RESUMO
The WHO standard was prepared with the aim of harmonizing assays detecting antibodies against SARS CoV-2. The aspect of the harmonization of the assays is to date under debate. We re-evaluated a previously studied set of cases (108 specimens of 48 patients and 60 specimens of 20 vaccinated subjects, collected after 14 days from the first dose, 14 days and 3 months after a second dose of the Comirnaty BNT162b2 vaccine), calculating the ratios between the results of two methods (SARS-CoV-2 IgG anti-RBD, SNIBE and anti-SARS-CoV-2 QuantiVac ELISA IgG, Euroimmun). In the vaccinated subjects the ratios of the results between methods according to the WHO standard were relatively dispersed, but the harmonization results good. On the other hand, in patient samples the variability between tests was very high and the harmonization was unsatisfactory (median ratios between methods 2.23, 10th-90th percentile: 1.1-5.6). Interestingly, in patient samples the harmonization depends on the time from the onset of symptoms, and greatly improves after 6 months from the diagnosis. 40 patient specimens and 31 of vaccinated subjects after the second dose were evaluated also with a third method (Access SARS-CoV-2 IgG (1st IS), Beckman Coulter), obtaining a similar trend. We can conclude that the actual effectiveness of harmonization between methods may vary depending on the scenario in which they will be used.
RESUMO
The time-course of antibodies anti SARS-CoV2 is not yet well elucidated, especially in people who underwent a vaccination campaign. In this study we measured antibodies anti-S1 and anti-RBD with two different methods both in patients and in vaccinated subjects. 108 specimens from 48 patients diagnosed as COVID-19 affected (time from the onset of symptoms from 3 to 368 days) and 60 specimens from 20 vaccinated subjects (collected after 14 days from the first dose, 14 days and 3 months after a second dose of Comirnaty) were evaluated. We used an ELISA method that measure IgG against anti-Spike 1 and a chemiluminescence immunoassays that measure IgG anti-RBD. In the patients, antibodies concentrations tend to decline after a few months with both methods, but persist relatively high up to nearly a year after symptoms. In vaccinated subjects, antibodies were already detectable after the first dose, but after the booster they show a significant increase. However, the decrease is rapid, given that after 3 months after the second vaccination they are reduced to less than a quarter. The conversion of the results into BAU units improves the relationship between the two methods. However, in vaccinated subjects there was no evidence of proportional error after the conversion, while in the patients the difference between the two methods remained significant.
RESUMO
In order to identify the quantization capability of two methods for SARS-CoV-2 IgG determination (Anti-SARS-CoV-2 QuantiVac ELISA IgG from Euroimmun and SARS-CoV-2 IgG anti-RBD from SNIBE), the linearity of the reportable range with respect to the calibration curve was evaluated.
RESUMO
BackgroundThe role and significance of the immune response to SARS-CoV-2 infection is not yet well known. MethodsWe conducted a study on 46 symptomatic subjects with disease confirmed by laboratory tests, to evaluate the presence of IgG and IgM antibodies in these subjects in relation to the time elapsed since the onset of symptoms. The analytical performance of the method used in the study and the effect of two different serum and plasma matrices were also assessed. ResultsIgG positivity was demonstrated in 100% of cases 15 days after the onset of the disease. IgM show lower concentrations and do not exceed 77% of cases after 15 days. The analytical performance of the method used (Maglumi 800, Snibe, China) was confirmed to be good in terms of imprecision, linearity and commutability in two sample matrix. ConclusionThe serological study through the search for specific IgG for SARS-CoV-2 results to be sensitive and suitable for population research and evidences that this approach can also play an important role in diagnosis. The diagnostic performance of specific IgMs are lower.
