title: The utility of administrative data for surveillance of comorbidity in multiple sclerosis: a validation study.
abstract: BACKGROUND
  Although comorbidity is important in multiple sclerosis (MS), few validated methods for its assessment exist. We validated and applied administrative case definitions for several comorbidities in MS.
  
  
  METHODS
  Using provincial administrative data we identified persons with MS and a matched general population cohort. Case definitions for chronic lung disease (CLD), epilepsy, inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and migraine were developed using administrative data, and validated against medical records. We applied these definitions to estimate the age-standardized prevalence of these comorbidities in the MS and matched cohorts.
  
  
  RESULTS
  Versus medical records, administrative case definitions showed moderate agreement for CLD (ĸ = 0.41), migraine (ĸ = 0.51), and epilepsy (ĸ = 0.44), fair agreement for IBS (ĸ = 0.36) and could not be calculated for IBD (small sample size). The 2005 prevalence of CLD was similar in the MS (15.6%) and general populations (14.4%). The prevalence of the remaining comorbidities was higher in the MS than the general populations: epilepsy (4.12 vs. 1.12%), IBD (0.78 vs. 0.65%), IBS (12.2 vs. 6.80%) and migraine (23.0 vs. 16.5%).
  
  
  CONCLUSIONS
  Administrative data are valid for tracking CLD, epilepsy, and migraine in MS. The prevalence of epilepsy, IBD, IBS and migraine is increased in MS versus the general population.
authors.affiliation: Department of Internal Medicine, University of Manitoba, Winnipeg, Man., Canada. rmarrie@hsc.mb.ca
authors.forename: Ruth Ann
authors.initials: RA
authors.lastname: Marrie
authors.forename: Bo Nancy
authors.initials: BN
authors.lastname: Yu
authors.forename: Stella
authors.initials: S
authors.lastname: Leung
authors.forename: Lawrence
authors.initials: L
authors.lastname: Elliott
authors.forename: Patricia
authors.initials: P
authors.lastname: Caetano
authors.forename: Sharon
authors.initials: S
authors.lastname: Warren
authors.forename: Christina
authors.initials: C
authors.lastname: Wolfson
authors.forename: Scott B
authors.initials: SB
authors.lastname: Patten
authors.forename: Lawrence W
authors.initials: LW
authors.lastname: Svenson
authors.forename: Helen
authors.initials: H
authors.lastname: Tremlett
authors.forename: John
authors.initials: J
authors.lastname: Fisk
authors.forename: James F
authors.initials: JF
authors.lastname: Blanchard
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D002908:Chronic Disease; D015897:Comorbidity; D004827:Epilepsy / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology; D043183:Irritable Bowel Syndrome / Q000453:epidemiology*; D008171:Lung Diseases / Q000453:epidemiology*; D008297:Male; D008350:Manitoba / Q000453:epidemiology; D016347:Medical Records Systems, Computerized / Q000592:standards* / Q000706:statistics & numerical data; D008875:Middle Aged; D008881:Migraine Disorders / Q000453:epidemiology*; D009103:Multiple Sclerosis / Q000453:epidemiology*; D011159:Population Surveillance / Q000379:methods; D015995:Prevalence