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 chemiluminescence 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 agreement 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.
Subject(s)
Antibodies, Viral/blood , Coronavirus Infections/diagnosis , Coronavirus/isolation & purification , Pneumonia, Viral/diagnosis , Adolescent , Adult , Betacoronavirus , COVID-19 , Coronavirus/genetics , Coronavirus/immunology , Coronavirus Infections/epidemiology , Cross-Sectional Studies , Female , Humans , Luminescence , Male , Middle Aged , Pakistan/epidemiology , Pandemics , Pneumonia, Viral/epidemiology , Real-Time Polymerase Chain Reaction , Risk Factors , SARS-CoV-2 , SeroconversionABSTRACT
OBJECTIVE: To find out the sero-prevalence of COVID-19 IgG antibodies among policemen performing duties at high risk areas of Lahore, Pakistan. STUDY DESIGN: Cross-sectional, observational study. PLACE AND DURATION OF STUDY: Chughtai Lab Lahore from 20th to 30th May 2020. METHODOLOGY: One hundred and fifty-four young policemen (mean age 27.1 ±3.8 years) were included in the study after written consent. Squad officers who had any sign of acute respiratory infection were excluded from the study. The participants were asked to fill a questionnaire regarding nature of exposure with the infected cases, kind of personal protective equipment they are provided with and living arrangements. Three ml of blood samples were collected from the participants and immediately sent to the lab for analysis. COVID-19 IgG antibodies were analysed using chemiluminescence immunoassay method on Architect Ci8200 (Abbott). SPSS 23.0 was used for data analysis. RESULTS: All participants were males and mean age was 27.1 ±3.8 years. Out of 154 squad members, 24 were reactive for COVID-19 IgG antibodies and performing duties at the areas of high virus exposure. None of COVID-19 IgG reactive cases exhibited symptoms and most of them performed duties at high risk areas with only masks provided as personal protective equipment. Only 10% of the participants who were exposed to confirmed cases of COVID-19 were found to have anti-COVID IgG. CONCLUSION: COVID-19 IgG antibody reactive cases may not show any symptoms. Police force is at high risk of exposure. Serosurveys can help to find the spread of infection in the community and aid in planning healthcare strategies. Key Words: COVID-19, SARS CoV-2, Seroprevalence, Pandemic, Asymptomatic cases.