Prevalence of anti-SARS-CoV-2 IgG antibodies in a group of patients, a control group, and healthcare workers of Thrace area in Greece, by the use of two distinct methods

Theocharis Konstantinidis; Stavroula Zisaki; Ioannis Mitroulis; Dimitrios Cassimos; Ioanna Nanousi; Eftychia G Kontekaki; Vasilis Petrakis; Kalliopi Parrisi; Eleni Fotiadou; Aikaterini Linardou; Nikolaos Lemonakis; Anastasia Grapsa; Theodora Gioka; Leonidas Lazidis; Charalampos Papagoras; Chistina Tsigalou; Periklis Panagopoulos; Panagiotis Skendros; Georges Martinis; Maria Panopoulou

doi:10.18683/germs.2021.1274

Prevalence of anti-SARS-CoV-2 IgG antibodies in a group of patients, a control group, and healthcare workers of Thrace area in Greece, by the use of two distinct methods

Germs. 2021 Sep 29;11(3):372-380. doi: 10.18683/germs.2021.1274. eCollection 2021 Sep.

Authors

Theocharis Konstantinidis¹, Stavroula Zisaki², Ioannis Mitroulis³, Dimitrios Cassimos⁴, Ioanna Nanousi², Eftychia G Kontekaki⁵, Vasilis Petrakis⁶, Kalliopi Parrisi⁷, Eleni Fotiadou⁸, Aikaterini Linardou⁷, Nikolaos Lemonakis⁹, Anastasia Grapsa¹⁰, Theodora Gioka¹⁰, Leonidas Lazidis⁵, Charalampos Papagoras¹¹, Chistina Tsigalou¹², Periklis Panagopoulos¹³, Panagiotis Skendros¹¹, Georges Martinis⁵, Maria Panopoulou¹⁴

Affiliations

¹ MD, PhD, Blood Transfusion Center, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece, Laboratory of Microbiology, Democritus University of Thrace, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.
² MSc, Blood Transfusion Center, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.
³ MD, PhD, First Department of Internal Medicine, Democritus University of Thrace, Dragana Campus, 68100 Alexandroupolis, Greece.
⁴ MD, PhD, Pediatric Department, Democritus University of Thrace, Dragana Campus, 68100 Alexandroupolis, Greece, Alexandroupolis.
⁵ MD, Blood Transfusion Center, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.
⁶ MD, Second Department of Internal Medicine, Democritus University of Thrace, Dragana Campus, 68100 Alexandroupolis, Greece, Alexandroupolis.
⁷ Ms, Blood Transfusion Center, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.
⁸ Ms, Laboratory of Microbiology, Democritus University of Thrace, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.
⁹ MSs, Laboratory of Microbiology, Democritus University of Thrace, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.
¹⁰ MD, Laboratory of Microbiology, Democritus University of Thrace, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.
¹¹ MD, PhD, First Department of Internal Medicine, Democritus University of Thrace, Dragana Campus, 68100 Alexandroupolis, Greece, Alexandroupolis.
¹² MD, PhD, Laboratory of Microbiology, Democritus University of Thrace, University General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.
¹³ MD, PhD, Second Department of Internal Medicine, Democritus University of Thrace, Dragana Campus, 68100 Alexandroupolis, Greece, Alexandroupolis.
¹⁴ MD, PhD, Laboratory of Microbiology, Democritus University of Thrace, Universit y General Hospital of Alexandroupolis Dragana Campus, 68100 Alexandroupolis, Greece.

Abstract

Introduction: The aim of this study was to assess the clinical performance of different automated immunoassays available in Europe to detect anti-SARS-CoV-2 antibodies; an ELISA assay and a CLIA. The second goal was to estimate the seroprevalence of SARS-CoV-2 antibodies among healthcare workers in Evros area during the first pandemic wave of COVID-19.

Methods: The study included serum samples from 101 patients with confirmed COVID-19 by RT-PCR and 208 negative patients. Furthermore, it included 1036 healthcare workers (HWs) of the Evros Region, Northern Greece. The measurement of anti-SARS-CoV-2 antibodies was performed using the Abbott SARS-CoV-2 IgG and anti-SARS-CoV-2 ELISA IgG assay (Epitope Diagnostics, USA).

Results: Of 101 confirmed COVID-19 patients, 82 were hospitalized and 19 were outpatients. Hospitalized patients had higher IgG levels in comparison to outpatients (6.46±2.2 vs. 3.52±1.52, p<0.001). Of 208 non-COVID-19 patients only 1 was positive in both ELISA and CLIA assay. SARS-CoV-2-IgG antibodies were detected in 6 HWs out of 1036 (0.58%) with mean S/CO-value of anti-SARS-CoV-2 IgG 3.12±1.3 (confidence interval 0.95), which was lower than in COVID-19 patients (3.12 vs. 5.9; p=0.016). The clinical evaluation of two immunoassays showed remarkably high true positivity rates in the confirmed COVID-19 patients. Sensitivities obtained with CLIA and ELISA methods were 99.02% vs. 97.09% and specificities 99.52% vs 99.05% respectively.

Conclusions: We found an acceptable accordance between CLIA and ELISA assays in the confirmed COVID-19 patients. In all subjects included in this study in the past medical history, the information that was obtained included details about the presence of autoimmune diseases.

Keywords: COVID-19; RT-PCR; SARS-CoV-2; anti-SARS-CoV-2 antibodies; diagnosis; global health problem.

GERMS.