Abstract
BACKGROUND: Despite widespread vaccination, SARS-CoV-2 transmission continues, and serological testing remains relevant for selected diagnostic scenarios and population-based assessments of antibody responses. Rapid diagnostic tests (RDTs) for SARS-CoV-2 antibodies are attractive for field use and decentralized settings, but their diagnostic performance varies and requires independent evaluation. We assessed the performance of three commercially available lateral flow RDTs (PANBIO™ COVID-19 IgG/IgM Rapid Test Device, Bio-Manguinhos-Fiocruz TR COVID-19 (IgM-IgG), and Bio-Manguinhos-Fiocruz TR DPP® COVID-19 IgM/IgG) in Salvador, Brazil. METHODS: Using blind analyses, we evaluated 257 serum samples from RT-PCR-confirmed cases and 199 control samples from individuals with other febrile illnesses or healthy donors collected before and during the pandemic. RESULTS: Overall sensitivity for IgM or IgG detection was limited across all tests (52%-58%), while specificity was high for two assays (97%-98%) and lower for one (80%). Sensitivity peaked between 11 and 20 days after symptom onset (80%-91%) and declined thereafter. Among 75 vaccinated individuals without prior COVID-19, antibody positivity ranged from 39% to 55%. CONCLUSION: These findings indicate that the evaluated RDTs had high specificity but insufficient sensitivity for reliable clinical diagnosis or for assessing vaccination status in serological surveys. Our results support cautious use of these assays and highlight the need for more accurate and robust antibody-based rapid tests to strengthen immunological surveillance and public health preparedness in the post-pandemic period.