Population-based repeat cross-sectional seroprevalence survey of SARS-CoV-2 IgG antibodies in Pimpri Chinchwad Municipal Corporation Area, Maharashtra, India.

Context: Population-based seroepidemiological studies are recommended to measure the extent of spread of coronavirus disease of 2019 (COVID-19) infection in an area. The present seroprevalence survey was planned with the aim to estimate the cumulative burden of the COVID-19 disease in the Pimpri Chinchwad corporation area. Aims: To estimate the cumulative burden of the COVID-19 disease in the Pimpri Chinchwad corporation area. Settings and Design: The study was carried out in Pimpri Chinchwad Municipal Corporation (PCMC) city area. It was a descriptive cross-sectional survey. Materials and Methods: A population-based seroprevalence study for immunoglobulin G (IgG) antibodies for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was carried out among 10082 residents in the age group of 6 years and above selected by cluster random sampling. Thirty-five clusters were in slums, 45 clusters in tenements and 120 clusters from housing societies. The fieldwork for the collection of samples was carried out from 16 June to 17 June 2021. For antibody testing, a kit from Abbott (SARS-CoV-2 IgG) was used which employs chemiluminescent microparticle immunoassay (CMIA) technology. Statistical Analysis Used: Frequency analysis was done for sociodemographic variables, the cumulative incidence of COVID-19, age-stratified infection rate, risk factors and COVID symptomatic versus asymptomatic cases. Chi-square test of association was applied to test the association between seropositivity and sociodemographic and clinical profile of participants. Results: The overall seropositivity for IgG antibodies was 81.34%. Those living in the Gaothan area (tenements) had a positivity rate of 84.5%. The age group between 45 and 60 years had a seropositivity of 91%. Conclusions: The study indicates that a considerable proportion of the population had encountered the novel coronavirus approaching herd immunity.

Diagnostic performance of patient self-collected oral swab (tongue and cheek) in comparison with healthcare worker-collected nasopharyngeal swab for severe acute respiratory syndrome coronavirus-2 detection.

The present study was conducted to compare the performance of patient self-collected oral swab (OS) with healthcare worker (HCW)-collected nasopharyngeal swab (NPS) for SARS-CoV-2 detection by reverse transcription polymerase chain reaction (RT-PCR) in real-world setting. Paired OS and NPS were collected from 485 consecutive individuals presenting with symptoms of coronavirus disease-19 (COVID-19) or asymptomatic contacts of COVID-19 cases. Both specimens were processed for RT-PCR and cycle threshold (Ct) value for each test was obtained. Positive percent agreement (PPA), negative percent agreement (NPA), overall percent agreement (OPA) and kappa were calculated for OS RT-PCR compared with NPS RT-PCR as reference. A total of 116/485 (23.9%) participants were positive by NPS RT-PCR. OS had PPA of 71.6%, NPA of 98.8%, OPA of 92.4% and kappa of 0.771. Almost all participants (483/485, 99.6%) reported OS as a convenient and comfortable sample for SARS-CoV-2 testing over NPS. All participants with Ct values <25 and majority (90.8%) with Ct values <30 were detected by OS. To conclude, OS self-sampling was preferred in comparison with NPS due the ease and comfort during collection. The performance of OS RT-PCR for SARS-CoV-2 detection, however, was sub-optimal in comparison with NPS RT-PCR.

Diagnostic performance of oral swab specimen for SARS-CoV-2 detection with rapid point-of-care lateral flow antigen test.

We evaluated the performance of oral swab specimen both health-care worker (HCW) collected and self-collected for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) detection with rapid antigen test (RAT) as compared to reverse transcriptase polymerase chain reaction (RT-PCR). Of the 529 participants enrolled, 121 (22.8%) were RT-PCR positive. Among the RT-PCR positives, 62 (51.2%) were RAT positive using oral swab. When compared with RT-PCR, RAT with oral swab had sensitivity and specificity of 63.3 and 96.8% respectively among symptomatic individuals. No statistically significant difference was observed in RAT positivity with HCW collection and self-collection, p = 0.606. Ct values were significantly lower in RT-PCR and RAT positive samples (ORF gene: 18.85 ± 4.36; E gene: 18.72 ± 4.84) as compared to RT-PCR positive and RAT negative samples (ORF gene: 26.98 ± 7.09; E gene: 26.97 ± 7.07), p < 0.0001. Our study demonstrated moderate sensitivity of RAT with oral swab in symptomatic individuals. Oral swab was the preferred sampling by almost all participants in terms of convenience and comfort as compared to nasopharyngeal swab. Oral swabs have utility for SARS-CoV-2 antigen detection among symptomatic individuals residing in remote rural areas and can serve as an initial screening tool during COVID-19 spikes when cases rise exponentially and laboratory capacities for RT-PCR testing become overwhelmed.