There is debate on the role of male circumcision in HIV transmission. Most
case-control and cohort studies from Africa have shown an association betwe
en a lack of circumcision and an increased risk of HIV infection in men. Th
e evidence is conflicting, however, with cross-sectional surveys from Tanza
nia and Rwanda either showing no relationship or an association in the oppo
site direction. A recent review and meta-analysis of the literature(1) conc
luded that the risk of HN infection was lower in uncircumcised men (combine
d odds ratio 0.94, 95% confidence interval 0.89 to 0.99). However, the anal
ysis was performed by simply pooling the data from 33 diverse studies, whic
h is an inappropriate method for combining studies.
We re-analysed the data, stratifying by study, and found that an intact for
eskin was associated with an increased risk of HIV infection: combined odds
ratio 1.43 (1.32 to 1.54) with a fixed effect model and 1.67 (1.25 to 2.24
) with a random effect model. There was significant between-study heterogen
eity (P < 0.0001) which was partly explained by stronger associations in st
udies in high-risk groups. The results from this re-analysis thus support t
he contention that male circumcision may offer protection against HIV infec
tion, particularly in high-risk groups where genital ulcers and other STDs
'drive' the HIV epidemic. A systematic review is required to clarify this i
ssue. Such a review should be based on an extensive search for relevant stu
dies, published and unpublished, and should include a careful assessment of
the design and methodological quality of studies. Much emphasis should be
given to the exploration of possible sources of heterogeneity. In view of t
he continued high prevalence and incidence of HIV in many countries in sub-
Saharan Africa, the question of whether circumcision could contribute to pr
event infections is of great importance, and a sound systematic review of t
he available evidence should be performed without delay.