Evaluation of Covid-19 antigen rapid diagnostic tests for self-testing in Lesotho and Zambia (preprint)

Background The use of antigen rapid tests (Ag-RDTs) for self-testing is an important element of the COVID-19 control strategy and has been widely supported. However, scale-up of self-testing for COVID-19 in sub-Saharan Africa is still insufficient and there is limited evidence on the acceptability of self-testing and agreement between Ag-RDT self-testing and Ag-RDT testing by professional users. A joint collaboration (BRCCH-EDCTP COVID-19 Initiative) was established between Lesotho and Zambia to address these gaps in relation to Ag-RDT self-testing and contribute to increasing its use in the region. Methods A cross-sectional study was conducted with qualitative and quantitative data analysis. Firstly, 11 in-depth cognitive interviews (5 in Zambia and 9 in Lesotho) were performed to assess the participants understanding of the instructions for use (IFU) for self-testing. In a second step, evaluation of test agreement between Ag-RDT self-testing and Ag-RDT testing by professional user using SD Biosensor STANDARD Q COVID-19 Ag-RDT was performed. In Zambia, usability and acceptability of self-testing were also assessed. Results Cognitive interviews in Lesotho and Zambia showed overall good understanding of IFU. In Zambia, acceptability of self-testing was high, though some participants had difficulties in conducting certain steps in the IFU correctly. Agreement between Ag-RDT self-test and Ag-RDT by professional users in Lesotho (428 participants) and Zambia (1136 participants) was high, 97.6% (404/414, 95% CI: 95.6-99.8) and 99.8% (1116/1118, 95% CI: 99.4-100) respectively. Conclusion Findings from this study support the use of Ag-RDT self-testing within COVID-19 control strategies in sub-Saharan Africa, contributing to increase the testing capacity and access in hard-to reach settings.

Impact of a multi-disease integrated screening and diagnostic model for COVID-19, TB, and HIV in Lesotho (preprint)

Introduction The surge of the COVID-19 pandemic challenged health services globally, and in Lesotho, the HIV and tuberculosis (TB) services were similarly affected. Integrated, multi-disease diagnostic services were proposed solutions to mitigate these disruptions. We describe and evaluate the effect of an integrated, hospital-based COVID-19, TB and HIV screening and diagnostic model in two rural districts in Lesotho, during the period between December 2020 and August 2022. Methods Adults and children above 5 years attending two hospitals were screened for COVID-19 and TB symptoms. After a positive screening, participants were offered to enroll in a service model that included clinical evaluation, chest radiography, SARS-CoV-2, Xpert MTB/RIF Ultra and HIV testing. Participants diagnosed with COVID-19, TB, or HIV were contacted after 28 days evaluate their health status, and linkage to HIV or TB services. Results Of the 179160 participants screened, 6623(37%) screened positive, and 4371(66%) were enrolled in this service model, yielding a total of 458 diagnoses. One positive rapid antigen test for SARS-CoV-2 was found per 11 participants screened, one Xpert-positive TB case was diagnosed per 85 people screened, and 1 new HIV diagnosis was done per 182 people screened. Of the 321(82.9%) participants contacted after 28 days of diagnosis, 304(94.7%) reported to be healthy. Of the individuals that were newly diagnosed with HIV or TB, 18/24(75.0%) and 46/51(90.1%) started treatment. This service showed no difference in the detection of new HIV and TB cases when compared to other hospitals, where no such integrated service model was provided. Conclusion This screening and diagnostic model successfully maintained same-day, integrated COVID-19, TB, and HIV testing services through different COVID-19 incidence periods in a resource-limited context. There were positive effects in avoiding diagnostic delays and ensuring linkage to services, however, efficiencies were contingent on the successful adaptation to the changing environment.

Head-to-head comparison of nasal and nasopharyngeal sampling using SARS-CoV-2 rapid antigen testing in Lesotho (preprint)

Objectives To assess the real-world diagnostic performance of nasal and nasopharyngeal swabs for SD Biosensor STANDARD Q COVID-19 Antigen Rapid Diagnostic Test (Ag-RDT). Methods Individuals [≥]5 years with COVID-19 compatible symptoms or history of exposure to SARS-CoV-2 presenting at hospitals in Lesotho received two nasopharyngeal and one nasal swab. Ag-RDT from nasal and nasopharyngeal swabs were performed as point-of-care on site, the second nasopharyngeal swab used for polymerase chain reaction (PCR) as the reference standard. Results Out of 2198 participants enrolled, 2131 had a valid PCR result (61% female, median age 41 years, 8% children), 84.5% were symptomatic. Overall PCR positivity rate was 5.8%. The sensitivity for nasopharyngeal, nasal, and combined nasal and nasopharyngeal Ag-RDT result was 70.2% (95%CI: 61.3-78.0), 67.3% (57.3-76.3) and 74.4% (65.5-82.0), respectively. The respective specificity was 97.9% (97.1-98.4), 97.9% (97.2-98.5) and 97.5% (96.7-98.2). For both sampling modalities, sensitivity was higher in participants with symptom duration [≤] 3days versus [≤] 7days. Agreement between nasal and nasopharyngeal Ag-RDT was 99.4%. Conclusions The STANDARD Q Ag-RDT showed high specificity. Sensitivity was, however, below the WHO recommended minimum requirement of [≥] 80%. The high agreement between nasal and nasopharyngeal sampling suggests that for Ag-RDT nasal sampling is a good alternative to nasopharyngeal sampling.

Diagnostic Accuracy of CAD4TB and C-reactive Protein Assay as Triage Tests for Pulmonary Tuberculosis