title: Validation of an ICD-9-based claims algorithm for identifying patients with chronic idiopathic/spontaneous urticaria.
abstract: BACKGROUND
  There is no specific International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code for chronic idiopathic urticaria or spontaneous urticaria (CIU/CSU), a skin condition characterized by hives and angioedema lasting at least 6 weeks with no known cause.
  
  
  OBJECTIVE
  To validate an ICD-9-CM-based algorithm for identification of patients with CIU/CSU and thus facilitate claims-based research.
  
  
  METHODS
  Patient records were reviewed at 4 US practices. Patients included in the study were from a random sample of those identified by their physician as having CIU/CSU or because they met the following diagnosis-based algorithm: (1) at least 2 outpatient ICD-9-CM diagnosis codes 708.1, 708.8, or 708.9 at least 6 weeks apart or (2) 1 outpatient diagnosis of 708.1, 708.8, or 708.9 and 1 diagnosis of 995.1 at least 6 weeks apart. Data collected included ICD-9-CM codes, diagnoses of urticaria and allergy-related conditions, and medication use. Sensitivity and positive predictive value were calculated. The study was approved by the Western Institutional Review Board.
  
  
  RESULTS
  One hundred forty-nine patient records were reviewed (mean age 41.1 years; 73.8% were women; 69.1% were white): 115 were identified with the diagnosis-based algorithm, 90 were patients with "known CIU/CSU", and 56 were in the 2 groups. The mean duration of CIU/CSU was 2.9 to 3.1 years. The 2 cohorts most frequently had diagnoses of idiopathic urticaria, unspecified urticaria, and other specified urticaria. The diagnosis-based algorithm had a positive predictive value of 90.4% and a sensitivity of 71.1%.
  
  
  CONCLUSIONS
  The high positive predictive value suggests that patients identified using the algorithm are highly likely to have CIU/CSU. The 71.1% sensitivity suggests that most patients with CIU/CSU will be identified. The validation statistics support the use of the diagnosis-based algorithm in claims-based research, although future studies could refine the algorithm further.
authors.affiliation: Partnership for Health Analytic Research, LLC, Beverly Hills, California.
authors.forename: Dasha
authors.initials: D
authors.lastname: Cherepanov
authors.affiliation: Genentech Inc, South San Francisco, California. Electronic address: raimundo.karina@gene.com.
authors.forename: Karina
authors.initials: K
authors.lastname: Raimundo
authors.affiliation: Partnership for Health Analytic Research, LLC, Beverly Hills, California.
authors.forename: Eunice
authors.initials: E
authors.lastname: Chang
authors.affiliation: Partnership for Health Analytic Research, LLC, Beverly Hills, California.
authors.forename: Marianne
authors.initials: M
authors.lastname: Eagan
authors.affiliation: Genentech Inc, South San Francisco, California.
authors.forename: James L
authors.initials: JL
authors.lastname: Zazzali
authors.affiliation: Genentech Inc, South San Francisco, California.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Solari
authors.affiliation: Ocean Allergy and Respiratory Research Center, Brick, New Jersey.
authors.forename: Bruce
authors.initials: B
authors.lastname: DeCotiis
authors.affiliation: Allergy, Asthma and Immunology Center, PC, Vital Prospects Clinical Research Institute, Tulsa, Oklahoma.
authors.forename: Iftikhar
authors.initials: I
authors.lastname: Hussain
authors.affiliation: Asthma & Allergy Center, Toledo, Ohio.
authors.forename: Syed Maseeh
authors.initials: SM
authors.lastname: Rehman
authors.affiliation: Asthma & Allergy Center, Toledo, Ohio.
authors.forename: Nada
authors.initials: N
authors.lastname: Shahab
authors.affiliation: ASTHMA, Inc, Clinical Research Center, Seattle, Washington.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Tilles
authors.affiliation: Partnership for Health Analytic Research, LLC, Beverly Hills, California.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Broder
mesh_terms: D000328:Adult; D000465:Algorithms; D002908:Chronic Disease; D005260:Female; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D011237:Predictive Value of Tests; D014581:Urticaria / Q000145:classification*