The age-specific prevalence of human papillomavirus and risk of cytologic abnormalities in rural Nigeria: implications for screen-and-treat strategies.

Cervical screening for carcinogenic human papillomavirus (HPV) infection is being considered for low-income countries. Effectiveness requires targeted screening in older women in whom prevalent infections are more likely to be persistent and predictive of precancer. Some studies in West Africa have found unusually high HPV prevalences across all adult ages, which may reduce the positive predictive value (PPV) of HPV-based screening, if positivity in older women does not sufficiently predict elevated risk. We conducted a population-based study in rural Nigeria to identify HPV prevalence and associated cervical abnormalities. Using stratified random sampling, we enrolled women age 15+. Nonvirgins had a cervical exam including liquid-based cytology and PCR HPV DNA testing from residual cytology specimens. Two-thirds of invited women participated, and 14.7% had detectable carcinogenic HPV, a proportion that did not decline with age (p-trend = 0.36) and showed slight peaks in the 15-29 and 60-69 age groups. Among women of the age typically considered for screen-and-treat programs (30-49 years), 12.8% were HPV positive, and the PPV for high-grade or worse cytology was 16.4%. Comparatively, women age < 30 were more likely to be HPV positive (18.9%, p = 0.03) with a lower PPV (4.2% p = 0.05). Among women age 50+ (typically excluded from screening in resource-poor settings because inexpensive treatment is not available), HPV positivity was 14.2% with a PPV of 13.9%. In Irun and similar settings where HPV does not decline with age, HPV-based screen-and-treat programs might be feasible for mid-adult women because prevalence is sufficiently low and positivity predicts elevated risk of more easily treated precancer.