Performance of the Roche/Snibe electrochemiluminescent anti-SARS-COV-2 spike assays compared to the Roche/Abbott IgG nucleocapsid and Abbott IgM spike assays.

INTRODUCTION: We evaluated the Roche Elecsys Anti-SARS-CoV-2 and Snibe SARS-CoV-2 S-RBD IgG spike chemiluminescent immunoassays and compared them to existing Roche/Abbott nucleocapsid and Abbott IgM spike assays. METHODS: We enrolled 184 SARS-CoV-2 RT-PCR positive samples and 215 controls (172 pre-pandemic, and 43 cross-reactivity) to evaluate the Roche spike antibody (anti-SARS-CoV-2-S) assay. For the Snibe evaluation, we included 119 RT-PCR positive samples and 249 controls (200 pre-pandemice, 49 cross-reactivity). 98 cases had been tested on three spike assays (Roche total antibody, Snibe IgG and Abbott IgM). RESULTS: The Roche anti-SARS-CoV-2-S assay had a CV of 0.5% (0.82U/mL) and 2.3% (8.72U/mL) and was linear from 1.16 to 240U/mL. The Snibe assay was linear from 6.43 to 77.7AU/mL, CV of 5.5% (0.43AU/mL) and 8.8% (0.18AU/mL). The Snibe spike assay was significantly more sensitive than the Abbott IgG assay at 0-6 days POS (35.2% vs 3.6%, mean difference 29.6%, 95% CI 17.5 to 41.8, p < 0.0001). Optimized LORs significantly improved the sensitivity of the Roche spike (48.1%-56.7%) and both nucleocapsid assays (Roche 43.3%-65.5%, Abbott 3.6%-18.5%) in early disease. CONCLUSION: Although both spike assays showed higher sensitivity than their nucleocapsid counterparts, lower, optimized LORs provided the most significant improvements to sensitivity.

Performance of the Roche IL-6 chemiluminescent immunoassay in patients with COVID-like respiratory symptoms.

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 to 4948 pg/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.

Performance of two rapid point of care SARS-COV-2 antibody assays against laboratory-based automated chemiluminescent immunoassays for SARS-COV-2 IG-G, IG-M and total antibodies.

INTRODUCTION: We evaluated two SARS-CoV-2 antibody point-of-care tests (POCTs) (Abbott Panbio COVID-19 IgG/IgM and Roche SARS-CoV-2 Rapid Antibody tests) and compared the results to their respective chemiluminescent immunoassays (CLIAs) (Abbott Architect IgM, Architect IgG, Roche Cobas total antibody assays). METHOD: 200 pre-pandemic sera and 48 samples positive for various conditions (18 viral hepatitis, 18 dengue, 11 ANA and 1 dsDNA) were used as controls and to assess for cross-reactivity. Anonymised residual leftover sera positive for SARS-CoV-2 on RT-PCR were recruited as cases (n â€‹= â€‹133). The sensitivity/specificity/cross-reactivity/positive predictive value (PPV)/negative predictive value (NPV) of the POCTs were assessed. Concordance between the POCTs and chemiluminescent immunoassays (CLIAs) were analysed. RESULTS: Abbott/Roche POCT specificity was 98.7%/100% (95% CI 96.5-99.8/98.5-100) and sensitivity was 97.2%/97.2% (95% CI 85.5-99.9/85.5-99.9) in cases ≥14 days post-first positive RT-PCR (POS), PPV was 68.7%/100% (95% CI 41.3-87.2/94.7-100.0), and NPV was 97.4%/97.6% (95% CI 97.0-97.8/97.2-98.0). In cases ≥14 days POS, concordance of Abbott/Roche POCT and CLIAs was 97.2%/100% (35/36 and 36/36 results). The sensitivity of individual IgM-band results on both POCTs did not increase >95% even after 14 days POS (Abbott 2.78%, Roche 44.4%). CONCLUSION: Both POCTs have good specificity, little cross-reactivity with other antibodies, and sensitivity >95% when used in subjects ≥14 days POS. Analysis of individual POCT IgG/IgM-bands did not provide any additional information. POCTs can substitute for CLIAs in cases ≥14 days POS. In low prevalence areas, POCTs would be especially useful when combined with antigen testing in an orthogonal format to increase the PPV of COVID-19 results.

Performance of an automated chemiluminescence SARS-CoV-2 IG-G assay.

INTRODUCTION: We describe our evaluation of the Abbott SARS-CoV-2 IgG assay on the Architect immunoassay analyser. METHODS: We assessed assay precision, sensitivity, specificity, positive/negative predictive values (PPV/NPV), cross-reactivity (influenza/dengue/hepatitis B and C/rheumatoid factor/anti-nuclear/double-stranded DNA/syphilis) and sample throughput in samples from real-time polymerase chain reaction (RT-PCR) positive patients/healthcare workers (HCWs)/pre-pandemic samples. We compared the cut-off indexes (COIs) between all control samples (HCWs and pre-pandemic) to generate an optimised COI limit for reactivity. RESULTS: The assay specificity was 99.8% (n = 980) and sensitivity was 45.9-96.7% (n = 279). When tested ≥ 14 days post-positive RT-PCR (POS), the PPV/NPV was 96.4%/99.8%. The difference between the COIs of HCWs/pre-pandemic samples was small (0.01, p < 0.0001). There was minimal cross-reactivity with other antibodies. A lower COI limit for reactivity (≥0.55, using the 99th percentile COI of our controls and ROC analysis) improved diagnostic sensitivity, especially at 0-6 days POS (45.9-55.8%), with a small decrease in specificity (98.9%). The assay throughput was 100 samples in 70 min. CONCLUSION: The Abbott SARS-CoV-2 IgG assay shows excellent performance in patients ≥ 14 days POS. The difference between the COIs of HCWs and pre-pandemic samples was numerically small. A lower COI limit improves assay sensitivity with a slight decrease in specificity.

Evaluation of an Electrochemiluminescent SARS-CoV-2 Antibody Assay.

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 Cobas e801/e602 immunoassay analyzers. 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, rheumatoid factor (RF), antinuclear antibody (ANA), double-stranded DNA (ds-DNA), influenza, dengue, hepatitis B (HBV), hepatitis C (HCV)] and the anti-SARS-CoV-2 kinetics. RESULTS: The assay cut-off index (COI) was linear up to 90.8. The interassay precision was 2.9% for a negative control (COI = 0.1) and 5.1% for a positive control (COI = 3.0). Assay time is 18 min and results are available 1 min later; throughput for 300 samples was 76 min. 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 patients 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 "seroconversion") 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 seroconversion appears quite early.

Tuning the surface properties of hydrogel at the nanoscale with focused ion irradiation.

With the site-specific machining capability of Focused Ion Beam (FIB) irradiation, we aim to tailor the surface morphology and physical attributes of biocompatible hydrogel at the nano/micro scale particularly for tissue engineering and other biomedical studies. Thin films of Gtn-HPA/CMC-Tyr hydrogels were deposited on a gold-coated substrate and were subjected to irradiation with a kiloelectronvolt (keV) gallium ion beam. The sputtering yield, surface morphology and mechanical property changes were investigated using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Monte Carlo simulations. The sputtering yield of the hydrogel was found to be approximately 0.47 µm(3) nC(-1) compared with Monte-Carlo simulation results of 0.09 µm(3) nC(-1). Compared to the surface roughness of the pristine hydrogel at approximately 2 nm, the average surface roughness significantly increased with the increase of ion fluence with measurements extended to 20 nm at 100 pC µm(-2). Highly packed submicron porous patterns were also revealed with AFM, while significantly decreased pore sizes and increased porosity were found with ion irradiation at oblique incidence. The Young's modulus of irradiated hydrogel determined using AFM force spectroscopy was revealed to be dependent on ion fluence. Compared to the original Young's modulus value of 20 MPa, irradiation elevated the value to 250 MPa and 350 MPa at 1 pC µm(-2) and 100 pC µm(-2), respectively. Cell culture studies confirmed that the irradiated hydrogel samples were biocompatible, and the generated nanoscale patterns remained stable under physiological conditions.