ORIGINAL ARTICLE Journal of the College of Physicians and Surgeons Pakistan 2020, Vol. 30(08): 801-804 801 Seroconversion in Newly Diagnosed Cases of Coronavirus Disease Omar Rasheed Chughtai 1 , Hijab Batool 2 , Muhammad Dilawar Khan 2 and Shakeel Ashraf 2 1 Department of Histopathology, Chughtai Institute of Pathology, Lahore, Pakistan 2 Department of Clinical Chemistry and Immunology, Chughtai Institute of Pathology, Lahore, Pakistan ABSTRACT Objective: To determine the percentage of seroconverted real time reverse transcriptase polymerase chain reaction (RT-PCR) positive coronavirus disease (COVID-19) cases at different days post-symptom onset; and also find the agreement of chemilumi- nescence assay used for total antibody detection using RT-PCR as a reference method. Study Design: Cross-sectional study. Place and Duration of Study: Chughtai Institute of Pathology from April to May 2020. Methodology: Fifty pre-pandemic samples (healthy population) and 75 COVID-19 patients were included in the study. RT-PCR confirmed COVID-19 patients were divided into 3 equal groups (25 each), according to the days of symptom onset. The samples were analysed using electro-chemiluminescence as assay principle. Positive and negative agreement of COVID-19 antibodies was calculated using EP evaluator to find out the sensitivity of chemiluminescence assay for total antibody detection. The results were analysed using SPSS version 23.0. Results: All the pre-pandemic samples tested were negative for antibodies with a negative agreement of 100%. Total agree- ment at day 7 post-symptom onset was 84%; whereas, it was 94% at day 14 and increased rapidly to 100% at day 21 post- symptom onset. At day 7 post-symptom onset, 68% of patients were seroconverted; and this percentage was 88% and 100% at day 14 and 21 post-symptom onset, respectively. Conclusion: Pre-pandemic samples were non-reactive for COVID-19 antibodies and seroconversion started within the first week post-virus exposure. There was 100% concordance between RT-PCR result and antibody positivity 21 days post-symptom onset. Key Words: COVID-19, SARS CoV-2, Seroconversion, Chemiluminescence . How to cite this article: Chughtai OR, Batool H, Khan MD, Ashraf S. Seroconversion in Newly Diagnosed Cases of Coronavirus Disease. J Coll Physicians Surg Pak 2020; 30(08):801-804. INTRODUCTION Twenty-seven mysterious cases of pneumonia were diag- nosed in China on December 31, 2019. The causative organism was identified with the help of swab test (throat or nasopharyngeal) at Disease Control and Prevention Center in themonthofJanuary2020. 1 WHOnamedthisdiseaseascoron- avirus disease (COVID-19) and the organism was named as SARS CoV-2 . 2 Mild symptoms like dry cough, fever and headache were present in many patients suffering from COVID-19; whereas, some of the cases remained asympto- maticandresolvedspontaneously. Correspondence to: Dr. Hijab Batool, Department of Clin- ical Chemistry and Immunology, Chughtai Institute of Pathology, Lahore, Pakistan E-mail: dr.hijabbatool@cll.edu.pk ..................................................... Received: May 29, 2020; Revised: July 17, 2020; Accepted: July 24, 2020 DOI: https://doi.org/10.29271/jcpsp.2020.08.801 On the other hand, some cases turned out with fatal complica- tionssuchasmultiorganfailure,sepsis,pneumonia,pulmonary edema and severe respiratory distress syndrome. 3 Uncertainty prevails regarding the mode of spread of this viral disease. According to the current knowledge, this virus is transmitted through respiratory fomites; and symptomatic patients are highly contagious. 4 On the other hand, asymptomatic patients can also spread virus in their incubation period. 5 Thepresentlyreportedfigurescanbeanunderestimationofthe disease in Pakistan as the data depicts laboratory confirmed diagnosed cases only. 6 The only strategy to disrupt the spread of COVID-19 in Pakistan is early and correct diagnosis, isolation ofinfectedcases,andtimelytreatment.Moreover,thereshould be a tracing system for close contacts of the infected cases. Numerous healthcare companies have developed testing metho- dologies to diagnose COVID-19 infection. The gold standard diag- nostic test available for COVID-19 is real time reverse transcrip- tasePCR(RT-PCR)havingthehighestsensitivityandspecificity. 7 It detects viral genome and is widely used for diagnosis, moni- toring disease spread, patient triage and current infection status. On the other hand, there are some serological tests also whichcommentontheimmunestatusofthepatient.Thesesero- logical tests assess the immune response of the individual