SETTING: Sex Workers Outreach Programme Clinic, Korogocho, Nairobi, Kenya.

OBJECTIVE: In a cohort of sex workers, to determine 1) the prevalence of cervical intra-epithelial neoplasia (CIN) and its association with human immunodeficiency virus-1 (HIV-1) infection, and 2) the incidence rate of CIN during the 3-year follow-up from December 2009 to December 2012.

DESIGN: Prospective nested cohort study.

RESULTS: Of the 350 women enrolled, the median age was 29 years (range 18–49); 84 (24%) were HIV-1-infected. At enrollment, 54 (15%) had an abnormal cytology, 39 (11%) had low-grade intra-epithelial lesions (LSIL) and 15 (4%) high-grade intraepithelial lesions (HSIL). HIV-1-infected women were 2.7 times (95%CI 1.7–4.4) more likely to have CIN than non-HIV-1-infected women. Among HIV-1-infected women, the prevalence of LSIL and HSIL was 2.5 times (95%CI 1.2–5.1) and seven times (95%CI 2.3–23.3) greater than among non-HIV-infected women. During the follow-up period, 39 (11%) women had incident CIN (6.6/100 person years [py]), with no difference by HIV status, i.e., respectively 7.9/100 py and 6.3/100 py in HIV-1-infected and non-HIV-1-infected women.

CONCLUSION: The prevalence and incidence of CIN among HIV-1-infected sex workers was high; early, regular screening and follow-up of this life-threatening condition is therefore recommended.