title: Validation of coding algorithms for the identification of patients hospitalized for alcoholic hepatitis using administrative data.
abstract: BACKGROUND
  Epidemiologic studies of alcoholic hepatitis (AH) have been hindered by the lack of a validated International Classification of Disease (ICD) coding algorithm for use with administrative data. Our objective was to validate coding algorithms for AH using a hospitalization database.
  
  
  METHODS
  The Hospital Discharge Abstract Database (DAD) was used to identify consecutive adults (≥18 years) hospitalized in the Calgary region with a diagnosis code for AH (ICD-10, K70.1) between 01/2008 and 08/2012. Medical records were reviewed to confirm the diagnosis of AH, defined as a history of heavy alcohol consumption, elevated AST and/or ALT (<300 U/L), serum bilirubin >34 μmol/L, and elevated INR. Subgroup analyses were performed according to the diagnosis field in which the code was recorded (primary vs. secondary) and AH severity. Algorithms that incorporated ICD-10 codes for cirrhosis and its complications were also examined.
  
  
  RESULTS
  Of 228 potential AH cases, 122 patients had confirmed AH, corresponding to a positive predictive value (PPV) of 54% (95% CI 47-60%). PPV improved when AH was the primary versus a secondary diagnosis (67% vs. 21%; P < 0.001). Algorithms that included diagnosis codes for ascites (PPV 75%; 95% CI 63-86%), cirrhosis (PPV 60%; 47-73%), and gastrointestinal hemorrhage (PPV 62%; 51-73%) had improved performance, however, the prevalence of these diagnoses in confirmed AH cases was low (29-39%).
  
  
  CONCLUSIONS
  In conclusion the low PPV of the diagnosis code for AH suggests that caution is necessary if this hospitalization database is used in large-scale epidemiologic studies of this condition.
authors.affiliation: Liver Unit, Division of Gastroenterology and Hepatology, University of Calgary, Calgary, AB, Canada. jxpang@ucalgary.ca.|Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada. jxpang@ucalgary.ca.
authors.forename: Jack X Q
authors.initials: JX
authors.lastname: Pang
authors.affiliation: Liver Unit, Division of Gastroenterology and Hepatology, University of Calgary, Calgary, AB, Canada. erin.ross@albertahealthservices.ca.
authors.forename: Erin
authors.initials: E
authors.lastname: Ross
authors.affiliation: Liver Unit, Division of Gastroenterology and Hepatology, University of Calgary, Calgary, AB, Canada. mborman@ucalgary.ca.
authors.forename: Meredith A
authors.initials: MA
authors.lastname: Borman
authors.affiliation: Medical Services, Alberta Health Services, Calgary, AB, Canada. scott.zimmer@albertahealthservices.ca.
authors.forename: Scott
authors.initials: S
authors.lastname: Zimmer
authors.affiliation: Liver Unit, Division of Gastroenterology and Hepatology, University of Calgary, Calgary, AB, Canada. ggkaplan@ucalgary.ca.|Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada. ggkaplan@ucalgary.ca.
authors.forename: Gilaad G
authors.initials: GG
authors.lastname: Kaplan
authors.affiliation: Liver Unit, Division of Gastroenterology and Hepatology, University of Calgary, Calgary, AB, Canada. sjheitma@ucalgary.ca.|Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada. sjheitma@ucalgary.ca.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Heitman
authors.affiliation: Liver Unit, Division of Gastroenterology and Hepatology, University of Calgary, Calgary, AB, Canada. swain@ucalgary.ca.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Swain
authors.affiliation: Liver Unit, Division of Gastroenterology and Hepatology, University of Calgary, Calgary, AB, Canada. kwburak@ucalgary.ca.|Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada. kwburak@ucalgary.ca.
authors.forename: Kelly W
authors.initials: KW
authors.lastname: Burak
authors.affiliation: Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada. hquan@ucalgary.ca.
authors.forename: Hude
authors.initials: H
authors.lastname: Quan
authors.affiliation: Liver Unit, Division of Gastroenterology and Hepatology, University of Calgary, Calgary, AB, Canada. rpmyers@ucalgary.ca.|Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada. rpmyers@ucalgary.ca.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Myers
mesh_terms: D000328:Adult; D000416:Alberta / Q000453:epidemiology; D000465:Algorithms; D001201:Ascites / Q000175:diagnosis / Q000453:epidemiology; D059019:Clinical Coding; D016208:Databases, Factual / Q000592:standards*; D004812:Epidemiologic Methods; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000175:diagnosis / Q000453:epidemiology; D006519:Hepatitis, Alcoholic / Q000175:diagnosis* / Q000453:epidemiology*; D006801:Humans; D016247:Information Storage and Retrieval / Q000379:methods*; D038801:International Classification of Diseases; D008103:Liver Cirrhosis / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D010351:Patient Discharge; D011237:Predictive Value of Tests; D015995:Prevalence; D012189:Retrospective Studies