title: Validation of administrative data used for the diagnosis of upper gastrointestinal events following nonsteroidal anti-inflammatory drug prescription.
abstract: OBJECTIVE
  To validate veterans affairs (VA) administrative data for the diagnosis of nonsteroidal anti-inflammatory drug (NSAID)-related upper gastrointestinal events (UGIE) and to develop a diagnostic algorithm.
  
  
  METHODS
  A retrospective study of veterans prescribed an NSAID as identified from the national pharmacy database merged with in-patient and out-patient data, followed by primary chart abstraction. Contingency tables were constructed to allow comparison with a random sample of patients prescribed an NSAID, but without UGIE. Multivariable logistic regression analysis was used to derive a predictive algorithm. Once derived, the algorithm was validated in a separate cohort of veterans.
  
  
  RESULTS
  Of 906 patients, 606 had a diagnostic code for UGIE; 300 were a random subsample of 11 744 patients (control). Only 161 had a confirmed UGIE. The positive predictive value (PPV) of diagnostic codes was poor, but improved from 27% to 51% with the addition of endoscopic procedural codes. The strongest predictors of UGIE were an in-patient ICD-9 code for gastric ulcer, duodenal ulcer and haemorrhage combined with upper endoscopy. This algorithm had a PPV of 73% when limited to patients >or=65 years (c-statistic 0.79). Validation of the algorithm revealed a PPV of 80% among patients with an overlapping NSAID prescription.
  
  
  CONCLUSIONS
  NSAID-related UGIE can be assessed using VA administrative data. The optimal algorithm includes an in-patient ICD-9 code for gastric or duodenal ulcer and gastrointestinal bleeding combined with a procedural code for upper endoscopy.
authors.affiliation: Houston Center for Quality of Care and Utilization Studies, Section of Health Services Research, Houston, TX, USA. nabraham@bcm.tmc.edu
authors.forename: N S
authors.initials: NS
authors.lastname: Abraham
authors.forename: D C
authors.initials: DC
authors.lastname: Cohen
authors.forename: B
authors.initials: B
authors.lastname: Rivers
authors.forename: P
authors.initials: P
authors.lastname: Richardson
mesh_terms: D000465:Algorithms; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000009:adverse effects*; D015331:Cohort Studies; D016099:Endoscopy, Gastrointestinal; D005260:Female; D005767:Gastrointestinal Diseases / Q000139:chemically induced* / Q000175:diagnosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D041742:Upper Gastrointestinal Tract
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal