A cohort study comparing rate of repeat testing for sexually transmitted and blood-borne infections between clients of an internet-based testing programme and of sexually transmitted infection clinics in Vancouver, Canada

Objectives
Internet-based sexually transmitted and blood-borne infection (STBBI) testing services reduce testing barriers through bypassing face-to-face clinical encounters, potentially enabling clients at ongoing sexual risk to test more frequently. To our knowledge, this hypothesis has not been previously tested. We compared the frequency of repeat testing between Vancouver-based clients of GetCheckedOnline (GCO)—an internet-based STBBI testing service in British Columbia, Canada—and clients of three sexually transmitted infection (STI) clinics in Vancouver for 29 months after GCO launched.

Methods
An administrative data cohort (n=19 497) was assembled using GCO, clinical and laboratory databases. We included all individuals who tested for HIV, gonorrhoea/chlamydia, syphilis or hepatitis C at three STI clinics or using GCO, between September 2014 and February 2017. The rate of repeat testing (>30 days after first episode) was compared between clients who used GCO at least once and those who tested only in STI clinics. Poisson regression was used to generate relative rate (RR) for repeat testing, with adjustment for age, gender/sexual orientation, risk factors (eg, history of STI diagnosis) and rate of testing before GCO launched.

Results
1093 GCO clients were identified, of whom 434 (40%) had repeat test episodes; 8200/18 404 (45%) of clinic clients tested more than once. During the 29-month analysis period, GCO clients repeat tested 1.87 times per person-year, whereas clinic clients repeat tested 1.53 times per person-year, resulting in a crude RR of 1.22 (95% CI: 1.14 to 1.31). Adjustment for covariates increased the RR to 1.26 (95% CI: 1.15 to 1.37).

Conclusions
In this cohort, individuals using internet-based STBBI testing had a rate of repeat testing 22% greater than clinic-based clients. This effect was increased after adjusting for characteristics associated with higher test frequency. The online interface of GCO may facilitate more frequent testing and may therefore contribute to earlier STBBI diagnosis.