ABSTRACT
Background: Antibody testing is often used for serosurveillance of coronavirus disease 2019 (COVID-19). Enzyme-linked immunosorbent assay and chemiluminescence-based antibody tests are quite sensitive and specific for such serological testing. Rapid antibody tests against different antigens are developed and effectively used for this purpose. However, their diagnostic efficiency, especially in real-life hospital setting, needs to be evaluated. Thus, the present study was conducted in a dedicated COVID-19 hospital in New Delhi, India, to evaluate the diagnostic efficacy of a rapid antibody kit against the receptor-binding domain (RBD) of the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: Sixty COVID-19 confirmed cases by reverse transcriptase-polymerase chain reaction (RT-PCR) were recruited and categorized as early, intermediate, and late cases based on the days passed after their first RT-PCR-positive test report, with 20 subjects in each category. Twenty samples from pre-COVID era and 20 RT-PCR-negative collected during the study period were taken as controls. immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against the RBD of the spike (S) protein of SARS-CoV-2 virus were detected by rapid antibody test and compared with the total antibody against the nucleocapsid (N) antigen of SARS-CoV-2 by electrochemiluminescence-based immunoassay (ECLIA). Results: The detection of IgM against the RBD of the spike protein by rapid kit was less sensitive and less specific for the diagnosis of SARS-CoV-2 infection. However, diagnostic efficacy of IgG by rapid kit was highly sensitive and specific when compared with the total antibody against N antigen measured by ECLIA. Conclusion: It can be concluded that detection of IgM against the RBD of S protein by rapid kit is less effective, but IgG detection can be used as an effective diagnostic tool for SARS-CoV-2 infection in real-life hospital setting.
ABSTRACT
Obstructive Sleep Apnea Syndrome (OSAS) has been recognised as a major cause of morbidity and mortality in developing countries like India. There is still a paucity of Indian studies regarding the prevalence of OSAS. The current single centre prospective cross-sectional study was undertaken to know prevalence estimates for key symptoms and features that can indicate the presence of OSAS in an Indian population. A survey was conducted on subjects with age groups ≥ 25 years at King George's Medical University, Lucknow, Uttar Pradesh, India from August 2009 to July 2011. Data was recorded during the interview on the basis of Berlin Questionnaire (BQ). Risk factors for OSAS were also evaluated. Risk group categorization for OSAS was done with the help of a questionnaire and overnight polysomnography was performed in each group to measure apnea and hypopnea index (AHI). Out of 1816 subjects, 1512 (response rate 83.3%) finally participated in the survey with mean age 42.6±11.2 years, males 67.9% and females 32.1%. Of them 6.2% were found to be at high-risk OSAS; 12.2% were obese (Body Mass Index ≥30 kg/m2) and 33.5% of the obese population were at high-risk OSAS. Among high-risk patients with OSAS, 62.4% had hypertension. Statistically significant and independent risk factors found for OSAS were obesity, large neck size, alcoholism and use of sedatives/tranquillizers. High-risk category predicted an AHI ≥5 with a sensitivity of 86.3% (95% CI 73.1-93.8), specificity of 93.1% (95% CI 89.1-95.7), positive and negative predictive values of 70.9% (95% CI 57.9-81.4) and 97.2% (95% CI 94.1-98.8) respectively. It can be concluded that BQ questionnaire can still be used as a pre-assessment tool for predicting persons at risk for OSAS in clinical practice. Further studies on estimation of prevalence of OSAS by applying BQ are warranted in near future from other regions of India.
