Clinical meanings of rapid serological assay in patients tested for SARS-Co2 RT-PCR

Background RT-PCR test for identifiction of viral nucleic acid is the current standard diagnostic method for the diagnosis of COVID-19 disease but technical reasons limit the utilization of this assay on large scale screenings. Method We verified in a consecutive series of 191 symptomatic patients the clinical information that new rapid serological colorimetric test qualitatively analyzing IgM/IgG expression can provide with respect to standard assay and with respect to clinical outcome of patients. Results Rapid serological test showed a sensitivity of 30% and a specificity of 89% with respect to the standard assay but, interestingly, these performances improve after 8 days of symptoms appearance. After 10 days of symptoms the predictive value of rapid serological test is higher than that of standard assay. When the behaviour of the two immunoglobulins was evaluated with respect to time length of symptoms appearance, no significant difference in immunoglobulins behaviour was shown. Conclusions The rapid serological test analyzed in the present study is candidate to provide information on immunoreaction of the subject to COVID-19 exposure.