Human papillomavirus and cervical intraepithelial neoplasia grade II-III: a population-based case-control study.

The association between certain human papillomaviruses (HPV) and cervical intraepithelial neoplasia (CIN) is well documented, but there is uncertainty about the strength of association and the role of co-factors is unclear. This population-based case-control study in Norwegian women 20-44 years of age included 103 cases with histologically confirmed CIN II-III and 234 age-matched and randomly selected controls. Cytological specimens from the cervix were analyzed using the polymerase chain reaction (PCR). In all, 91% of the cases and 15% of the controls were HPV DNA positive, giving a crude odds ratio (OR) of 67.2 (95% confidence interval: 28.6-157.5). The association between HPV 16 and CIN II-III was even stronger (crude OR = 123.9; 46.7 - 328.5). In logistic regression analysis, additional to HPV, only a high number of sexual partners and a low educational level contributed independently to the risk. The adjusted OR for the association between HPV and CIN II-III was 72.8 (95% CI: 27.6-191.9). The association between HPV and CIN remains very strong even after adjustment for proposed confounding factors. The results therefore support the role of HPV as a causative agent in the development of CIN.