Background: Crowdsourcing is used increasingly in health and medical research. Crowdsourcing is the process of aggregating crowd wisdom to solve a problem. The purpose of this systematic review is to summarize quantitative evidence on crowdsourcing to improve health. Methods: We followed Cochrane systematic review guidance and systematically searched seven databases up to September 4th 2019. Studies were included if they reported on crowdsourcing and related to health or medicine. Studies were excluded if recruitment was the only use of crowdsourcing. We determined the level of evidence associated with review findings using the GRADE approach. Results: We screened 3508 citations, accessed 362 articles, and included 188 studies. Ninety-six studies examined effectiveness, 127 examined feasibility, and 37 examined cost. The most common purposes were to evaluate surgical skills (17 studies), to create sexual health messages (seven studies), and to provide layperson cardiopulmonary resuscitation (CPR) out-of-hospital (six studies). Seventeen observational studies used crowdsourcing to evaluate surgical skills, finding that crowdsourcing evaluation was as effective as expert evaluation (low quality). Four studies used a challenge contest to solicit human immunodeficiency virus (HIV) testing promotion materials and increase HIV testing rates (moderate quality), and two of the four studies found this approach saved money. Three studies suggested that an interactive technology system increased rates of layperson initiated CPR out-ofhospital (moderate quality). However, studies analyzing crowdsourcing to evaluate surgical skills and laypersoninitiated CPR were only from high-income countries. Five studies examined crowdsourcing to inform artificial intelligence projects, most often related to annotation of medical data. Crowdsourcing was evaluated using different outcomes, limiting the extent to which studies could be pooled. Conclusions: Crowdsourcing has been used to improve health in many settings. Although crowdsourcing is effective at improving behavioral outcomes, more research is needed to understand effects on clinical outcomes and costs. More research is needed on crowdsourcing as a tool to develop artificial intelligence systems in medicine.

The effectiveness of HIV pre-exposure prophylaxis (PrEP) depends on adherence, which requires retention in PrEP care. We sought to examine factors associated with six-month retention in PrEP care among individuals prescribed PrEP between 2011 and 2015 in a large, academic health system in the Bronx, New York. We used multivariable logistic regression to identify factors independently associated with six-month retention. Among 107 patients, retention at six months was 42%. In the multivariable analysis, heterosexual individuals were less likely to be retained in PrEP care at six months, but individuals who received prescriptions from attending physicians were more likely to be retained in care. Larger prospective studies are needed to better evaluate the individual and health system factors associated with long-term engagement in PrEP care.

Author Contributions: Drs Fishman and Gross contributed equally to this study. Drs Bien-Gund and Fishman had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Background: People with HIV (PWH) smoke tobacco at much higher rates than the general population. Previous research has shown that PWH have faster nicotine metabolism than HIVuninfected individuals, which may underlie this disparity, but the cause is unknown. We investigated whether higher nicotine metabolite ratio (NMR; 3-hydroxycotinine:cotinine), a validated biomarker of nicotine metabolism through CYP2A6, was associated with antiretroviral use among HIV-infected smokers. Methods:We conducted a retrospective cohort study of HIVpositive smokers in the University of Pennsylvania Center for AIDS Research cohort. We compared the NMR before viral suppression (.10,000 copies/mL) and after viral suppression on antiretroviral therapy (,200 copies/mL). We used mixed-effects linear regression to analyze the change in NMR after viral suppression and assessed for effect modification by efavirenz use.Results: Eighty-nine individuals were included in the study. We observed effect modification by efavirenz use (interaction term for efavirenz use, P , 0.001). Among those on nonefavirenz regimens, the mean NMR increased by 0.14 (95% confidence interval: 0.05 to 0.23, P = 0.002). Among those on efavirenz-containing regimens, the mean NMR increased by 0.53 (95% confidence interval: 0.39-0.66, P , 0.001). Conclusions:We observed a clinically and statistically significant increase in NMR after viral suppression among smokers with HIV, which more than doubled among those on efavirenz-based regimens. Higher NMR among HIV-positive smokers on antiretroviral therapy may help explain the higher rates of tobacco use and lower quit rates among PWH in care. These findings suggest that regimen choice and other modifiable factors may be targets for future attempts to increase success rates for tobacco cessation among PWH.