Clinical Performance of Self-Collected Nasal Swabs and Antigen Rapid Tests for SARS-CoV-2 Detection in Resource-Poor Settings

Abstract

Background: In resource-poor countries, antigen-based rapid tests (Ag-RDTs) performed at primary healthcare and community settings improved access to SARS-CoV-2 diagnostics. However, the technical skills and biosafety requirements inherent to nasopharyngeal and oropharyngeal (OP) specimens limit the scale-up of SARS-CoV-2 testing. The collection of nasal-swabs is programmatically viable, but its performance has not been evaluated in resource-poor settings. Methods: We first evaluated the performance of SteriPack self-collected nasal swabs for the detection of SARS-CoV-2 by real-time PCR in 1498 consecutively enrolled patients with suspected infection. Next, we evaluated the clinical performance of three nasal swab-based Ag-RDTs against real-time PCR on OP specimens. Results: The sensitivity of nasal swabs was 80.6% [95% CI: 75.3−85.2%] compared to OP specimens. There was a good correlation (r = 0.58; p < 0.0001) between Ct values of 213 positive cases obtained using nasal and OP swabs. Our findings show sensitivities of 79.7% [95% CI: 73.3−85.1%] for Panbio COVID-19 Ag-RDT, 59.6% [95% CI: 55.2−63.8%] for COVIOS Ag-RDT, and 78.0% [95% CI: 73.5−82.0%] for the LumiraDx SARS-CoV-2 Ag-RDT. Conclusions: In our setting, the COVIOS Ag-RDT did not meet WHO requirements. Nasal swab-based Ag-RDTs for SARS-CoV-2 detection constitute a viable and accurate diagnostic option in resource-poor settings.

Keywords: antigen rapid tests; clinical evaluation; nasal swabs; resource-poor settings; self-collection.

Figure 1

Correlation of Ct value of the positive cases (n = 213) in paired self-collected SteriPack nasal and oropharyngeal swab evaluation.