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.

Determinants of genital human papillomavirus infection in low-risk women in Portland, Oregon.

OBJECTIVES: To confirm the risk factors for genital human papillomavirus (HPV) infection. GOAL OF THIS STUDY: To investigate risk factors for HPV detection independent of the correlated risk factors for cervical neoplasia in a low-risk population. STUDY DESIGN: HPV DNA was assessed among 483 cytologically normal women with no known history of cervical neoplasia. A cervicovaginal lavage was collected for HPV detection and typing using a PCR-based DNA amplification system. Information on risk factors of subjects was obtained through a questionnaire. RESULTS: HPV DNA was found in 17.7% of study women. On univariate analysis, factors associated with increasing HPV prevalence included younger age, fewer years of education, lower income, higher lifetime number of sex partners, lower age at first intercourse, nulliparity, oral contraceptive use, and current smoking. After statistical adjustment, we found younger age and higher number of sex partners were strongly and independently associated with higher HPV prevalence. We also observed increased HPV prevalence among women with lower levels of education and lower incomes. CONCLUSION: These findings and corroborative data from the companion reports in this issue of the journal support the sexual route of transmission of the virus.

Epidemiologic evidence showing that human papillomavirus infection causes most cervical intraepithelial neoplasia.

BACKGROUND: Experimental studies have provided strong evidence that human papillomavirus (HPV) is the long-sought venereal cause of cervical neoplasia, but the epidemiologic evidence has been inconsistent. PURPOSE: Given improvements in HPV testing that have revealed a strong link between sexual activity history and cervical HPV infection, we conducted a large case-control study of HPV and cervical intraepithelial neoplasia (CIN) to evaluate whether sexual behavior and the other established risk factors for CIN influence risk primarily via HPV infection. METHODS: We studied 500 women with CIN and 500 control subjects receiving cytologic screening at Kaiser Permanente, a large prepaid health plan, in Portland, Ore. The established epidemiologic risk factors for CIN were assessed by telephone interview. We performed HPV testing of cervicovaginal lavage specimens by gene amplification using polymerase chain reaction with a consensus primer to target the L1 gene region of HPV. Unconditional logistic regression analysis was used to estimate relative risk of CIN and to adjust the epidemiologic associations for HPV test results to demonstrate whether the associations were mediated by HPV. RESULTS: The case subjects demonstrated the typical epidemiologic profile of CIN: They had more sex partners, more cigarette smoking, earlier ages at first sexual intercourse, and lower socioeconomic status. Statistical adjustment for HPV infection substantially reduced the size of each of these case-control differences. Seventy-six percent of cases could be attributed to HPV infection; the results of cytologic review suggested that the true percentage was even higher. Once HPV infection was taken into account, an association of parity with risk of CIN was observed in both HPV-negative and HPV-positive women. CONCLUSION: The data show that the great majority of all grades of CIN can be attributed to HPV infection, particularly with the cancer-associated types of HPV. IMPLICATIONS: In light of this conclusion, the investigation of the natural history of HPV has preventive as well as etiologic importance.

Comparison of Southern blot hybridization and polymerase chain reaction methods for the detection of human papillomavirus DNA.

A methodologic study was performed to compare the polymerase chain reaction (PCR) and Southern blot hybridization, two commonly used testing strategies for the detection of human papillomavirus (HPV) infection. Three laboratories tested masked aliquots of exfoliated cervical cell specimens obtained from 120 women by cervicovaginal lavage. The study population included 32 women with condylomatous atypia or cervical intraepithelial neoplasia and 88 control women with no known history of cervical neoplasia. Two laboratories used PCR with different sets of consensus primers for HPV detection. The third laboratory used low-stringency Southern blot hybridization to identify all HPV types, followed by high-stringency Southern and/or dot blot hybridization to confirm specific HPV types. One of the PCR primer sets detected HPV types with a differential efficiency that was not predicted by analysis of DNA sequences or direct testing of HPV-containing plasmids. In contrast, the second PCR primer set was shown to be a much broader consensus system, detecting the same HPV types as Southern blotting, though requiring much less clinical specimen. Over 80% of women with cervical intraepithelial neoplasia or condylomatous atypia were found to be HPV infected both by Southern blotting and by the second PCR primer set. Among the control women, 11% were HPV positive by Southern blotting, while 31% were positive with the second set of primers. Most of the HPV infections found only by PCR were not due to HPV type 6, 11, 16, 18, 31, 33, or 45. These known HPV types were uncommon among normal women in the study population, even as determined by the PCR method.