Analysis of adjunctive serological detection to nucleic acid test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection diagnosis

Abstract

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused coronavirus disease 2019 (COVID-19) epidemic in China, December 2019. The clinical features and treatment of COVID-19 patients remain largely elusive. However, accurate detection is required for SARS-CoV-2 infection diagnosis. We aimed to evaluate the antibodies-based test and nucleic acid-based test for SARS-CoV-2-infected patients.

Methods: We retrospectively studied 133 patients diagnosed with SARS-CoV-2 and admitted to Renmin Hospital of Wuhan University, China, from January 23 to March 1, 2020. Demographic data, clinical records, laboratory tests, and outcomes were collected. Data were accessed by SARS-CoV-2 IgM-IgG antibody test and real-time reverse transcriptase PCR (RT-PCR) detection for SARS-CoV-2 nucleic acid in COVID-19 patients.

Results: Of 133 COVID-19 patients, there were 44 moderate cases, 52 severe cases, and 37 critical cases with no differences in gender and age among three subgroups. In RT-PCR detection, the positive rate was 65.9%, 71.2%, and 67.6% in moderate, severe, and critical cases, respectively. Whereas the positive rate of IgM/IgG antibody detection in patients was 79.5%/93.2%, 82.7%/100%, and 73.0%/97.3% in moderate, severe, and critical cases, respectively. Moreover, the IgM and IgG antibodies concentrations were also examined with no differences among three subgroups.

Conclusion: The IgM-IgG antibody test exhibited a useful adjunct to RT-PCR detection, and improved the accuracy in COVID-19 diagnosis regardless of the severity of illness, which provides an effective complement to the false-negative results from a nucleic acid test for SARS-CoV-2 infection diagnosis after onsets.

Keywords: COVID-19; IgM-IgG antibody test; Nucleic acid test; SARS-CoV-2; Severity of illness.

Fig. 1

The time features of nucleic acid test and IgM-IgG antibody test for COVID-19 patients. The graticule represents the panoramic timeline of onset of illness (blue grid), nucleic acid test (green grid), and IgM-IgG antibody test (red grid) of 133 patients infected with SARS-CoV-2. The interval of data from January 23, 2020, to March 1, 2020, was the period of hospitalization. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Nucleic acid and antibody tests in patients with COVID-19. (A) The histogram of frequency distribution reflects that 44.4% of patients were tested for nucleic acid and IgM-IgG antibody successively within a week, while 45.8% of patients were tested for IgM-IgG antibody after a week or even longer. The number in the horizontal axis indicated the interval days of IgM-IgG antibody test after nucleic acid test. (B) The histogram of frequency distribution of interval of IgM-IgG antibody test after onset of illness since January 1, 2020. 82.7% of patients were tested for IgM-IgG antibody during 14–35 days after onset, while 13.6% of patients were tested more than 35 days after onset, and 3.8% of patients were tested within 14 days after onset. (C) The distribution of cases number from results of different tests in COVID-19 diagnosis by three subsets, 1: RT-PCR and IgM, 2: RT-PCR and IgG, and 3: IgM and IgG. + and – stand for positive and negative results in the indicated tests, respectively. No., Number.