title: Validation of the Hospital Episode Statistics Outpatient Dataset in England.
abstract: OBJECTIVE
  The Hospital Episode Statistics (HES) dataset is a source of administrative 'big data' with potential for costing purposes in economic evaluations alongside clinical trials. This study assesses the validity of coverage in the HES outpatient dataset.
  
  
  METHODS
  Men who died of, or with, prostate cancer were selected from a prostate-cancer screening trial (CAP, Cluster randomised triAl of PSA testing for Prostate cancer). Details of visits that took place after 1/4/2003 to hospital outpatient departments for conditions related to prostate cancer were extracted from medical records (MR); these appointments were sought in the HES outpatient dataset based on date. The matching procedure was repeated for periods before and after 1/4/2008, when the HES outpatient dataset was accredited as a national statistic.
  
  
  RESULTS
  4922 outpatient appointments were extracted from MR for 370 men. 4088 appointments recorded in MR were identified in the HES outpatient dataset (83.1%; 95% confidence interval [CI] 82.0-84.1). For appointments occurring prior to 1/4/2008, 2195/2755 (79.7%; 95% CI 78.2-81.2) matches were observed, while 1893/2167 (87.4%; 95% CI 86.0-88.9) appointments occurring after 1/4/2008 were identified (p for difference <0.001). 215/370 men (58.1%) had at least one appointment in the MR review that was unmatched in HES, 155 men (41.9%) had all their appointments identified, and 20 men (5.4%) had no appointments identified in HES.
  
  
  CONCLUSIONS
  The HES outpatient dataset appears reasonably valid for research, particularly following accreditation. The dataset may be a suitable alternative to collecting MR data from hospital notes within a trial, although caution should be exercised with data collected prior to accreditation.
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK. joanna.thorn@bristol.ac.uk.
authors.forename: Joanna C
authors.initials: JC
authors.lastname: Thorn
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: Emma
authors.initials: E
authors.lastname: Turner
authors.affiliation: Public Health England Knowledge and Intelligence Team (South West), 2 Rivergate, Temple Quay, Bristol, BS1 6EH, UK.
authors.forename: Luke
authors.initials: L
authors.lastname: Hounsome
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: Eleanor
authors.initials: E
authors.lastname: Walsh
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: Jenny L
authors.initials: JL
authors.lastname: Donovan
authors.affiliation: Public Health England Knowledge and Intelligence Team (South West), 2 Rivergate, Temple Quay, Bristol, BS1 6EH, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Verne
authors.affiliation: Department of Oncology, Addenbrooke's Hospital, University of Cambridge, Box 279 (S4), Hills Road, Cambridge, CB2 0QQ, UK.
authors.forename: David E
authors.initials: DE
authors.lastname: Neal
authors.affiliation: Nuffield Department of Surgical Sciences, University of Oxford, Old Road Campus Research Building, Oxford, OX3 7DQ, UK.
authors.forename: Freddie C
authors.initials: FC
authors.lastname: Hamdy
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Martin
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK.
authors.forename: Sian M
authors.initials: SM
authors.lastname: Noble
mesh_terms: D000368:Aged; D001071:Appointments and Schedules; D016208:Databases, Factual / Q000706:statistics & numerical data*; D004470:Economics, Medical; D004739:England; D006761:Hospitals / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D010045:Outpatients / Q000706:statistics & numerical data; D011471:Prostatic Neoplasms / Q000191:economics* / Q000628:therapy; D016032:Randomized Controlled Trials as Topic; D012107:Research Design