Objective To evaluate the acceptability and effectiveness of a pilot intervention programme using gay geosocial mobile applications (apps) to offer rapid HIV and other STI tests to men who have sex with men (MSM) in Barcelona between December 2015 and March 2016.

Methodology We offered rapid HIV, syphilis and hepatitis C testing by sending private messages on apps for sexual and social encounters. Acceptance was defined as the proportion of users who favourably responded to the message and effectiveness was defined as the proportion of users who attended our facilities among those who were interested in attending. To identify variables associated with the response to the messages, multivariate logistic regression was used. Adjusted OR (OR_a) and 95% CIs were calculated. We collected information on sociodemographics, sexual behaviours and app usage from the contacted user profiles and from users who attended our facilities. A descriptive analysis was carried out.

Results 2656 individual messages were sent. Overall, a 38.4% response rate was obtained, 83.0% of them found it acceptable to receive the unsolicited message, and 73.2% effectiveness was obtained. Responders had higher odds of being 45 years or older (OR_a=1.48; 95% CI 1.06 to 2.08), being connected at the moment the message was sent or during the previous hour (OR_a=1.92; 95% CI 1.38 to 2.68), having a profile photo not exposing bare chest or abdomen (OR_a=1.44; 95% CI 1.07 to 1.92) and using the Grindr app (OR_a=1.39; 95% CI 1.12 to 1.73). Of those who were tested and took the survey (n=77), 45.5% had not taken an HIV test in over a year, 24.7% had had a previous STI diagnosis, 51.4% had reported anal sex without condom and 52% had consumed alcohol or drugs for sex.

Conclusions The response rate, acceptance and effectiveness observed in this study indicate that this strategy could be a useful tool for promoting STI testing among high-risk MSM population.