U.K. and U.S. residents who reported a loss of smell and taste into a COVID-19 symptom-tracker app more often tested positive for the infection, according to a study published yesterday in Nature.

The COVID Symptom Study app was developed by health technology company Zoe Global with help from King's College London and Massachusetts General Hospital. It launched in the U.K. and the U.S. in late March, and after three weeks had gained more than 2.6 million users.

By applying a predictive model incorporating these testing rates to the hundreds of thousands of users who reported symptoms without testing data, the researchers estimated that a little over 5% of those who downloaded the app "are likely to have COVID-19." However, the researchers cautioned that this is likely an overestimation due to a handful of factors, such as the use of self-reported symptom data.

TOPLINE RESULTS

A total of 2,6618,862 residents from the U.K. (n = 2,450,569) and U.S. (n =168,293) downloaded the free study app and reported potential COVID-19 symptoms. Of these, 15,638 from the U.K. and 2,763 from the U.S. paired their reported symptoms with the results of a RT-PCR SARS-CoV-2 test.

Among the U.K. cohort, nearly two thirds of those who reported positive test results also reported a loss of smell and taste, compared to the roughly 23% of negative cases who reported the same symptoms, yielding an odds ratio [OR] of 6.4 (p < .0001). Combining these rates with the U.S. cohort's OR of 10.01 (p < .0001) produced an overall OR of 6.74 (P < .0001) after adjustments.

"We report that loss of smell and taste is a potential predictor of COVID-19 in addition to other, more established symptoms including high temperature and a new, persistent cough," the researchers wrote. "COVID-19 appears to cause problems of smell receptors in line with many other respiratory viruses, including previous coronaviruses thought to account for 10%–15% of cases of anosmia."

The analysis also found 10 other symptoms such as fever, fatigue, shortness of breath and diarrhea to be associated with positive diagnostic test among the U.K. cohort, while only loss of smell and taste, fatigue and skipped meals were associated among the U.S. cohort.

From these findings, the researchers build a symptoms-prediction model to estimate the number of untested participants (n = 805,753) who likely had the disease. According to the model, 140,312 (17.42%) symptom-reporting participants likely were infected, representing 5.36% of the full study cohort.

HOW IT WAS DONE

The COVID Symptom Study app was released for free in the U.K. on March 24, and in the U.S. on March 29 to residents with or without apparent COVID-19 symptoms. Users record their location, age and core health-risk factors upon initial use, and then update the tool daily with their symptoms, healthcare encounters, diagnostic test results and quarantine behaviors.

Relationships between symptoms and COVID-19 test results were identified via multivariate logistic regression with adjustments for age, sex and BMI.

The researchers highlighted a handful of limitations inherent to their study design, chief among which were the reliance on self-reported data, rather than physiologic assessment, and participant self-enrollment. Further, because SARS-CoV-2 testing is more common among those with likely cases, the model's training sample was not representative of the general population.

THE LARGER TREND

The last couple of months have seen a wave of digital symptom-checkers, like the COVID Symptom Study app, released by technology companies, health systems and governments alike. In fact, just this weekend the World Health Organization shared plans for a symptom-checker app that it will be providing to countries without the resources to build and distribute their own digital tool.

The debate over whether these apps and others for contact tracing are appropriate (or even effective) is ongoing. Albeat its sampling caveats, the Nature study offers an example of how large-scale data collection could be used to help public health identify predictors of the disease and understand its potential spread.

Austin, Texas-based EverlyWell, a digital platform that lets consumers order lab tests online and view their results, has received an FDA Emergency Use Authorization (EUA) for a COVID-19 at-home diagnostic sample collection kit that can be used with multiple diagnostic lab tests.

Announced Friday by the FDA and Monday by the startup, the EverlyWell COVID-19 Test Home Collection Kit includes nasal swabs, a tube filled with saline and shipping instructions.

These samples are sent to a CLIA-certified lab equipped to run one of two in vitro diagnostic molecular tests that have been granted separate EUAs for use with EverlyWell's kit.

Results are returned to the patient through EverlyWell's digital platform within 48 hours of lab receipt and, if positive, will include a telehealth consult and appropriate case reporting.

"Widespread access to convenient testing will play a crucial role in the country's ability to address the pandemic and prevent overburdening our healthcare facilities," Julia Cheek, CEO and founder of EverlyWell, said in a statement. "As the national leader in connecting people with high-quality laboratory testing, we are committed to fighting the spread of this virus in America."

To receive the kit, consumers must complete a digital screening questionnaire that is reviewed by an EverlyWell provider. The kits and service will run customers $109, a figure that EverlyWell stressed in its announcement provides no profit to the company.

The announcement also notes that EverlyWell will provide the necessary information for customers to submit a reimbursement claim with their insurance, but that the test is not currently covered by certain policies.

"EverlyWell ... is working with Congress to find a legislative solution to limitations that prevent companies like EverlyWell, which provides access to testing, but is neither a medical provider [nor] a laboratory providing COVID-19 testing services, from being directly reimbursed by insurers," the company wrote in its announcement. "The company has also reached out to policymakers to explore funding possibilities for making the tests available for free."

WHY IT MATTERS

This authorization comes two months after EverlyWell announced the launch of an at-home sample-collection kit that it believed was permitted under an FDA policy that permits COVID-19 testing to certain labs prior to receipt of an EUA. EverlyWell and others rescinded these consumer offerings within a week after clarification from the agency that these guidances did not apply to at-home consumer products.

"We share the FDA’s concern regarding fraudulent tests and are working directly with the FDA to increase the availability of COVID-19 testing," the company said at the time.

It's clear that the testing startup continued to do just that, as the EUAs for EverlyWell's kit and the associated lab diagnostic tests were well publicized by the FDA. In particular, the agency highlighted the public health benefits of a flexible at-home sample collection kit.

“The authorization of a COVID-19 at-home collection kit that can be used with multiple tests at multiple labs not only provides increased patient access to tests, but also protects others from potential exposure,” Dr. Jeffrey Shuren, director of the FDA’s Center for Devices and Radiological Health, said in a statement. “[Friday]’s action is also another great example of public-private partnerships in which data from a privately funded study was used by industry to support an EUA request, saving precious time as we continue our fight against this pandemic.”

THE LARGER TREND

It appears the floodgates are finally beginning to open for at-home COVID-19 sample collection. LabCorp's COVID-19 RT-PCR test was the first to receive the agency's blessing in mid-April, but last week saw at least two other consumer-facing telehealth brands announce the availability of testing kits for another recently authorized saliva test for the disease.