title: The health informatics cohort enhancement project (HICE): using routinely collected primary care data to identify people with a lifetime diagnosis of psychotic disorder.
abstract: BACKGROUND
  We have previously demonstrated that routinely collected primary care data can be used to identify potential participants for trials in depression [1]. Here we demonstrate how patients with psychotic disorders can be identified from primary care records for potential inclusion in a cohort study. We discuss the strengths and limitations of this approach; assess its potential value and report challenges encountered.
  
  
  METHODS
  We designed an algorithm with which we searched for patients with a lifetime diagnosis of psychotic disorders within the Secure Anonymised Information Linkage (SAIL) database of routinely collected health data. The algorithm was validated against the "gold standard" of a well established operational criteria checklist for psychotic and affective illness (OPCRIT). Case notes of 100 patients from a community mental health team (CMHT) in Swansea were studied of whom 80 had matched GP records.
  
  
  RESULTS
  The algorithm had favourable test characteristics, with a very good ability to detect patients with psychotic disorders (sensitivity > 0.7) and an excellent ability not to falsely identify patients with psychotic disorders (specificity > 0.9).
  
  
  CONCLUSIONS
  With certain limitations our algorithm can be used to search the general practice data and reliably identify patients with psychotic disorders. This may be useful in identifying candidates for potential inclusion in cohort studies.
authors.affiliation: Centre for Health Information Research & Evaluation, ILS2, College of Medicine, Swansea University, Swansea, SA2 8PP, UK. k.r.lloyd@swansea.ac.uk.
authors.forename: Alexis
authors.initials: A
authors.lastname: Economou
authors.forename: Michelle
authors.initials: M
authors.lastname: Grey
authors.forename: Joanna
authors.initials: J
authors.lastname: McGregor
authors.forename: Nick
authors.initials: N
authors.lastname: Craddock
authors.forename: Ronan A
authors.initials: RA
authors.lastname: Lyons
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Owen
authors.forename: Vaughn
authors.initials: V
authors.lastname: Price
authors.forename: Sue
authors.initials: S
authors.lastname: Thomson
authors.forename: James Tr
authors.initials: JT
authors.lastname: Walters
authors.forename: Keith
authors.initials: K
authors.lastname: Lloyd