Diagnosis of SARS-CoV-2 infection

Abstract

The most important use of serology in the COVID-19 diagnostics is for determination of the extent of disease in the population . However, immunoassays could represent an additional diagnostic method, especially in patients with exposure history and clinical symptoms compatible with COVID-19 who failed to be confirmed by RT-PCR. We analyzed the preliminary results of six serology tests for the diagnosis of SARS-CoV-2. Three point-of-care lateral flow chromatographic immunoassays (POC): ACRO, AMP and ENCODE and three enzyme immunoassays (ELISA): DiaPro, Vircell and Euroimmun were used. A total of 15 serum samples from COVID-19 patients and 15 serum samples from asymptomatic persons were tested. Time of sampling for COVID-19 patients was 4 – 10 days (N=4), 11 – 19 days (N=6) and 20 – 34 days (N=5) after disease onset. Initially reactive results were confirmed using a virus neutralization test (VNT). In COVID-19 patients (N=15), IgM/IgA positive detection rates were 9/60.0% (ACRO), 11/73.3% (AMP, ENCODE, Euroimmun), 12/80.0% (DiaPro) and 13/86.6% (Vircell). Overall IgG detection rates were 10//66.6% (AMP, Euroimmun) and 11/73.3% (other tests). According to the sampling time, positive detection rates were as follows: a) days 4 – 10: 1/25.0% and 2/50.0% (IgM/IgA and IgG); b) days 11 –19: 4/66.6%-6/100% (IgM/IgA), 4/66.6% and 5/83.3% (IgG); c) days 20 – 34: 4/80.0% and 5/100% (IgM/IgA), 5/100% (IgG). One asymptomatic participant tested IgM/IgA positive using ACRO, DiaPro and Vircell was confirmed seropositive using a VNT. In a group of asymptomatic persons detected seronegative using a VNT (N=14), IgM/IgA negative detection rates were 12/85.7% (ACRO), 13/92.8% (DiaPro, Vircell) and 14/100% (AMP, ENCODE, Euroimmun). IgG negative detection rates were 13/92.8% (ACRO) and 14/100% (other tests). ELISA tests showed a higher overall IgM/IgA sensitivity compared to POC tests in patients with COVID-19, while the IgG sensitivity was similar in both POC and ELISA. Najznačajnija primjena seroloških testova u dijagnostici COVID-19 je u svrhu procjene proširenosti bolesti u populaciji. Međutim, imunotestovi mogu poslužiti kao dodatni dijagnostički postupak, posebice kod bolesnika s podatkom o izloženosti COVID-19 i prisutnim kliničkim simptomima, kod kojih je rezultat RT-PCR testa bio negativan. U ovome smo radu analizirali preliminarne rezultate šest seroloških testova za dijagnostiku SARS-CoV-2. Korištena su tri 'point-of care' imunokromatografska testa (POC): ACRO, AMP i ENCODE te tri imunoenzimska testa (DiaPro, Vircell i Euroimmun). Testirano je ukupno 15 uzoraka seruma bolesnika s COVID-19 infekcijom i 15 uzoraka seruma asimptomatskih osoba. Vrijeme uzorkovanja kod bolesnika s COVID-19 iznosilo je 4 – 10 dana (N=4), 11 – 19 dana (N=6) te 20 – 34 dana (N=5) od početka bolesti. Svi su početno reaktivni rezultati potvrđeni testom neutralizacije virusa (VNT). Kod bolesnika s COVID-19 (N=15), učestalost detekcije IgM/IgA protutijela iznosila je 9/60,0% (ACRO), 11/73,3% (AMP, ENCODE, Euroimmun), 12/80,0% (DiaPro) te 13/86,6% (Vircell). Učestalost detekcije IgG protutijela iznosila je 10/66,6% (AMP, Euroimmun) te 11/73,3% (ostali testovi). Ovisno o vremenu uzorkovanja, učestalost detekcije protutijela iznosila je: a) 4-10. dana: 1/25,0% i 2/50,0% (IgM/IgA i IgG); b) 11-19. dana: 4/66,6%-6/100% (IgM/IgA), 4/66,6% i 5/83,3% (IgG; c) 20-34. dana: 4/80,0% i 5/100% (IgM/IgA), 5/100% (IgG). U jedne asimptomatske osobe s dokazanim IgM/IgA protutijelima testom ACRO, DiaPro i Vircell potvrđena su neutralizacijska protutijela. U skupini seronegativnih asimptomatskih osoba dokazanih VNT testom (N=14), negativan nalaz IgM/IgA je nađen u 12/85,7% (ACRO), 13/92,8% (DiaPro, Vircell) i 14/100% (AMP, ENCODE, Euroimmun) uzoraka, dok je negativan nalaz IgG dokazan kod 13/92,8% (ACRO) te 14/100% (ostali testovi) uzoraka. ELISA testovi pokazali su višu osjetljivost detekcije IgM/IgA protutijela u usporedbi s POC testovima, dok je osjetljivost detekcije IgG protutijela bila podjednaka u POC i ELISA testovima.