A prospective diagnostic evaluation of accuracy of self-taken and healthcare worker-taken swabs for rapid COVID-19 testing
Authors: Savage Helen R. , Finch Lorna , Body Richard , Watkins Rachel L. ,   LSTM Diagnostics group,   CONDOR steering group, Hayward Gail , Cook Eloïse , Cubas-Atienzar Ana I , Cuevas Luis E. , MacPherson Peter , Adams Emily R. 
Published: December 2021

Objectives

To compare self-taken and healthcare worker (HCW)-taken throat/nasal swabs to perform rapid diagnostic tests (RDT) for SARS-CoV-2, and how these compare to RT-PCR. We hypothesised that self-taken samples are non-inferior for use with RDTs and in clinical and research settings could have substantial individual and public health benefit.

Design

A prospective diagnostic accuracy evaluation as part of the ‘Facilitating Accelerated Clinical Evaluation of Novel Diagnostic Tests for COVID -19 (FALCON C-19), workstream C (undifferentiated community testing)’.

Setting

NHS Test and Trace drive-through community PCR testing site (Liverpool, UK). Participants

Eligible participants 18 years or older with symptoms of COVID-19. 250 participants recruited; one withdrew before analysis.

Sampling

Self-administered throat/nasal swab for the Covios® RDT, a trained HCW taken throat/nasal sample for PCR and HCW comparison throat/nasal swab for RDT.

Main outcome measures

Sensitivity, specificity, and positive and negative predictive values (PPV, NPV) were calculated; comparisons between self-taken and HCW-taken samples used McNemar’s test.

Results

Seventy-five participants (75/249, 30.1%) were positive by RT-PCR. RDTs with self-taken swabs had a sensitivity of 90.5% (67/74, 95% CI: 83.9-97.2), compared to 78.4% (58/74, 95% CI: 69.0-87.8) for HCW-taken swabs (absolute difference 12.2%, 95% CI: 4.7-19.6, p=0.003). Specificity for self-taken swabs was 99.4% (173/174, 95% CI: 98.3-100.0), versus 98.9% (172/174, 95% CI: 97.3-100.0) for HCW-taken swabs (absolute difference 0.6%, 95% CI: 0.5-1.7, p=0.317). The PPV of self-taken RDTs (98.5%, 67/68, 95% CI: 95.7-100.0) and HCW-taken RDTs (96.7%, 58/60, 95% CI 92.1-100.0) were not significantly different (p=0.262). However, the NPV of self-taken swab RDTs was significantly higher (96.1%, 173/180, 95% CI: 93.2-98.9) than HCW-taken RDTs (91.5%, 172/188, 95% CI 87.5-95.5, p=0.003).

Conclusion

Self-taken swabs for COVID-19 testing offer substantial individual benefits in terms of convenience, accuracy, and reduced risk of transmitting infection. Our results demonstrate that self-taken throat/nasal samples can be used by lay individuals as part of rapid testing programmes for symptomatic adults.

Trial Registration

IRAS ID:28422, clinical trial ID: NCT04408170

What is already known on this topic?

Rapid diagnostic tests (RDTs)for SARS-CoV-2 Ag are a cheaper point-of-care alternative to RT-PCR for diagnosing COVID-19 disease.

The accuracy of tests can vary dependent on sampling technique, test processing and reading of results.

What this study adds?

Self-taken throat-nasal swabs for RDTs can be used by symptomatic adults to give reliable results to diagnose SARS-CoV-2.

Self-sampling can be implemented with little training and no assistance.