Factors Associated With Access to and Timing of Coronavirus Testing Among US Adults After Onset of Febrile Illness

Abstract

Importance: Active SARS-CoV-2 (coronavirus) transmission continues in the US. It is unclear whether better access to coronavirus testing and more consistent use of testing could substantially reduce transmission.

Objective: To describe coronavirus testing in persons with new onset of febrile illness and analyze whether there are changes over time and differences by race and ethnicity.

Design, setting, and participants: This cohort study used data from the COVID-19 Citizen Science Study, launched in March 2020, which recruited participants via press release, word-of-mouth, and partner organizations. Participants completed daily surveys about COVID-19 symptoms and weekly surveys about coronavirus testing. All adults (aged at least 18 years) with a smartphone were eligible to join. For this analysis, US participants with new onset of febrile illness from April 2020 to October 2020 were included. Data analysis was performed from November 2020 to March 2021.

Main outcomes and measures: Receipt of a coronavirus test result within 7 days of febrile illness onset.

Results: Of the 2679 participants included in this analysis, the mean (SD) age was 46.3 (13.4) years, 1983 were female (74%), 2017 were college educated (75%), and a total of 3865 distinct new febrile illness episodes were reported (300 episodes [7.8%] from Hispanic participants, 71 episodes [1.8%] from Black participants, and 3494 episodes [90.4%] from not Black, not Hispanic participants) between April 2 and October 23, 2020. In weekly surveys delivered during the 14 days after fever onset, 12% overall (753 participants) indicated receipt of a test result. Using serial survey responses and parametric time-to-event modeling, it was estimated that by 7 days after onset of febrile illness, a total of 20.5% (95% CI, 19.1%-22.0%) had received a test result. This proportion increased from 9.8% (95% CI, 7.5%-12.0%) early in the epidemic to 24.1% (95% CI, 21.5%-26.7%) at the end of July, but testing rates did not substantially improve since then, increasing to 25.9% (95% CI; 21.6%-30.3%) in late October at the start of the winter surge. Black participants reported receiving a test result about half as often as others (7% [7 of 103] of survey responses vs 12% [53 of 461] for Hispanic vs 13% [693 of 5516] for not Black, not Hispanic; P = .03). This association was not statistically significant in adjusted time-to-event models (hazard ratio = 0.59 vs not Black, not Hispanic participants; 95% CI, 0.26-1.34).

Conclusions and relevance: Systematic underuse of coronavirus testing was observed in this cohort study through late October 2020, at the beginning of the winter COVID-19 surge, which may have contributed to preventable coronavirus transmission.

Figure 1.. Self-reported Coronavirus Test Result Status as Reported by Participants With New Febrile Illness by Days Since Onset

Fitted probability represents the cumulative proportion with a coronavirus test result by days after onset of illness estimated with an unadjusted interval-censored Weibull model (see Methods section) using all survey responses. At 7 days after onset, the model estimated a cumulative proportion of 20.5% (95% CI, 19.1%-22.0%) (circular data marker). This overall result does not consider calendar date or other covariates.

Figure 2.. Proportion With a Coronavirus Test Result at 7 Days After Febrile Illness Onset, Over Calendar Time, by Race/Ethnicity

Proportions represent fitted cumulative hazard estimates from interval-censored Weibull models (see Methods section) that include date (fit as a cubic spline), with and without race/ethnicity also included (main effect and interactions with spline variables). On October 23, 2020 (the last episode date analyzed), the model estimated that overall 25.9% (95% CI, 21.6%-30.3%) of persons with a febrile illness will get a test result by 7 days after onset of their illness (circular data marker). With interactions included, estimates on October 23, 2020, were 5% (95% CI, −8% to 18%) for Black, not Hispanic participants; 20% (95% CI, 4%-36%) for Hispanic, not Black participants; and 27% (95% CI, 22%-31%) for participants who were not Hispanic or Black.