Diagnosis of COVID-19 by Serology in Admitted Patients with Negative  RT-PCR Assay

Mitra Rezaei; Parvaneh Baghaei; Makan Sadr; Afshin Moniri; Abdolreza Babamahmoodi; Somayeh Qadimi; Mihan Pourabdollah; Seyed Alireza Nadji; Payam Tabarsi; Majid Marjani

doi:10.18502/ijaai.v20i4.6949

Mitra Rezaei Virology Research Center, National Research Institute of Tuberculosis and Lung diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Parvaneh Baghaei Clinical Tuberculosis and Epidemiology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Makan Sadr Virology Research Center, National Research Institute of Tuberculosis and Lung diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Afshin Moniri Clinical Tuberculosis and Epidemiology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Abdolreza Babamahmoodi Clinical Tuberculosis and Epidemiology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Somayeh Qadimi Clinical Tuberculosis and Epidemiology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Mihan Pourabdollah Chronic Respiratory Disease Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Seyed Alireza Nadji Virology Research Center, National Research Institute of Tuberculosis and Lung diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Payam Tabarsi Clinical Tuberculosis and Epidemiology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
Majid Marjani Clinical Tuberculosis and Epidemiology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran

DOI: https://doi.org/10.18502/ijaai.v20i4.6949

Keywords: Antibodies; COVID-19; Diagnosis; Reverse transcription polymerase chain reaction; Serology

Abstract

Considering the increasing prevalence and burden of coronavirus disease 2019 (COVID-19) disease and false-negative results in routine reverse transcription-polymerase chain reaction (RT-PCR) tests, additional diagnostic methods are needed to diagnose active cases of this disease.

This prospective study was conducted on patients, in whom clinical and radiological symptoms/signs were in favor of COVID-19 while their first PCR test was negative. Later on, a second RT-PCR was performed and serological evaluation was carried out and results were compared with each other.

Out of 707 patients who had been referred to the hospital and were clinically and radiologically suspicious of disease, 137 patients with negative RT-PCR tests entered the study. RT-PCR assay became positive for the second time in 45 (32.8%). Anti-COVID-19 IgM and IgG antibodies were positive in 83 (60.6%) and 86 (62.8%) patients, respectively. Finally, it was determined that serological test was diagnostic in 73% of patients and the diagnostic yield of serology was significantly higher after the first week of illness (54.8% in the first week and 88% after that). Taking advantage of both serological tests and RT-PCR helps in diagnosing 83.9% of cases.

Based on the present study, the serology may be useful as a complementary test and in parallel to RT-PCR assay for diagnosis of COVID-19 among admitted symptomatic cases.