Real-time reverse-transcriptase PCR (RT-PCR) has remained as the mainstay of testing for early detection of the virus among exposed and suspected patients.1 Many have raised questions on the roles of antibody testing in detecting patients with the disease. With a continuous clinical suspicion of COVID-19 and the second nucleic acid testing is still negative, two-point serum collection for antibody detection with (semi)quantitative serological assay in acute phase and 2-4 weeks later can be collected.2 The most sensitive and earliest serological marker is total antibodies, levels of which begin to increase from the second week of symptom onset.3 Although IgM and IgG ELISA have been found to be positive even as early as the fourth day after symptom onset, higher levels occur in the second and third week of illness.4 The presence of antibodies was <40% among patients within 1-week since onset, and rapidly increased to 94.3% (IgM) and 79.8% (IgG) since day-15 after onset.5 Institute for Medical Research (IMR) is one of the reference laboratories responsible for the COVID-19 test kits evaluation including the antibody tests for COVID-19. Flow Chart for Laboratory Diagnosis of SARS-CoV-2 in Suspected Case of COVID-19 Admitted to the Hospital, COVID-19 Management Guidelines in Malaysia No.5 / 2020 (Latest Update on 05 OGOS 2021) (https://covid-19.moh.gov.my/garis-panduan/garis-panduan-kkm/Annex_5c_edited_11112020.pdf)
Performance of selected SARS-CoV-2 antibodies immunoassays