Assessment of SARS-CoV-2 serological tests for the diagnosis of COVID-19 through the evaluation of three immunoassays: two automated immunoassays (Euroimmun and Abbott) and one rapid lateral flow immunoassay (NG Biotech)

Nicol, Thomas; Lefeuvre, Caroline; Serri, Orianne; Pivert, Adeline; Joubaud, Françoise; Ducancelle, Alexandra; Lunel-Fabiani, Françoise; Le Guillou-Guillemette, Hélène

BACKGROUND: The emergence of new SARS-CoV-2 has promoted the development of new serological tests that could be complementary to RT-PCR. Nevertheless, the assessment of clinical performances of available tests is urgently required as their use has just been initiated for diagnose. OBJECTIVES: The aim of this study was to assess the performance of three immunoassays for the detection of SARS-CoV-2 antibodies. METHODS: Two automated immunoassays (Abbott SARS-CoV-2 CLIA IgG and Euroimmun Anti-SARS-CoV-2 ELISA IgG/IgA assays) and one lateral flow immunoassay (LFIA NG-Test® IgG-IgM COVID-19) were tested. 293 specimens were analyzed from patients with a positive RT-PCR response, from patients with symptoms consistent with COVID-19 but exhibiting a negative response to the RT-PCR detection test, and from control group specimens. Days since symptoms onset were collected from clinical information sheet associated with respiratory tract samples. RESULTS: Overall sensitivity for IgG was equivalent (around 80%) for CLIA, ELISA and LFIA. Sensitivity for IgG detection, >14 days after onset of symptoms, was 100.0% for all assays. Overall specificity for IgG was greater for CLIA and LFIA (more than 98%) compared to ELISA (95.8%). Specificity was significantly different between IgA ELISA (78.9%) and IgM LFIA (95.8%) (p < 0.05). The best agreement was observed between CLIA and LFIA assays (97%; k = 0.936). CONCLUSION: Excellent sensitivity for IgG detection was obtained >14 days after onset of symptoms for all immunoassays. Specificity was also excellent for IgG CLIA and IgG LFIA. Our study shows that NG-Test® is reliable and accurate for routine use in clinical laboratories.