Originally posted on January 14. 2012
For several years, many organizations have argued that the best way to reduce HIV infections in Africa is to circumcise men and boys. These groups cite three randomized clinical trials (RCTs) as conclusive proof that circumcision prevents HIV. Since then, several governments have pushed for male circumcision. However, a recent paper challenges that effort.
Robert S. Van Howe and Michelle R. Storms dissected the results of the RCTs. They argue that the trials all shared the same “expectation bias (both researcher and participant), selection bias, lead-time bias, attrition bias, duration bias, and early termination that favored the treatment effect the investigators were hoping for.” These biases resulted in the assumption that all HIV infections come from heterosexual sex, and so none of the researchers bothered to actually check where the infections came from. The researchers may have potentially overstated the number of HIV infections from heterosexual sex:
In the South African trial, men who reported at least one episode of unprotected sex accounted for 2498 person-years and 46 HIV infections during the trial. Among the remaining men, who accounted for 2076 person-years, 23 become infected although they either had no sexual contact or always used a condom. These men, who had infection rate of 1.11/100 person-years (95%CI=0.74-1.67), presumably became infected through non-sexual means. The men at sexual risk of infection had an infection rate of 1.84/100 person-years (95%CI=1.38-2.46). It would be expected that all men in the trial shared the same baseline risk of non-sexual transmission and any additional risk could be attributed to sexual transmission. The infections attributed to sexual contact would be the difference between the total rate and the non-sexually transmitted rate (0.73/100 person-years). Consequently, only 18 (0.0073 infections per person-year * 2498 person-years) of the 69 infections in the South African trial can be attributed to sexual transmission.