Determining the optimal frequency of SARS-CoV-2 regular asymptomatic testing: A randomized feasibility trial in a...

The SARS-CoV-2 pandemic presented a challenge for caregiving relatives in the home care setting. Caregivers can transmit SARS-CoV-2 to their relatives who are often at high risk for a severe course of COVID-19. Regular testing of asymptomatic caregivers for SARS-CoV-2 may reduce the risk of transmission. The optimal method and frequency of regular asymptomatic testing is unknown. We conducted a prospective, randomised trial to assess the feasibility, recruitment and acceptance of different testing frequencies. This serves to inform a future definitive randomised controlled trial.

We carried out a parallel three-armed feasibility trial, enrolling adult participants who provided home-based care for a relative at least twice a week. Participants were randomly assigned using sealed envelopes to either conduct saliva-based antigen self-testing at a frequency of once a week (group I), twice a week (group II), or every two days (group III). The participants completed questionnaires on a weekly basis. Main outcome measures were feasibility of recruitment, adherence to self-tests and distress caused by self-testing. We further collected data on the use of mouth-nose mask.

From 25 March to 7 May 2021 we assessed 27 participants and randomised 26 in the study: 8 participants in group I, 8 in group II and 10 in group III. All participants completed the study. In group I 48/48 (100.0%; 95% CI 92.6% to 100.0%), in group II 93/96 (96.9%; 95% CI 91.2% to 98.9%) and in group III 209/210 (99.5%; 95% CI 97.4% to 99.9%) self-tests were carried out at home. Participants did not perceive regular self-testing as burdensome in any of the study arms. We did not observe any infection with SARS-CoV-2. During the study, mask adherence decreased from 35% to 19% in all groups.

Conducting such a study was feasible. The participants tolerated regular self-testing well, which was reflected in a high level of test adherence. However, regular self-testing may have led to decreased protective behaviour. To demonstrate that regular asymptomatic testing reduces infection transmission, a future definitive trial should be performed at a time of a high prevalence of SARS-CoV-2 and be implemented as a multicentre study.

The trial is registered with the German Clinical Trials Register, DRKS00026234.