Thorax computed tomography findings and anti-SARS-CoV-2 immunoglobulin G levels in polymerase chain reaction-negative probable COVID-19 cases.

Abstract

OBJECTIVE: This study aimed to evaluate the SARS-CoV-2 immunoglobulin G (IgG) levels after 6 months of polymerase chain reaction (PCR) negativebut assumed to be COVID-19 positive cases to investigate the relationship between IgG levels and thoracic computed tomography (CT) findings.METHODS: This was a single-center study that included patients whose PCR test results were negative at least three times using nasopharyngealswabs but had clinical findings of COVID-19 and thoracic CT findings compatible with viral pneumonia. Six months after discharge, the IgG antibodieswere analyzed. The cutoff value for negative and positive serology was defined as <1.4 (index S/C) and ≥1.4 (index S/C), respectively. In addition, thepatients were categorized according to their thoracic CT findings as high (typical) and low (atypical). Also, the patients were grouped into classes as<5% lung involvement versus ≥5% lung involvement.RESULTS: The patients’ mean age was 49.78±12.96 years. PCR was negative, but patients with COVID-19 symptoms who had SARS-CoV-2 IgGpositive were 81.9% (n=95). The antibody titer and lung involvement ≥5% were statistically significantly higher in SARS-CoV-2 IgG positive cases(p<0.001 and p=0.021). Age and chest CT findings were the risk factors for lung involvement (OR=1.08, p<0.001 and OR=2.19, p=0.010, respectively).CONCLUSION: This study is valuable because increasing severity (≥5%) of lung involvement appears to be associated with high and persistent IgGantibody titers. In probable cases of COVID-19, even if the PCR test is negative, high IgG titers 6 months after discharge can predict the rate of lungparenchymal involvement.