How have home testing kits affected official reporting of COVID-19 cases in the US?

By Neha MathurJan 30 2023Reviewed by Aimee Molineux

In a recent study published in JAMA Network Open, researchers gathered patients' self-reported data about the coronavirus disease 2019 (COVID-19) pandemic from across the United States of America (USA).

The COVID-19 Citizen Science Study, a cohort study, was launched in March 2020 and followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.

Background

The physical sites of COVID-19 testing reported severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test results to public health departments. This data helped detect a rise in SARS-CoV-2 transmission. During the COVID-19 pandemic, it emerged as a necessary exercise to intervene timely and reduce SARS-CoV-2 transmission.

However, the increasing availability of home-based COVID-19 rapid antigen tests (RAT) made it challenging to interpret temporal trends in officially reported COVID-19 case numbers based on the number of positive tests.

About the study

In the present study, researchers first invited people via social media, email, phone, or patient portal messaging via their recruitment partners. They enrolled 102,591 people who readily gave their demographic data and informed consent.

While patients self-reported their race and ethnicity, the research team specifically inquired about their most recent COVID-19 testing and its outcome each week throughout the study. It helped the researchers understand the differences in unreported COVID-19 test frequency and whether or not those were positive. After two years into the study, in March 2022, the researchers added a new question that helped them distinguish at-home and clinical SARS-CoV-2 tests.

On August 15, 2022, the researchers also retrieved data from the Johns Hopkins coronavirus resource center, representing nationwide SARS-CoV-2 testing data. They used it to plot seven-day moving averages of the cumulative number of daily COVID-19 tests and test positivity.

Finally, the team fitted a fixed effects model for the participant's demographic and time-related characteristics with study data. Likewise, they fitted a mixed logistic model with study data using a random intercept.

Results and conclusion

Of all the study participants, only 18% self-reported completing at least one SARS-CoV-2 test between March 16, 2022, and August 15, 2022. The researchers had complete demographic information of 18,546 participants, of which 67.8% were female. Most participants (82.1%) were non-Hispanic White, with an average age of 55.

The researchers observed that COVID-19 home testing became increasingly common, and by the summer of 2022, these tests made up 80% of all reported SARS-CoV-2 testing. In the beginning, COVID-19 home test data aligned well with national data of all reported COVID-19 tests. However, this pattern diverged soon, with home testing patterns starting to vary with demographics, perhaps because of varying levels of COVID-19 anxiety in different subpopulations, also based on the cost and availability of home test kits.

To conclude, the study findings confirmed that official COVID-19 case numbers underestimated the number of actual COVID-19 cases over time. It happened because earlier officially reported tests also reflected home test positivity, but this was not the case later.