Objectives: To determine the effect of concurrent infection with multiple high-risk types of human papillomavirus (HPV) infection on the risk of cervical cytological abnormalities among female sex workers from Kenya.

Methods: Type-specific HPV DNA was detected using PGMY09/11 PCR (Roche) on baseline samples from 296 female sex workers (FSW) from Nairobi, Kenya. Exfoliated cervical cells were collected for cytological screening by ThinPrep liquid-based cytology (Cytyc). Demographic and sexual history was obtained. Blood specimens were tested for HIV-1 seropositivity by ELISA.

Results: Overall, 82 (27.7%) women were concurrently infected with more than one high-risk HPV (HR HPV) type. There was an increase in prevalence of multiple HR HPV infection with increasing severity of cervical cytology (23.5% of ASCUS, 48.1% of LSIL, and 62.5% of HSIL/ASC-H). HIV-1 seropositive women had an increased risk of multiple HR HPV infection (OR: 4.9; 95%CI: 2.6-9.0) as compared to HIV-1 seronegative women. In multivariate analysis, adjusting for age, HIV status, and duration of sex work, multiple HR HPV infection increased the risk of LSIL (OR=2.6; 95%CI: 1.1-6.4) and HSIL/ASC-H (OR=5.7; 95%CI: 1.7-19.2). Multiple HR HPV infections were associated with a higher risk of LSIL (aOR=1.17; 95%CI 0.3-5.2) and HSIL (aOR=7.9; 95%CI 0.8-82.0) among HIV positive women, although associations were imprecise. HIV seronegative women with multiple HR HPV infection had a higher risk of LSIL (aOR=4.0; 95%CI: 1.3-12.0) and HSIL (aOR=4.3; 95%CI: 1.0-18.0) as compared to HIV-1 seronegative women without multiple HR HPV infections.

Conclusions: Concurrent infection with multiple HR HPV types is a risk marker for low grade and high grade cervical cytology. Given the current evidence that a specific individual HPV type is etiologically relevant for an individual cervical lesion, further investigation of concurrent infection with these high risk types in cervical histologically confirmed biopsies, stratified by HIV-serostatus, is justified.