Efficacy of rapid antigen diagnostic tests for the detection of infectious individuals at mass gatherings

By Susha Cheriyedath, M.Sc.Jan 5 2022Reviewed by Aimee Molineux

A study recently posted in the medRxiv* preprint server explored the use of rapid antigen diagnostic tests (RADTs) to estimate the number of individuals infected with the coronavirus disease 2019 (COVID-19) at any particular event that might have a mass gathering of people.

Introduction

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

The usefulness of RADTs has been widely considered to be instrumental in controlling the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. However, despite being cheaper and easier to use, RADTs have lower specificity and sensitivity towards detecting the SARS-CoV-2 virus. With more research, RADTs can help reduce the spread of COVID-19 by testing individuals attending mass gatherings, either during or right before entering the venue.

About the study

In this study, the researchers investigated the applications of RADTs in testing populations for SARS-CoV-2 infections at the level of a social event. Mass gatherings of individuals of different age groups were simulated to estimate the number of infectious individuals. The incidence of individuals infected with the SARS-CoV-2 virus was then estimated to describe the number of infectious days in a particular age group of a population. The researchers noted that the number of infection days for each infected individual varies depending on whether or not they are tested positive, at what point in the infectious cycle are they detected, and if they restrict their exposure to others as per public health guidelines.

Researchers simulated the probable occurrence of infectious individuals within each age group for a given 14-day incidence of COVID-19 infection. They then simulated mass gatherings with individuals of different age groups to estimate the overall presence of infectious individuals at the event. The potential outcome of the tests was also simulated to showcase the diagnostic test sensitivity and specificity of the RADTs. This outcome was identified in terms of the number of true positives and negatives, the number of false positives and negatives, positive and negative predictive values, and the cost of detecting each case.

To allow and understand the proportions of infectious individuals attending a mass gathering, the researchers developed an application called RShiny that allows the users to estimate the number of COVID-19 infected individuals at an event.

Results

Infectious individuals belonging to the younger age groups were found to be more prevalent, at 1.00%, in mass gatherings. Homogeneous age gatherings at 0.55% were the next most prevalent. This was followed by a population of mostly older individuals accounting for 0.26% prevalence.

For events with around 100 attendees, the prevalent number of infectious attendees was less than or equal to one across all age groups in the population. In events consisting of younger individuals, the expected number of infectious individuals was 1.0 while for the ones with older individuals, it was 0.26. For events of 10,000 attendees, the expected number of infectious individuals was almost 100 for younger attendees and 26 for older attendees.

The characteristics of RADTs could mean that half of the test results can be false negative. The number of false negatives ranged from 0-1 for small mass gatherings including older individuals whereas the range of false negatives was 2-101 for larger mass gatherings. The number of false negatives for small gatherings including younger individuals was in the range 0-2. This range increased to 20-86 false negatives for larger gatherings including younger individuals.

Conclusion

The study findings show that incidence data often underestimates the prevalence of infectious individuals at a given point in time in a population. RADTs can help estimate a more likely number of people infected with COVID-19 in a particular mass gathering. The study demonstrates that infectious individuals are more prevalent in mass gatherings consisting mainly of younger people. Although the younger age group is at a lower risk of COVID-19 complications, infections in younger individuals can easily lead to an increased incidence in and transmission to older, high-risk communities.

Apart from being a tool to control the spread of the SARS-CoV-2RADTs also allow focused asymptomatic testing and asymptomatic testing to allow quarantine release, attendance of mass gatherings, or other restricted activities. Despite the differences in COVID-19 manifestations in different regions, RADTs can be used to control the spread of SARS-CoV-2 with further improvement and investigation, irrespective of geographical boundaries.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources