Molecular diagnosis of genital HPV DNA types by polymerase chain reaction and sensitivity-standardized filter in situ hybridization in randomly sampled cohorts of Singapore women.

Infection of the cervix uteri with various types of human papillomaviruses is generally considered a necessary factor in the etiology of cancer of the cervix uteri. In many human populations throughout the world, approximately 90% of cervical carcinomas are found to harbour HPV genomes, as judged by Southern blot hybridization, while only a few percent of the cervical smears of asymptomatic individuals contain viral DNA, as assessed by filter in situ hybridization. To obtain corresponding epidemiological data from Singapore, we analysed two groups of 740 and 130 individuals by filter in situ hybridization, and found 4.1% and 6.9% of them to be HPV positive, with HPV 16 and HPV 31 being the predominant types. In consideration of the limitations of filter in situ hybridization, namely low sensitivity and a tendency to suggest false positives due to contaminants, including blood, we analysed the cervical smears of two further groups of 52 and 50 individuals by the polymerase chain reaction for infection by HPV 16 and HPV 18 respectively. With this test, 61% and 14% of the cervical smears proved to be HPV 16 and HPV 18 DNA positive respectively. We conclude that in Singapore, if not worldwide, the majority of the population the population is infected by genital HPV types, suggesting that factors other than HPV infection are ultimately rate-limiting in cervical carcinogenesis.