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

@entity5 @entity1 @entity3146
The use of screening episodes linked to CIN3 and invasive @entity5 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 @entity1 '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 @entity1 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 @entity3146 ( @entity3146 ) 3 and invasive @entity5 outcome information obtained from @entity5 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 @entity5 rates by factors such as age. MAIN OUTCOME MEASURES: Episode histories and rates of referral to colposcopy, CIN3 and invasive @entity5 . RESULTS: There were 176 923 episodes from 176 319 @entity1 (1.003 episodes per @entity1 ) 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 @entity1 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 @entity1 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 @entity1 aged 20-24 years down to 0.9% in @entity1 aged 60-64 years. The overall efficiency of screening was highest for @entity1 aged about 30 years, with a CIN3 detection rate of eight per 1000 @entity1 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.
