Risk of cervical abnormality after age 50 in women with previously negative smears.

There is discussion over the benefit of continuing cervical screening in women over the age of 50 with a history of negative cytology. We aimed to determine the risk of abnormal cytology in such women. Screening history data from 1985 to 2003 were obtained for a cohort of 2 million women from the NHS cervical screening programme from four Health Authorities in England. The 57,651 women in the cohort who reached age 40 between 1 January 1985 and 31 December 1990 and had at least one routine or opportunistic smear between ages 50 and 54 were included in the analysis. Exposure groups (negative cytology history, negative but including inadequate smears, and positive history) were defined on the basis of screening histories from ages 40 to 49. Sixty-four percent (134/206) (95% CI: 57-71%) of the moderate dyskaryosis or worse lesions at ages over 50 were detected from women in the negative smear history group. After allowance for time since last negative smear, the relative risk for the first primary smear over the age of 50 having moderate dyskaryosis or worse decreased from 0.60 (95% CI: 0.41-0.84) for two negative smear episodes to 0.25 (95% CI: 0.10-0.56) for four negative smear episodes, compared with the positive history group. If screening were discontinued for all women over 50 with a negative history, the majority of cytological abnormalities now being detected at these ages that lead directly to referral to colposcopy would be missed.

The use of screening episodes linked to CIN3 and invasive cancer registrations to study outcomes from the NHS Cervical Screening Programme.

UNLABELLED: The use of screening episodes linked to CIN3 and invasive cancer registrations to study outcomes from the NHS Cervical Screening ProgrammeObjective: To examine how NHS cervical screening data can be collected and analysed in order to evaluate women's screening histories as episodes rather than as individual smears. DESIGN: Analysis of routine cervical screening data grouped into screening episodes for a cohort of women regarding episodes starting in a given year. SETTING: NHS Cervical Screening Programme. POPULATION: Data from four Health Authorities (now eight Primary Care Trusts) from the NHS Cervical Screening Programme with primary smears (first in an episode) taken between 1 April 1999 and 31 March 2000. METHODS: Cytology information obtained from the call/recall ('Exeter') computer system was linked to cervical intraepithelial neoplasia (CIN) 3 and invasive cancer outcome information obtained from cancer registries. Screening histories were divided into episodes, each starting with a primary smear that was followed up to episode closure or, for episodes still open followed for an average 4.25 years, from the primary smear. The episode was divided into two parts (up to referral to colposcopy and following the referral). The outcomes of the episodes are described including referral rate to colposcopy and CIN3 and invasive cancer rates by factors such as age. MAIN OUTCOME MEASURES: Episode histories and rates of referral to colposcopy, CIN3 and invasive cancer. RESULTS: There were 176 923 episodes from 176 319 women (1.003 episodes per woman) followed up to March 2004, the date at which the first phase of information accrual ceased. Of these episodes, 172 100 (97.3%) were closed either by a negative smear referring the woman back to routine recall or by default (defined as no smear recorded within 21 months following a smear requiring an action of repeat or refer to colposcopy). The remaining 4823 (2.7%) of episodes were still open, of which in 3121 (1.8%) the woman had been referred to colposcopy and in 1702 (1.0%) no referral decision had been made. Referral rates to colposcopy varied by age from 5.7% in women aged 20-24 years down to 0.9% in women aged 60-64 years. The overall efficiency of screening was highest for woman aged about 30 years, with a CIN3 detection rate of eight per 1000 women and a positive predictive value (for CIN3 or worse) of referral to colposcopy of 21%. CONCLUSION: The study has shown that routinely collected NHS cervical screening data can be combined to give information on complete episodes, allowing important performance measures to be studied. We suggest that in future information in the NHS screening system should be structured to facilitate such analysis and to allow cytology and histology information to be readily linked.