Cervical neoplasia in pap smears: risk of cervical intra-epithelial neoplasia (CIN) after negative or no prior smears in a population without a mass screening programme.
BACKGROUND: The aim of this study was to examine, in a population not submitted to mass screening, the risk of cancer and cervical intra-epithelial neoplasia (CIN) in Pap smears from women without previously reported positive smears. METHODS: In a logistic regression model consisting of 58,271 smears from 40,536 Norwegian women the risk of cytologically indicated CIN was studied according to age and time elapsed since last smear. RESULTS: The risk of CIN was highest in smears from women with no previously registered smears and in smears taken after an interval of > or = 5 years. Odds ratio for CIN I-II adjusted for age was highest in first time smears and in smears taken after an interval of 5 years. Odds ratio for CIN III was highest in first registered smears. No difference in risk of CIN III was found in smears taken within one year or 2-3 years after the last smear. The increased risk of CIN III in first smears was most pronounced in postmenopausal women ( > 50 years). Nine of 16 cases with cytological indication of cancer were found in women having a smear taken for the first time. All cases with malignancy in smears were > 50 years. CONCLUSIONS: The risk of cytologically diagnosed premalignant cervical conditions increases with time since the previous smear, but more than 5 years have to elapse before the risk is comparable with that in first smears taken. Postmenopausal women without previous smears run the highest risk of serious cervical premalignancies and cancer.