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Background New innovative technologies, such as mobile apps, have been developed to increase pre-exposure prophylaxis (PrEP) adherence and the use of log sex diaries. The contiguity of mobile apps reduces the recall bias that generally affects reported condom and PrEP use. However, none of the currently used mobile apps were designed for event-driven PrEP users, and few studies have demonstrated the potential usage of sex diary data to facilitate the understanding of the different HIV risks among heterogeneous profiles of sex diaries and PrEP use. Objective We aim to discriminate the heterogeneous profiles of sex events and PrEP use and examine the risk of condomless anal sex among different types of sex events. Methods We recruited 35 adult men who have sex with men from two medical centers in Taiwan since May 2020 and followed up for four months. Participants were on PrEP or willing to take PrEP. They were asked to log their sex events, PrEP use, and dosing regimens on a mobile app to improve their PrEP adherence. Latent class analysis was used to distinguish profiles of sex events and PrEP use. Indicators included correct intake of PrEP for each sex event, participants’ sexual positioning, partner’s HIV status, and age. Results A total of 551 sex events were classified into three classes by latent class analysis: PrEP nonadherent flip-flopping (234/551, 42%), PrEP imperfect-adherent power bottoming (284/551, 52%), and PrEP adherent serodiscordant topping (33/551, 6%). “PrEP nonadherent flip-flopping” sex events were more likely to involve condomless anal sex than “PrEP imperfect-adherent power bottoming” (OR 1.83, 95% CI 1.03-3.25) after considering random intercepts for individuals, and this class needed to increase their PrEP adherence and use of condoms. “PrEP imperfect-adherent power bottoming” realized their own risk and packaged PrEP with condoms to protect themselves. Up to 99% (32/33) of sex events in “PrEP adherent serodiscordant topping” were protected by PrEP, but all of the sex events in this group were condomless. Conclusions Using the sex diary data could advance the capacity to identify high-risk groups. HIV prevention strategy should be more flexible and combine PrEP with condom use for future HIV prevention.

Objective The UPrEPU mobile app is a self-monitoring system to enable men who have sex with men to optimize their pre-exposure prophylaxis adherence for HIV prevention. The app was designed to accommodate a rather complicated event-driven dosing schedule. We aim to evaluate the usability of the UPrEPU app and its effectiveness in improving adherence monitoring. Methods From May to October 2020, 35 participants were enrolled for the usability study and followed up for 4 months. Blood samples for the drug concentration in the dried blood spots were obtained once during the second to fourth follow-up visits. The effectiveness of adherence monitoring was analyzed using Cohen's kappa statistic to calculate the concordance between the average number of pills taken and drug concentration in the dried blood spots. Results Overall retention was 91.4% (32 participants) at the end of the study. Participants used the app for a mean of 29 days and made 2565 data entries in total, with an average of 76 data entries. The average systematic usability scale score for the app was 71.5, indicating acceptable usability. Slight agreement was reached between the dried blood spots measurement and the number of pills taken and recorded in the app (weighted kappa: 0.21). Conclusions Our user-centered UPrEPU app demonstrated that it could accommodate both daily and event-driven dosing schedules for men who have sex with men clients with acceptable usability scores. We confirmed that complex behaviors such as different drug-dosing regimens that are contingent on sexual behaviors could be incorporated into the design of a mobile app.

This study aimed to examine whether adolescents select friends based on their friends’ levels of depressive symptoms, and to determine whether the potential homophily phenomenon for depressive symptoms is attenuated after considering pubertal maturation and gender. Data were from the first three waves of the Taiwan Youth Project, a longitudinal study that annually surveys 7th graders from 40 junior high schools. Participants were asked at each wave to fill out a survey including depressive symptoms, pubertal maturation, and to name three best friends in school. Stochastic actor-oriented models were built to explore the dynamic changes in friendship networks by estimating the probability of the friendship connections and behavioral changes depending on the individual’s current network position and behavioral status. We used a sample of 2,336 adolescents. From 8 to 9th grade, adolescents tended to select friends who were similar in terms of their levels of depressive symptoms (B = 0.358, SE = 0.131, p < .001), without adjusting for gender and pubertal maturation. This homophily effect based on depressive symptoms became non-significant when pubertal maturation was included. Adolescents’ depressive symptoms did not further influence their friends’ depression levels, after controlling for pubertal maturation and gender. Future studies should further examine the mechanisms and group dynamics within clusters of adolescents who are depressed. Providing a supportive environment and tools is warranted to help adolescents cope with negative emotions within their peer group.

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