-free Hb. METHODS: Plasma samples (6 µl) were taken by the analyzer and diluted in normal saline to measure the absorbance for Hb at 570 and 600 nm. Hb concentrations were calculated based on the molar extinction coefficient. Imprecision, lower limit of quantification (LLOQ), and analytical measurement range (AMR) of the assay were evaluated. The accuracy was determined by comparing the results between the new method and an existing spectrophotometric method. We further studied interference of icterus and lipemia and carryover. The performance of the assay in proficiency testing was also evaluated. The reference range was transferred from the existing method. RESULTS: Within-run and total CVs were 1.7%-4.2% and 2.1%-7.0%, respectively (n = 20). The LLOQ was 11 mg/dL (CV = 8.1%) with the upper limit of AMR of 506 mg/dL. The results of the new method correlated well with the existing reference assay: Y (new method) = 0.974 x (reference method) + 4.9, r = 0.9990, n = 52. Bilirubin with a concentration up to 60 mg/dL and lipemic index up to 389 did not show significant interference. No significant carryover was detected. The average standard deviation index in proficiency testing was 0.03 ± 0.29. The reference range was <22 mg/dL. CONCLUSIONS: Plasma cell-free Hb measurement using the HI check function meets the analytical requirements of the plasma cell-free Hb assays. It is simple and cost-effective.