Thursday, 22 October 2009

Some HIV updates...

A recently published study, Templeton et al., reports:

On multivariate analysis controlling for behavioural risk factors, being circumcised was associated with a nonsignificant reduction in risk of HIV seroconversion [hazard ratio 0.78, 95% confidence interval (CI) 0.42-1.45, P = 0.424]. Among one-third of study participants who reported a preference for the insertive role in anal intercourse, being circumcised was associated with a significant reduction in HIV incidence after controlling for age and unprotected anal intercourse (UAI) (hazard ratio 0.11, 95% CI 0.03-0.80, P = 0.041).
This study provides valuable new data for evaluating the effect of circumcision among men who have sex with men (MSM). A meta-analysis published in 2008 by Millett et al. reported:
The odds of being HIV-positive were nonsignificantly lower among MSM who were circumcised than uncircumcised (odds ratio, 0.86; 95% confidence interval, 0.65-1.13; number of independent effect sizes [k] = 15).
But, of course, meta-analyses depends entirely on their source data; there is a need to update this earlier meta-analysis to include Templeton's findings. In particular, that earlier meta-analysis included only three studies in meta-analysis of the effect of circumcision among MSM favouring an insertive role in anal intercourse:
A separate analysis (not shown in Table 2) of 4 findings from 3 studies29, 33-34 reporting HIV infection and circumcision status for MSM who engaged exclusively or primarily in insertive anal intercourse (n = 2238) was protective, but not statistically significant (OR, 0.71; 95% CI, 0.23-2.22; k = 4). The power for this analysis was 0.94. Although there was high heterogeneity among these 4 findings (I2 = 90%), too few findings were available for a stratified analysis.
On a related topic, there are some reports from studies piggy-backing on the African RCTs that provide some new and interesting information about the mechanisms by which circumcision is protective against HIV. First, we have Johnson et al., who report:
Epithelial inflammation was present in 4.2% of men with neither HIV nor HSV-2 infection; 7.8% of men with only HSV-2; 19.0% with HIV alone (P = 0.04); and 31.6% in HIV/HSV-2 coinfected men [prevalence rate ratio (PRR) 7.5, 95% confidence interval (CI) 2.3-23.8, P < 0.001]. [...] Foreskin inflammation is increased with HIV and HSV-2 infections, higher HIV viral load and presence of smegma. Foreskin inflammation may have implications for HIV transmission and acquisition in uncircumcised men.
Next, we have Auvert et al., who report:
When controlling for all covariates, HIV incidence increased significantly with HR-HPV positivity (aIRR = 3.76, 95% CI: 1.83 to 7.73, P < 0.001) and with the number of HR-HPV genotypes (adjusted-P linear trend = 0.0074). [...] One [of several explanations] is that HR-HPV facilitates HIV acquisition.

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