Abstract
Several tests based on chemiluminescence immunoassay techniques have become available to test for SARS-CoV-2 antibodies. There is currently insufficient data on serology assay performance beyond 35 days after symptoms onset. We aimed to evaluate SARS-CoV-2 antibody tests on three widely used platforms. A chemiluminescent microparticle immunoassay (CMIA; Abbott Diagnostics, USA), a luminescence immunoassay (LIA; Diasorin, Italy), and an electrochemiluminescence immunoassay (ECLIA; Roche Diagnostics, Switzerland) were investigated. In a multigroup study, sensitivity was assessed in a group of participants with confirmed SARS-CoV-2 (n = 145), whereas specificity was determined in two groups of participants without evidence of COVID-19 (i.e., healthy blood donors, n = 191, and healthcare workers, n = 1002). Receiver operating characteristic (ROC) curves, multilevel likelihood ratios (LR), and positive (PPV) and negative (NPV) predictive values were characterized. Finally, analytical specificity was characterized in samples with evidence of the Epstein–Barr virus (EBV) (n = 9), cytomegalovirus (CMV) (n = 7), and endemic common-cold coronavirus infections (n = 12) taken prior to the current SARS-CoV-2 pandemic. The diagnostic accuracy was comparable in all three assays (AUC 0.98). Using the manufacturers' cut-offs, the sensitivities were 90%, 95% confidence interval [84,94] (LIA), 93% [88,96] (CMIA), and 96% [91,98] (ECLIA). The specificities were 99.5% [98.9,99.8] (CMIA), 99.7% [99.3,99.9] (LIA), and 99.9% [99.5,99.98] (ECLIA). The LR at half of the manufacturers' cut-offs were 60 (CMIA), 82 (LIA), and 575 (ECLIA) for positive and 0.043 (CMIA) and 0.035 (LIA, ECLIA) for negative results. ECLIA had higher PPV at low pretest probabilities than CMIA and LIA. No interference with EBV or CMV infection was observed, whereas endemic coronavirus in some cases provided signals in LIA and/or CMIA. Although the diagnostic accuracy of the three investigated assays is comparable, their performance in low-prevalence settings is different. Introducing gray zones at half of the manufacturers' cut-offs is suggested, especially for orthogonal testing approaches that use a second assay for confirmation.
Highlights
COVID-19 is a recently emerging pandemic disease caused by infection with SARS-CoV-2 virus
The first group of patients was retrospectively assembled from Liechtenstein and Swiss patients having their laboratory evaluations sent to labormedizinisches zentrum Dr Risch in Vaduz (Liechtenstein) and Buchs (Switzerland) and consisted of COVID-19 patients whose serum was drawn after COVID-19 disease was confirmed by RT-PCR between March 2nd and April 23rd, 2020 (n = 145)
The group of RT-PCR confirmed COVID-19 patients consisted of 145 individuals with a median age of 46 years (IQR [30,58] years), and 79 of the patients, i.e., 48%, were female
Summary
COVID-19 is a recently emerging pandemic disease caused by infection with SARS-CoV-2 virus. After several countries showed success in confining the progression of the COVID-19 pandemic with drastic measures, there is a need to gradually cancel these measures to reinstitute possibly “normal” social and economic circumstances [12, 13]. To guide these actions to reverse socioeconomic lockdown, knowledge on the prevalence of COVID-19 is needed [14]. Since a large proportion of patients with suspected COVID-19 infection could not be tested by RT-PCR in the acute phase, serological testing may gain increasing importance for retrospective clarification of clinical symptoms [15]
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