The oncogenic potential of human papillomavirus (HPV) infection was assessed by following the disease course in 455 patients who had had a routine diagnostic Hybrid Capture HPV test due to squamous cell abnormalities of the uterine cervix as detected by cytology and/or colposcopy. At entry, 308 patients had cytologic atypia classified as P3 by the Papanicolau classification, 168 had a positive high-risk HPV test, and 23 were infected only with low-risk HPV. The patients were followed-up using the patient registry until the endpoint of histologically diagnosed cervical intraepithelial neoplasia (CIN). High-grade CIN was diagnosed in 75 surgical biopsies. High-risk HPV infection (relative risk: 76.8 CI 95 : 23.7-249.5), cytologic atypia (RR: 16.2 CI 95 : 3.9-66.6), and age above 35 (RR: 1.99 CI 95 : 1.26-3.16) were independent risk factors for high-grade CIN, while the viral load did not predict oncogenic progression (P ¼ 0.47). After PCR-RFLP typing, the high-risk types were classified into groups as follows:
(1) types 16 and 18, (2) types 45, 52, and 56, (3) types 31, 33, 35, 51, and 58. The relative risks of high-grade CIN were 119.1 (CI 95 : 36.2-390.9) for group 1, 44.4 (CI 95 : 9.8-201) for group 2, and 39.7 (CI 95 : 10.9-144.8) for group 3, respectively. The risk ratios between the groups of high-risk types were found to differ at most by a factor of 2.98 (corrected P value: 0.007) indicating that the oncogenic potential varies moderately within the high-risk group of HPVs.