Evaluation of Commercial Rapid Lateral Flow Tests, Alone or in Combination, for SARS-CoV-2 Antibody Testing.

Antibody tests can be tools for detecting current or past severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 [coronavirus disease 2019 (COVID-19)]) infections. Independent test evaluations are needed to document the performance with different sample sets. We evaluated six lateral flow assays (LFAs) and two laboratory-based tests (EUROIMMUN-SARS-CoV-2 ELISA and Abbott-Architect-SARS-CoV-2-IgG). We tested 210 plasma samples from 89 patients diagnosed with acute COVID-19. These samples were collected at different time points after the onset of symptoms. In addition, 80 convalescent plasma samples, and 168 pre-pandemic samples collected from adults in the United States and in Africa were tested. LFA performance varied widely, and some tests with high sensitivity had low specificity. LFA sensitivities were low (18.8-40.6%) for samples collected 0 to 3 days after symptom onset, and were greater (80.3-96.4%) for samples collected > 14 days after symptom onset. These results are similar to those obtained by ELISA (15.6% and 89.1%) and chemiluminescent microparticle assay (21.4% and 93.1%). The range of test specificity was between 82.7% and 97%. The combined use of two LFAs can increase specificity to more than 99% without a major loss of sensitivity. Because of suboptimal sensitivity with early COVID-19 samples and background reactivity with some pre-pandemic samples, none of the evaluated tests alone is reliable enough for definitive diagnosis of COVID-19 infection. However, antibody testing may be useful for assessing the status of the epidemic or vaccination campaign. Some of the LFAs had sensitivities and specificities that were comparable to those of more expensive laboratory tests, and these may be useful for seroprevalence surveys in resource-limited settings.