Highlights An extensive evaluation of the Abbott SARS-CoV-2 IgG assay. The assay shows excellent sensitivity/specificity with little cross-reactivity. Healthy volunteers and pre-pandemic samples had similar antibody cut-off indexes. A lower, optimised limit for reactivity improves sensitivity in early disease.

Background Little is known about the performance of the Roche novel severe acute respiratory syndrome coronavirus 2 antibody (anti-SARS-CoV-2) assay. We provide an extensive evaluation of this fully automated assay on the Cobas e801/e602 immunoassay analysers. Methods We assessed the linearity, precision, and throughput of the Roche anti-SARS-CoV-2 assay. Sensitivity was calculated from 349 SARS-CoV-2 polymerase chain reaction (PCR) positive samples; specificity was determined from 715 coronavirus disease 2019 (COVID-19)-naive samples. We examined cross-reactivity against other antibody positive samples (syphilis, RF, ANA, ds-DNA, influenza, dengue, HBV, HCV) and the anti-SARS-CoV-2 kinetics. Results The assay cut-off index (COI) was linear up to 90.8. The inter-assay precision was 2.9% for a negative control (COI=0.1) and 5.1% for a positive control (COI=3.0). Assay time is 18min and results are available 1 minute later; throughput for 300 samples was 76 minutes. Only 1 case positive for HBsAg tested falsely positive; specificity was 99.9%. The assay has a sensitivity of 97.1% 14 days after PCR positivity (POS) and 100% at ≥ 21 days POS; 48.2% of cases had anti-SARS-CoV-2 within 6 days POS. In 11 subjects in whom serum was available prior to a positive antibody signal (COI ≥1.0) the interval between the last negative and first positive COI (time to “sero-conversion”) on average is 3 days (range 1-6 days) and 4 more days (range 1-7) for the anti-SARS-CoV-2 to plateau. Conclusion The Roche anti-SARS-CoV-2 assay shows excellent performance with minimal cross-reactivity from other viral and confounding antibodies. Antibody development and sero-conversion appears quite early.

Background: Little is known about the performance of the Roche novel severe acute respiratory syndrome coronavirus 2 antibody (anti-SARS-CoV-2) assay. We provide an extensive evaluation of this fully automated assay on the Cobas e801/e602 immunoassay analysers. Methods: We assessed the linearity, precision, and throughput of the Roche anti-SARS-CoV-2 assay. Sensitivity was calculated from 349 SARS-CoV-2 polymerase chain reaction (PCR) positive samples; specificity was determined from 714 coronavirus disease 2019 (COVID-19)-naive samples. We examined cross-reactivity against other antibody positive samples (syphilis, RF, ANA, ds-DNA, influenza, dengue, HBV, HCV) and the anti-SARS-CoV-2 kinetics. Results: The assay cut-off index (COI) was linear up to 90.7. The inter-assay precision was 2.9% for a negative control (COI=0.1) and 5.1% for a positive control (COI=3.0). Assay time is 18min and results are available 1 minute later; throughput for 300 samples was 76 minutes. No cross-reactivity was observed with other antibody positive samples; specificity was 100%. The assay has a sensitivity of 97.1% 14 days after PCR positivity (POS) and 100% at ≥21 days POS; 48.2% of cases had anti-SARS-CoV-2 within 6 days POS. In 11 subjects in whom serum was available prior to a positive antibody signal (COI ≥1.0) the interval between the last negative and first positive COI (time to sero-conversion) on average is 3 days (range 1-6 days) and 4 more days (range 1-7) for the anti-SARS-CoV-2 to plateau. Conclusion: The Roche anti-SARS-CoV-2 assay shows excellent performance with minimal cross-reactivity from other viral and confounding antibodies. Antibody development and sero-conversion appears quite early.

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Introduction We evaluated the Roche Elecsys IL6 assay on the Cobas immunoassay analyser. Method Serum IL6 of 144 controls were compared to 52 samples from patients with COVID-like respiratory symptoms (17 SARS-CoV-2 RT-PCR positive); 25 of these were from the intensive care unit (ICU). We compared the IL6 levels to C-reactive protein (CRP) and procalcitonin (PCT) levels in all cases. Results The IL6 assay had coefficient-of-variation (CV) of 2.3% (34.1 pg/mL) and 2.5% (222.5 pg/mL), a limit of quantitation <1.6 pg/mL, and was linear from 1.6-4948pg/mL. There was a significant difference in IL6 values between patients with COVID-like respiratory symptoms versus controls (p < 0.001). ROC analysis showed that IL6 > 6.4 pg/mL identified symptomatic cases (AUC 0.94, sensitivity 88.2%, specificity 97.2%). There was a significant difference between the IL6 of symptomatic ICU/non-ICU cases (median IL6 228 vs 11 pg/mL, p < 0.0001); ROC analysis showed IL6 > 75 pg/mL (sensitivity 76.0%, specificity 88.9%) was superior to CRP and PCT in predicting ICU admission (AUC: IL6 0.83, CRP 0.71, PCT 0.82). Conclusion The performance of Elecsys IL6 assay is in keeping with the manufacturer’s claims. IL6 > 6.4 pg/mL differentiates healthy from suspected COVID-19 cases and appears to be raised earlier than the other inflammatory markers in some cases. IL6 > 75 pg/mL was a good predictor of ICU admission.