Testing the Accuracy of a Digital Test to Diagnose Covid-19

ABSTRACT

ConditionCovid-19

InterventionDiagnostic Test Covid-19 swab PCR test

Primary outcome:SARS-CoV-2 infection;SARS-CoV-2 infection

Criteria
Study Inclusion Criteria - app users will be eligible to join the study if they

- Are based in the UK (are using the UK version of the Covid-19 Symptom Study app, and
have listed a UK postcode)

- Are the primary app user (are reporting directly for themselves)

- Are at least 18 years of age

- Have not tested positive for a Covid-19 test before (but may have been tested)

Study Exclusion Criteria - participants are ineligible for the study if they

- Do not meet inclusion criteria

- Do not provide informed consent to participate

Participants will be subject to further screening to identify them as eligible for swab
testing during the course of the study.

Swab inclusion criteria - participants will be eligible for swab testing if they

- Have reported in the app at least once in the previous 3 days (days -2 to 0), and at
least two times in the previous 9 days (days -8 to 0). All reports must be healthy
(i.e. not experiencing any symptoms).

- On the previous day (day 1), have reported that they are experiencing at least one
symptom described in the app. Symptoms in the app are updated when deemed appropriate
by study investigators using evidence based reports in the scientific and medical
field.

- Have answered the phenotype fields required for the prediction model with
physiologically plausible values.

Swab exclusion criteria - participants are ineligible for swab testing if they

- Are asymptomatic

- Do not satisfy the inclusion criteria for testing.

Insufficient testing capacity

If insufficient testing capacity is available for the study population as described, then
recruitment will be prioritised according to

- Firstly, most recent final healthy report before reporting symptoms

- Secondly, highest number of healthy reports during the previous 9 days before
reporting symptoms

- Thirdly, randomised selection to stratify between participants of equal priority
according to the first two rules above.

Excess testing capacity

If excess testing capacity is available beyond the study population as described, then
inclusion criteria will be expanded in order to adequately sample across under-represented
population groups.

Specifically, on day 7 of each validation phase, investigators will assess

- What excess testing capacity is available, if any

- Which subgroups are under-represented compared to their proportion in the UK
population (as best as can be established given that some participants may not have
completed some phenotype fields)

(i) Age decade (ii) Sex (iii) Ethnicity (iv) BMI category

For underrepresented groups, investigators may additionally recruit participants with only
one report during the previous 3 days (days -2 to 0) and no other report during the
previous 9 days (days -8 to 0).