Rapid Antigen Tests Associated With Effective Sensitivity During Omicron Outbreak

Compared to polymerase chain reaction (PCR) testing, the sensitivity of rapid antigen testing for COVID-19 was not significantly associated with the amount of time between testing and when the patient began showing symptoms, according to investigators who published a study in BMJ Open. The results showed that rapid antigen tests averaged a 0.63 sensitivity score compared to the sensitivity of the PCR test, and rapid antigen testing had a specificity of 0.998.

“The results indicated that the sensitivity of the rapid antigen test compared with the results of the PCR test was independent of the duration from infection to testing or the presence or absence of symptom onset,” wrote study authors in a recent article.

The rapid antigen test is the least sensitive COVID-19 testing method, although it is the most inexpensive and provides quicker results. Further, other research has found that the rapid antigen tests are not as sensitive to the Omicron variant as they are to prior variants, such as Delta, but studies are limited.

If a rapid antigen test is considered to have lower sensitivity, it could be less effective at identifying individuals with a high COVID-19 viral load who have shown no symptoms. It has further raised concerns about rapid antigen tests being effective to use for the general population.

Investigators conducted a retrospective observational study to compare the sensitivity and specificity between the rapid antigen and PCR tests, using data collected from 656 cases from members of the Japan Professional Football League. The investigative team evaluated the relationships between sensitivity and time between testing and symptom onset, along with therelationship between sensitivity and vaccine status.

The time it took for an individual to present symptoms of infection was not associated with antigen test sensitivity. This contrasts with prior findings, which showed an association betweenrapid antigen tests and lower sensitivity compared to PCR tests. The investigators postulated that the high testing sensitivity could stem from participants being taught how to perform the test correctly.

Despite the sensitivity of the antigen test being 0.63 compared to the PCR, its cost is a tenth of the cost of the PCR test, investigators explained. “The rapid antigen test can be [also] performed more frequently than the PCR test assuming the same financial resources and is therefore expected to be highly effective in controlling infection,” study authors wrote in the analysis.

Additionally, the sensitivity of rapid antigen tests was not associated with vaccination status or test type.

However, the study includes limitations, starting with limited information about individual characteristics related to sensitivity and specificity. Additionally, specificity may have been underestimated, as there was no analysis on the association between sensitive and sample type, and there was no information on a patients’ personal COVID-19 history or medical history.

“The results of our study, which showed that the sensitivity of the rapid antigen test compared with the PCR test was 0.63 (95% CI: 0.53 to 0.73), may be used in combination with a model analysis to provide the fundamental knowledge required to establish a highly effective and efficient testing system,” investigators wrote. “Future testing strategies are expected to be combined with further model evaluations to match the characteristics of the Omicron variant.”

Reference

Murakami M, Sato H, Irie T, et al. Sensitivity of rapid antigen tests for COVID-19 during the Omicron variant outbreak among players and staff members of the Japan Professional Football League and clubs: a retrospective observational study. BMJ Open. 2023;13:e067591. doi:10.1136/bmjopen-2022-067591