Head-to-Head Accuracy Comparison of Three Commercial COVID-19 IgM/IgG Serology Rapid Tests.

Background: Comparative data of SARS-CoV-2 IgM/IgG serology rapid diagnostic tests (RDTs) is scarce. We thus performed a head-to-head comparison of three RDTs.

Methods: In this unmatched case-control study, blood samples from 41 RT-PCR-confirmed COVID-19 cases and 50 negative controls were studied. The diagnostic accuracy of three commercially available COVID-19 RDTs: NTBIO (RDT-A), Orient-Gene (RDT-B), and MEDsan (RDT-C), against both a recombinant spike-expressing immunofluorescence assay (rIFA) and Euroimmun IgG ELISA, was assessed. RDT results concordant with the reference methods, and between whole blood and plasma, were established by the Kendall coefficient.

Results: COVID-19 cases' median time from RT-PCR to serology was 22 days (interquartile range (IQR) 13-31 days). Whole-blood IgG detection with RDT-A, -B, and -C showed 0.93, 0.83, and 0.98 concordance with rIFA. Against rIFA, RDT-A sensitivity (SN) was 92% (95% CI: 78-98) and specificity (SP) 100% (95% CI: 91-100), RDT-B showed 87% SN (95% CI: 72-95) and 98% SP (95% CI: 88-100), and RDT-C 100% SN (95% CI: 88-100) and 98% SP (95% CI: 88-100). Against ELISA, SN and SP were above 90% for all three RDTs.

Conclusions: RDT-A and RDT-C displayed IgG detection SN and SP above 90% in whole blood. These RDTs could be considered in the absence of routine diagnostic serology facilities.