Antibody response in patients admitted to the hospital with suspected SARS-CoV-2 infection: results from a multicenter study across Spain

Abstract

Aim: To evaluate the serological response against SARS-CoV-2 in a multicenter study representative of the Spanish COVID pandemic.

Methods: IgG and IgM + IgA responses were measured on 1466 samples from 1236 Spanish COVID-19 patients admitted to the hospital, two commercial ELISA kits (Vircell SL, Spain) based on the detection of antibodies against the viral spike protein and nucleoprotein, were used.

Results: Approximately half of the patients presented antibodies (56.8% were IgM + IgA positive and 43.0% were IgG positive) as soon as 2 days after the first positive PCR result. Serological test positivity increased with time from the PCR test, and 10 days after the first PCR result, 91.5% and 88.0% of the patients presented IgM + IgA and IgG antibodies, respectively.

Conclusion: The high values of sensitivity attained in the present study from a relatively early period of time after hospitalization support the use of the evaluated serological assays as supplementary diagnostic tests for the clinical management of COVID-19.

Keywords: COVID-19; Diagnosis; IgA; IgG; IgM; SARS-COV-2.

Fig. 1

Dynamic trend of the positive rate for IgG and IgM + IgA in sera of RT-PCR-positive patients

Fig. 2

Serology test results for positive PCR patients grouped by age. Bar heights represent absolute frequencies. a Data from all PCR-positive patients, b results corresponding to samples collected in the first week after the first PCR result, and c results corresponding to samples collected later than one week after the first PCR result

Fig. 3

IgG and IgM + IgA index value (10 X serum/cutoff) boxplot for all PCR-positive patients distinguishing between male and female and grouped by age. Boxes encompass 90% of the data, and whiskers present the 95% and 5% percentiles