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

C S Lau; S P Hoo; Y L Liang; S K Phua; T C Aw

doi:10.1016/j.plabm.2021.e00201

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

Pract Lab Med. 2021 Mar:24:e00201. doi: 10.1016/j.plabm.2021.e00201. Epub 2021 Jan 19.

Authors

C S Lau¹, S P Hoo¹, Y L Liang¹, S K Phua¹, T C Aw^{1

2

3}

Affiliations

¹ Department of Laboratory Medicine, Changi General Hospital, Singapore.
² Department of Medicine, National University of Singapore, Singapore.
³ Academic Pathology Program, Duke-NUS Medical School, Singapore.

Abstract

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 = 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.

Keywords: Antibodies; Assay evaluation; Point-of-care testing; SARS-CoV-2.