Screening for high- and low-risk human papillomavirus types in single routine cervical smears by non-isotopic in situ hybridization

Routine cervical smears (n = 262) from a Sexually Transmitted Diseases clinic were screened by non-isotopic in situ hybridization (NISH) stratifying human papillomavirus (HPV) infections into HPV6/11 (low risk) and HPV16/18/33 (high risk) categories. Of 188 patients with cytologically normal smears, HPV sequences were demonstrated in 41 %. Of the 128 cases analysed by dual NISH, 16 % contained low risk, 20 % high risk and 5 % both groups. In patients with cytological evidence of wart virus infection (WVI) only, 54 % (n = 50) contained high-risk and 22 % low-risk HPV types. The comparable incidences in CIN1/2 plus WVI (n = 24) were not significantly different: 54 % and 17 %, respectively. Cytological criteria underestimate the prevalance of HPV infection in patients with cytologically normal smears. This represents either 'occult' or 'latent' infection. The identical prevalence of HPVB16/18/33 in WVI only, and CIN1/2 plus WVI, suggests that the cytopathic effect induced by these HPVs may represent one end of a spectrum of morphological change which progresses to cervical intraepithelial neoplasia (CIN).