Detection of human papillomavirus DNA in cytologically normal women and subsequent cervical squamous intraepithelial lesions.

Background: Human papillomavirus (HPV) infection has been strongly associated with cervical carcinoma and its cytologic precursors, squamous intraepithelial lesions (SIL). We investigated the risk of SIL prospectively following polymerase chain reaction (PCR)-based DNA testing for a wide range of genital HPV types in a cohort of initially cytologically normal women, to clarify the role of HPV in the etiology of SIL.
Methods: Starting in April 1989, 17,654 women who were receiving routine cytologic screening at Kaiser Permanente (Portland, OR) were followed for the development of incident SIL. During follow-up, 380 incident case patients and 1037 matched control subjects were eligible for this nested case-control study. Cervical lavages collected at enrollment and, later, at the time of case diagnosis (or the corresponding time for selection of control subjects) were tested for HPV DNA using a PCR-based method. The data were analyzed as contingency tables with two-sided P values or, for multivariable analyses, using odds ratios (ORs) with 95% confidence intervals (CIs).
Results: In comparison with initially HPV-negative women, women who tested positive for HPV DNA at enrollment were 3.8 times (95% CI = 2.6-5.5) more likely to have low-grade SIL subsequently diagnosed for the first time during follow-up and 12.7 times more likely (95% CI = 6.2-25.9) to develop high-grade SIL. At the time of diagnosis, the cross-sectional association of HPV DNA and SIL was extremely strong (OR = 44.4 and 95% CI = 24.2-81.5 for low-grade SIL and OR = 67.1 and 95% CI = 19.3-233.7 for high-grade SIL). HPV16 was the virus type most predictive of SIL, even low-grade SIL.
Conclusions: These findings are consistent with the hypothesis that HPV infection is the primary cause of cervical neoplasia. Furthermore, they support HPV vaccine research to prevent cervical cancer and efforts to develop HPV DNA diagnostic tests.