Study: Throat Swabs More Effective Than Nasal Swabs for COVID-19 Detection

A multicenter randomized clinical trial comparing the diagnostic accuracy of self- and health care worker (HCW)-collected nasal and throat swab specimens for COVID-19 rapid antigen testing found key differences in sensitivity. The study showed that HCW-collected throat swabs were more sensitive than nasal swabs for detecting SARS-CoV-2 via rapid antigen testing. However, among symptomatic individuals, self-collected nasal swabs proved to be more sensitive than self-collected throat swabs. The results suggest that incorporating throat swabs with nasal swabs could enhance the sensitivity of rapid antigen tests in both clinical and home settings.

This study was conducted to address ongoing debates over the best swab site for COVID-19 rapid antigen testing, given the reliance on nasal swabs despite uncertainties about their diagnostic accuracy. Previous studies had primarily focused on nasal swabs, leaving a gap in understanding the potential contribution of throat swabs in improving test sensitivity.

Researchers performed the study between February and March 2022 at two urban outpatient centers in Copenhagen, Denmark. The study included 2674 participants, who were randomized 1:1 to either self-collected or HCW-collected nasal and throat swabs, with reverse transcriptase-polymerase chain reaction (RT-PCR) used as the reference standard. The primary outcome was the sensitivity of the rapid antigen tests for detecting COVID-19, comparing nasal versus throat swabs in both self- and HCW-collected samples.

In the final analysis, 827 participants (30.9%) tested positive for SARS-CoV-2 by RT-PCR. HCW-collected throat swabs had a sensitivity of 69.4% (95% CI, 65.1%-73.6%) compared with 60.0% (95% CI, 55.4%-64.5%) for nasal swabs. However, in symptomatic participants, self-collected nasal swabs had a significantly higher sensitivity than self-collected throat swabs (71.5% [95% CI, 65.3%-77.6%] vs 58.0% [95% CI, 51.2%-64.7%]; P < .001). Additionally, combining both nasal and throat specimens increased sensitivity by 21.4% for HCW-collected samples and by 15.5% for self-collected samples, both statistically significant (P < .001).

Despite its robust design, the study has limitations. One major limitation is that it was conducted in a single city with participants self-selecting for COVID-19 testing, which could introduce selection bias. Furthermore, the performance of rapid antigen tests might differ with other SARS-CoV-2 variants or in populations with different symptom profiles.

 “Adding a throat specimen to the standard practice of collecting a single nasal specimen could improve sensitivity for rapid antigen testing in health care and home-based settings,” the study authors conclude.

Reference:

Todsen T, Jakobsen KK, Grønlund MP, et al. COVID-19 rapid antigen tests with self-collected vs health care worker-collected nasal and throat swab speciens. JAMA Netw Open. 2023;6(12). doi:10.1001/jamanetworkopen.2023.44295.