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Validation of an At-Home Direct Antigen Rapid Test for COVID-19

Our take —

This study evaluated the effectiveness of the at-home direct antigen rapid test (DART) for COVID-19 to compare performance with qRT-PCR on self-collected nasal specimens among employees within the Cambridge and Boston areas over a 6 month period. Surveillance using twice weekly testing with DART was 96.2% sensitive in identifying individuals positive for COVID-19 between 0-3 days of symptoms, compared to self-collected swabs that were tested by qRT-PCR. Although only laboratory affiliated persons were recruited and results may differ from within the general population as they may be better at self-swabbing, twice-weekly DART testing was able to identity positive participants before reported symptoms of COVID-19. This study shows real-world application to workplace surveillance to prevent in-person transmission in social environments.

Study design

Prospective Cohort

Study population and setting

Within a 6-month period (NB: exact dates of study recruitment and enrollment were not provided in the manuscript), 257 employees (age 21-72 years ) working at 3 laboratories in Cambridge and Boston, Massachusetts self-collected 2 nasal swab specimens twice weekly. Swabs were tested by direct antigen rapid tests (DARTs) and the gold standard qRT-PCR and results were compared. The DART cassette contains a monoclonal antibody/nanoparticle conjugate that detects the nucleocapsid protein in SARS-Co-V-2, displaying visible lines for positive and negative results. The DART test was completed at home, where the swab was mixed with an extraction buffer, then 100ul were measured and placed into the DART cartridge, before waiting 15 minutes before reading. The second swab was sent to the laboratory for qRT-PCR testing.

Summary of Main Findings

During the study period, 15 participants contracted COVID-19 as determined by self-swab qRT-PCR testing, and the twice weekly self-swabs tested by DART detected 100% of these infections. Between 0-12 days of symptom onset, as compared to qRT-PCR, the sensitivity of DART was 78.9% (95% CI, 69.1%-88.8%) and the specificity was 97.1% (95% CI 96.3-97.8%).  DART sensitivity for SARS-CoV-2 nucleocapsid and RNA detection for individual infections was 96.2% (95% CI 88.8%-100.0%) within 0-3 days of symptom onset.

Study Strengths

This was a prospective study where large number of samples were collected from a small cohort overtime. Paired self-collected nasal swabs were tested by DART and qRT-PCR. 

Limitations

Those enrolled in this study were affiliated with one of three laboratories, and no one from the general population was included. The ability of these participants to complete the DART test, which required pipetting reagents and sample, therefore, may have differed from that of the general population.

Value added

This study  validated effectiveness of at-home DART testing. This was the first time a direct comparison of self-collected rapid testing compared to self-collected swabs for qRT-PCR testing used in workplace surveillance.

This review was posted on: 2 November 2021