Rapid serological and SARS-CoV-2 RT-PCR assays: comparison performed simultaneously in symptomatic COVID-19 patients

BACKGROUND: RT-PCR testing for the identification of viral nucleic acid is the current standard diagnostic method for the diagnosis of SARS-CoV-2 infection but technical reasons limit its utilization for large-scale screening Serological IgM/IgG testing has been proposed as a useful tool to detect SARS-CoV-2 exposure OBJECTIVE: The objective of our study was to compare the results provided by the rapid serological VivaDiag™ test for SARS-CoV-2-related IgM/IgG detection with those of the standard RT-PCR laboratory test for virus acid-nucleic identification METHODS: We simultaneously performed both serological and molecular tests in a consecutive series of 191 symptomatic patients The results provided by a new rapid serological colorimetric test analyzing IgM/IgG expression were compared with those of RT-PCR testing for SARS-CoV-2 detection RESULTS: 70 out of 191 subjects (37%) had positive SARS-CoV-2 RT-PCR results while 33 (18%) a positive IgM and/or/IgG results 13 subjects (7%) had positive serological test results and negative RT-PCR results The rapid serological test showed a sensitivity of 30% and a specificity of 89% compared to the standard RT-PCR assay but, interestingly, these performances improved 8 days after symptom appearance After 10 days of symptoms, the predictive value of the rapid serological test was higher than that of the standard molecular assay Multivariate analysis showed that age>58 yrs and more than 15 days from symptom onset were significantly and independently associated with serological test positivity CONCLUSIONS: The rapid serological test analyzed in the present study seems of limited usefulness for the diagnosis of SARS-CoV-2 infection but it is a candidate test for providing relevant information on the immunoreaction of subjects to COVID-19 exposure