Background Recruitment plays a vital role in conducting randomized control trials (RCTs). Challenges and failure of proper recruitment lead to early termination of trials. Monetary incentives have been suggested as a potential solution to these challenges. Therefore, we aimed to do a systematic review and analysis to evaluate the effect of incentives on the number of participants willing to consent to and participate in RCTs. Methods Electronic databases were systematically searched from inception to September 23rd, 2021, using the following keywords: payments, incentive, response, participation, enrollment, randomized, randomization, and RCT. The Cochrane Risk of Bias tool was used to assess the quality of the included trials. Risk ratios (RRs) were calculated with their corresponding 95% confidence interval (CI). All analyses were done with the random-effects model. We used Revman software to perform the analysis. Results Six RCTs with 6,253 Participants met the inclusion criteria. Our analysis showed significant improvement in response rate (RR: 1.27; 95% CI: 1.04, 1.55; P = 0.02) and consent rates (RR: 1.44; 95% CI: 1.11, 1.85; P = 0.006) when an incentive payment was offered to participants. Even a small amount of incentive showed significant improvement in both consent (RR: 1.33; 95% CI: 1.03, 1.73; P = 0.03) and response rates (RR: 1.26; 95% CI: 1.08, 1.47; P = 0.004). Conclusion In conclusion, our meta-analysis demonstrated statistically significant increases in the rate of consent and responses from participants when offered even small monetary value incentives. These findings suggest that incentives may be used to reduce the rate of recruitment failure and subsequent study termination. However, further RCTs are needed to establish a critical threshold beyond which incentive amount does not alter response rates further and the types of RCTs in which financial incentives are likely to be effective.

Background The current literature shows increasing concerns about potential seminal transmission of monkeypox virus (MPV). Accordingly, we aimed to understand better the potential presence of MPV in the seminal uids and others specimens obtained from monkeypox (MPX) cases.Methods On June 26, 2022, a systematic search of the literature was conducted across PubMed, Scopus, Web of Science, EMBASE, ScienceDirect, ProQuest, EBSCOHost-Academic Search Complete, and Google Scholar to nd articles that examine the presence of MPV in seminal uid of con rmed cases . The search was updated on August 12 to include newly published articles. The prevalence of MPV DNA presence in the seminal uid and other specimens was pooled in a meta-analysis and results were presented as effect sizes and their corresponding 95% con dence intervals (CI). The quality of included articles was assessed using the National Institute of Health tool.Results Eight articles (including 585 MPX-con rmed patients) were included. Only four studies were eligible for a meta-analysis, and the individual positivity rate of MPV DNA in semen specimens ranged from 61.11% to as high as 90.62%, while the pooled rate was 78% (95% CI: 62-93%; I2=61.93%) among 91 examined patients. Moreover, the pooled positive rate of MPV DNA was the highest in rectal samples (100%; 95%CI: 94-100%), followed by urinary (31%; 95%CI: 1-61%), nasopharyngeal (28%; 95%CI: 24-32%), and blood/plasma (8%; 95%CI: 6-10%) samples, respectively. Furthermore, two articles also investigated the infectivity of MPV particles detected in seminal specimens by testing their replication competence. Culturing MPV was successful in one out of three patients included in these studies. Also, based on available evidence, the positivity of MPV in semen specimens can be observed early and up to 19 days after symptoms onset.Conclusions MPV is highly prevalent in seminal specimens of MPX cases, further corroborating the role of sexual transmission of the disease. However, further evidence is still needed to shed more light on the replication competence of these particles.