Reproducibility of the cytologic diagnosis of human papillomavirus infection.

As part of a larger epidemiologic investigation of the association between human papillomavirus (HPV) infection and cervical intraepithelial neoplasia, the reliability of the cytologic diagnosis of HPV infection was examined. A random sample of cervicovaginal specimens with cytologic changes characteristic of HPV infection were matched with a second set of slides, with regard to the date and severity of the smear and the age of the woman from whom the smear was obtained. The kappa statistic for interobserver agreement was 0.38 (p less than 0.0005), increasing to 0.68 (p less than 0.0005) when uncertain diagnoses were excluded. Intraobserver agreement ranged from kappa = 0.40 to 1.00. Although this agreement is within the range of reliability found for the diagnosis of other atypical cytologic changes, considerable variation is present. The effect of this variability on the validity of estimating the risk of cervical cancer associated with HPV infection may be considerable.