Cervical cancer after multiple negative cytologic tests in long-term members of a prepaid health plan.

To estimate squamous cell cervical cancer incidence within 3.5 years of 1, 2 and > or = 3 consecutive, normal cytologic tests.Data were from a case-control study of cervical cancer screening efficacy. Long-term members of a prepaid health plan diagnosed with cancer from 1983 to 1995 (the cases) were grouped by number of prior conventional cytologic tests and by time from the last negative screening test to the diagnosis date. Women from the population at risk were estimated by multiplying the timated by multiplying the proportions of women without cancer (the matched controls) in each screening category by the numbers of long-term of the numbers of long-term female members enrolled from male members enrolled from 1983 to 1995.Of an estimated 6,802,641 woman-years of observation, 129 cases were diagnosed within 3.5 years of > or = 21 negative screening test. After > or = 3 consecutive negative tests, incidence per 100,000 woman-years grouped by time from the last negative screening test were: 1.43 (26/1,813,552) 0-18 months later, 4.24 (17/400,584) 19-30 months later and 4.73 (10/211,217) 31- 42 months later.The first 18 months after the last negative screening Pap test in women with > or = 3 prior negative tests, cancer incidence increases to an estimated 4-5 per 100,000 woman-years in each of the subsequent 2 years.