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Monday, May 3, 2021

Fever Didn't Drive Many Americans to COVID Test

 Although fever is one of the classic symptoms of early COVID-19, most participants reporting febrile episodes in a large panel survey didn't get tested for the illness, researchers said.

Only 17% of people in the COVID-19 Citizen Science Study who self-reported temperatures higher than 38.0°C (100.4°F) at some point said they had been tested -- and nearly one-third of those hadn't received results within 2 weeks, according to Mark J. Pletcher, MD, MPH, of the University of California San Francisco (UCSF), and colleagues.

A statistical model bumped up that figure somewhat, with an estimated probability for receiving a coronavirus test result within 7 days of 20.5% (95% CI 19.1%-22.0%), reaching 26% by the end of 2 weeks (95% CI not given).

Black participants may have been even less likely to be tested, with an adjusted hazard ratio of 0.59 relative to non-Black/non-Hispanic participants, but this value was not statistically significant, the researchers reported in JAMA Network Open.

The data were based on a total of 3,865 febrile episodes reported by 2,679 participants.

"This cohort study's results suggest systematic underuse of coronavirus testing in patients with febrile illness," Pletcher and colleagues concluded. The findings also could explain why COVID-19 became a much bigger problem for the U.S. than it did in "countries such as China and South Korea," which pursued "a much more aggressive targeted approach to testing and appear to have substantially lower community transmission rates," the researchers wrote.

But why were rates in the Citizen Science Study so low? That remains a mystery.

"Whether this is because of lack of testing availability, knowledge about how to get a test, understanding about the importance of testing, or active avoidance (e.g., to avoid economic hardships associated with isolation and quarantine of contacts if one tests positive) is unclear," Pletcher and co-authors wrote.

Availability may have been a factor, especially early in the pandemic: in April 2020, only 9% of febrile participants said they had gotten a test, and it wasn't much higher in May. Moreover, fully one-third of them didn't receive a result within 2 weeks. By July, testing rates rose to 22% (P<0.001), and a somewhat higher proportion were receiving results. But these metrics didn't improve further through the rest of the study period.

The Citizen Science Study began in Mach 2020, run by UCSF and open to "any adult with a smartphone," according to a press release issued when the study began in March 2020. Participants were recruited by varied means, including advertisements and word of mouth, and thus could not be considered representative of the general population.

About three-quarters were women, but the sample did not skew heavily toward any age group; roughly 40% were 50 and older, and about the same percentage were younger than 40. The vast majority were white, however, with only 41 participants identifying as Hispanic and 183 as Black, preventing Pletcher's group from reaching many conclusions about racial/ethnic differences.

The requirement to be a smartphone user also tilted the sample toward higher socioeconomic status: about three-quarters rated their status as 6 or higher on the 10-point MacArthur scale. The researchers argued that this could mean the low testing rates in their study are actually an overestimate: "[T]his stratum of the U.S. population generally has better access to health care and resources than others, so if testing rates are low in our participants, they are likely even lower in more vulnerable subsets of the population," the team wrote.

Other limitations included that the data were based on unverified self-report, and that roughly 20% of participants reporting febrile episodes did not submit follow-up data on testing.

Disclosures

Pletcher reported no disclosures; one co-author reported owning Apple stock for a period prior to the conduct of the study.

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