Serological testing for SARS‐CoV‐2 antibodies in clinical practice: A comparative diagnostic accuracy study

Abstract

Background Serological tests are a powerful tool in the monitoring of infectious diseases and the detection of host immunity. However, manufacturers often provide diagnostic accuracy data generated through biased studies, and the performance in clinical practice is essentially unclear. Objectives We aimed to determine the diagnostic accuracy of various serological testing strategies for (a) identification of patients with previous coronavirus disease‐2019 (COVID‐19) and (b) prediction of neutralizing antibodies against SARS‐CoV‐2 in real‐life clinical settings. Methods We prospectively included 2573 consecutive health‐care workers and 1085 inpatients with suspected or possible previous COVID‐19 at a Swiss University Hospital. Various serological immunoassays based on different analytical techniques (enzyme‐linked immunosorbent assays, ELISA; chemiluminescence immunoassay, CLIA; electrochemiluminescence immunoassay, ECLIA; and lateral flow immunoassay, LFI), epitopes of SARS‐CoV‐2 (nucleocapsid, N; receptor‐binding domain, RBD; extended RBD, RBD+; S1 or S2 domain of the spike [S] protein, S1/S2), and antibody subtypes (IgG, pan‐Ig) were conducted. A positive real‐time PCR test from a nasopharyngeal swab was defined as previous COVID‐19. Neutralization assays with live SARS‐CoV‐2 were performed in a subgroup of patients to assess neutralization activity (n = 201). Results The sensitivity to detect patients with previous COVID‐19 was ≥85% in anti‐N ECLIA (86.8%) and anti‐S1 ELISA (86.2%). Sensitivity was 84.7% in anti‐S1/S2 CLIA, 84.0% in anti‐RBD+LFI, 81.0% in anti‐N CLIA, 79.2% in anti‐RBD ELISA, and 65.6% in anti‐N ELISA. The specificity was 98.4% in anti‐N ECLIA, 98.3% in anti‐N CLIA, 98.2% in anti‐S1 ELISA, 97.7% in anti‐N ELISA, 97.6% in anti‐S1/S2 CLIA, 97.2% in anti‐RBD ELISA, and 96.1% in anti‐RBD+LFI. The sensitivity to detect neutralizing antibodies was ≥85% in anti‐S1 ELISA (92.7%), anti‐N ECLIA (91.7%), anti‐S1/S2 CLIA (90.3%), anti‐RBD+LFI (87.9%), and anti‐RBD ELISA (85.8%). Sensitivity was 84.1% in anti‐N CLIA and 66.2% in anti‐N ELISA. The specificity was ≥97% in anti‐N CLIA (100%), anti‐S1/S2 CLIA (97.7%), and anti‐RBD+LFI (97.9%). Specificity was 95.9% in anti‐RBD ELISA, 93.0% in anti‐N ECLIA, 92% in anti‐S1 ELISA, and 65.3% in anti‐N ELISA. Diagnostic accuracy measures were consistent among subgroups. Conclusions The diagnostic accuracy of serological tests for SARS‐CoV‐2 antibodies varied remarkably in clinical practice, and the sensitivity to identify patients with previous COVID‐19 deviated substantially from the manufacturer's specifications. The data presented here should be considered when using such tests to estimate the infection burden within a specific population and determine the likelihood of protection against re‐infection.

Diagnostic accuracy of SARS-CoV-2 saliva antigen testing in a real-life clinical setting

“…Sample material was processed within 15 minutes (saliva antigen test) or 12 hours (RT-PCR, stored at 4 °C), respectively. De-tails of the RT-PCR determination have been reported previously ( Brigger et al, 2021, Horn et al, 2022, Jegerlehner et al, 2021.…”

Determination of the Diagnostic Performance of Laboratory Tests in the Absence of a Perfect Reference Standard: The Case of SARS-CoV-2 Tests

“…Details have been given elsewhere [ 15 ]. Two real-time PCRs were performed (Roche cobas ® SARS-CoV-2; Seegene Allplex 2019-nCoV), following the manufacturers’ instructions, on a STARlet IVD System or a cobas 8800 system, as has been previously described [ 16 , 18 ]. RT-PCR was performed as part of the daily routine without the laboratory technicians knowing the antigen test result.…”

The Impact of Clinical Factors and SARS-CoV-2 Variants on Antibody Production in Vaccinated German Healthcare Professionals Infected Either with the Delta or the Omicron Variant

“…Here, we are referring to anti-SARS-CoV-2 antibodies targeting the Spike (S) or Receptor-Binding Domain (RBD). In contrast, the detection of anti-Nucleocapsid (N) antibodies indicates a previous infection, as no vaccine was included in the study cohort that featured the nuclear capsid as an antigen target structure [ 6 , 7 ]. This may lead to an unpredictable response from individuals who experience a less severe course of COVID-19 due to previous vaccination.…”