Time trends in the prevalence of human papillomavirus infections in archival Papanicolaou smears: Analysis by cytology, DNA hybridization, and polymerase chain reaction

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Abstract
A retrospective study was undertaken to determine the prevalence of human papillomavirus (HPV) infections in routine Papanicolaou (Pap) smears collected by general practitioners from Western Australian women in each of the years 1972, 1982, and 1987. HPV infection was detected by cytology, dot‐blot hybridization, or polymerase chain reaction (PCR). It was found that the prevalence of HPV infection remained unchanged over the 15 year study period, was independent of age, and was associated with normal cytology at a rate far greater than previously recognized. Indeed, the prevalence of cervical intraepithelial neoplasia (CIN) lesions, as detected by cytology, was 3.0% in 1972 and 3.8% in 1982 and 1987. The prevalence of HPV infection, detected as koilocytosis or parakeratosis, was 6.5%, 6.8%, and 5.3% in smears collected in 1972, 1982, and 1987, respectively, from 1,800 women. In 237 cytologically normal smears reprocessed for HPV‐DNA studies, the prevalence of HPV 16 was determined to be 15.6%, 11.2%, and 17.8% in 1972, 1982, and 1987, respectively, as determined by dot‐blot hybridization. However, the PCR detected HPV 16 in an additional 55.5%, 62.9%, and 57.0% of cytologically normal and dot‐blot negative smears. The prevalence of HPV 16 infection in cytologically normal smears was estimated to be 71.0%, 74.1%, and 74.8% in 1972, 1982, and 1987, respectively, by combining the HPV 16 dot‐blot and PCR‐positive results.The high prevalence of HPV 16 in cytologically normal Pap smears suggests that infection with HPV 16, as detected by PCR amplification, does not place women in a high‐risk category for cervical cancer. In addition, we have shown that the application of PCR on reprocessed Pap smears is a powerful and sensitive method for retrospectively evaluating any aetiological role of HPV infection in the development of cervical cancer.
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