Combination of a SARS-CoV-2 IgG Assay and RT-PCR for Improved COVID-19 Diagnosis

• Published in: Annals of laboratory medicine Vol. 41; no. 6; pp. 568 - 576
• Main Authors: Aoki, Kotaro, Takai, Kunitomo, Nagasawa, Tatsuya, Kashiwagi, Katsuhito, Mori, Nobuaki, Matsubayashi, Keiji, Satake, Masahiro, Tanaka, Ippei, Kodama, Nanae, Shimodaira, Takahiro, Ishii, Yoshikazu, Miyazaki, Taito, Ishii, Toshiaki, Morita, Toshisuke, Yoshimura, Toru, Tateda, Kazuhiro
• Format: Journal Article
• Language: English
• Published: Korea (South) Korean Society for Laboratory Medicine 01.11.2021; 대한진단검사의학회
• Subjects: Antibodies, Viral - analysis; COVID-19 - diagnosis; COVID-19 - virology; COVID-19 Testing; Humans; Immunoglobulin G - analysis; Longitudinal Studies; Original; Reagent Kits, Diagnostic; Retrospective Studies; Reverse Transcriptase Polymerase Chain Reaction; RNA, Viral - analysis; RNA, Viral - metabolism; SARS-CoV-2 - genetics; SARS-CoV-2 - immunology; SARS-CoV-2 - isolation & purification; Sensitivity and Specificity; 병리학; COVID-19; Immunoassay; Sensitivity; Specificity; Reverse transcription (RT)-PCR; SARS-CoV-2 IgG; ARCHITECT
• ISSN: 2234-3806; 2234-3814
• DOI: 10.3343/alm.2021.41.6.568

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is generally diagnosed by reverse transcription (RT)-PCR or serological assays. The SARS-CoV-2 viral load decreases a few days after symptom onset. Thus, the RT-PCR sensitivity peaks at three days after symptom onset (approximately 80%). We evaluated the performance of the ARCHITECT SARS-CoV-2 IgG assay (henceforth termed IgG assay; Abbott Laboratories, Lake County, IL, USA), and the combination of RT-PCR and the IgG assay for COVID-19 diagnosis. In this retrospective study, 206 samples from 70 COVID-19 cases at two hospitals in Tokyo that were positive using RT-PCR were used to analyze the diagnostic sensitivity. RT-PCR-negative (N=166), COVID-19-unrelated (N=418), and Japanese Red Cross Society (N=100) samples were used to evaluate specificity. Sensitivity increased daily after symptom onset and exceeded 84.4% after 10 days. Specificity ranged from 98.2% to 100% for samples from the three case groups. Seroconversion was confirmed from 9 to 20 days after symptom onset in 18 out of 32 COVID-19 cases with multiple samples and from another case with a positive result in the IgG assay for the first available sample. The combination of RT-PCR and IgG assay improves the robustness of laboratory diagnostics by compensating for the limitations of each method.