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

Angelo Virgilio Paradiso; Simona De Summa; Daniela Loconsole; Vito Procacci; Anna Sallustio; Francesca Centrone; Nicola Silvestris; Vito Cafagna; Giuseppe De Palma; Antonio Tufaro; Vito Garrisi; Maria Chironna

Regarding the degree of concordance between the two tests, the results reported in Table 1 clearly show that the precision of the rapidserological test Viva-Diag TM is unsatisfactory. Notably, only 43% of the patients that were COVID-19-positive with the molecular test were also positive with serological test. This figure is impressively similar to the performances reported for serological tests in Spain (11) and Germany (12). However, the first important information from our study concerns the 12% of cases that tested negative with molecular test but had positive serological results. The two tests do not produce similar results as would be obvious for assays that look at different aspects of Covid-19; in fact, the molecular test demonstrates the presence of SARS-CoV-2 virus in samples from specific anatomical parts of the respiratory system while the kinetics of immunoglobulinsis devoted to describe as the body reacts to the viral infection. Negative serological test results in patients with a positive molecular test could mean that the latter are infected subjects that have not yet reached the stage of developing an immunoglobulin reaction; conversely, subjects whose serological tests show the presence of specific IgG and/or IgM antibodies and have negative molecular tests, may be considered as recovering from COVID-19. The data shown in Figure 1 seem to confirm these assumptions as the molecular test yielded more positive results in early symptomatic phases of the disease while the serological test performed better in the late phases of the disease (i.e. 10 days after symptom appearance).