Comparison of different serological assays for SARS-CoV-2 in real life

Abstract

Background: The emergence of the global SARS-CoV-2 pandemic required the rapid and large-scale deployment of PCR and serological tests in different formats.

Objectives: Real-life evaluation of these tests is needed. Using 168 samples from patients hospitalized for COVID-19, non-hospitalized patients but infected with SARS-CoV-2, patients participating in screening campaigns, and samples from patients with a history of other seasonal coronavirus infections, we evaluated the clinical performance of 5 serological assays widely used worldwide (WANTAI®, BIORAD®, EUROIMMUN®, ABBOTT® and LIAISON®).

Results: For hospitalized patients, all these assays showed a sensitivity of 100 % from day 9 after the symptoms onset. On the other hand, sensitivity was much lower for patients who did not require hospitalization for COVID-19 confirmed by PCR (from 91.6 % for WANTAI® to 69 % for LIAISON®). These differences do not seem to be due to the antigens chosen by the manufacturers but more to the test formats (IgG detection versus total antibodies). In addition, more than 50 days after a positive PCR for CoV-2-SARS the proportion of positive patients seem to decrease. We did not observe any significant cross-reactions for these techniques with the four other seasonal coronaviruses.

Conclusion: In conclusion, the evaluation and knowledge of the serological tests used is important and should require an optimized strategy adaptation of the analysis laboratories to best meet patient's expectations in the face of this health crisis.

Keywords: COVID-19; Performance assays; SARS-CoV-2; Serological assays.

Fig. 1

Percentages of positive patient samples for the 5 serological techniques evaluated according to patient group (A) and according to the delay between SARS-CoV-2 PCR and serology for the first two patient groups (B).

Fig. 2

Index of the different evaluated assays for the 4 groups of patients. The dotted lines correspond to the positivity thresholds defined by the different manufacturers and the continuous lines to the median values.