Relative risk of high grade squamous intraepithelial lesion associated with prior abnormal Pap smears.

OBJECTIVE Pap smear frequency remains controversial, especially for women with consecutive negative smears. We undertook the current study to ascertain the association of high grade squamous intraepithelial lesions (HSIL) and prior abnormal Paps. STUDY DESIGN Women with biopsy-proven HSIL (cervical intraepithelial neoplasia 2 and 3) diagnosed between September 1996 and December 1997 and age-matched controls with a negative Pap obtained during the same time period were selected. RESULTS Sixty-three cases (mean age = 32 years) of HSIL and 69 controls (mean age = 33 years) constituted the study population. Any prior abnormal diagnosis conferred a 15-fold increased risk of HSIL on the current Pap (50/63 vs. 14/69, P < .0001). When limited to the 60 women with at least three prior Paps, the odds ratio for HSIL on the current Pap with any prior abnormal was 18 (28/31 vs. 10/29, P < .0001). Three cases had at least three consecutive negative Paps prior to the diagnosis of HSIL. CONCLUSION Women with one or more prior negative Pap smears had a significantly decreased risk of HSIL on the current Pap. Consecutive negative Paps did not appear to further decrease the risk; 10% of HSIL patients had had three or more consecutive prior negative Paps. To detect HSIL at its earliest stage, women should be advised to continue annual Pap screening in spite of consecutive negative results.