title: Validity of diagnostic codes and prevalence of psoriasis and psoriatic arthritis in a managed care population, 1996-2009.
abstract: BACKGROUND
  Few population-based studies have reported the prevalence of psoriatic disease.
  
  
  OBJECTIVE
  We validated computerized diagnoses to estimate the prevalence of psoriasis and psoriatic arthritis.
  
  
  METHODS
  We identified adults with ≥1 ICD-9 diagnosis codes of 696.0 (psoriatic arthritis) or 696.1 (psoriasis) in clinical encounter data during 1996-2009 and used chart review to confirm the diagnoses in random samples of patients. We then used the best performing case-finding algorithms to estimate the point prevalence of psoriasis and psoriatic arthritis.
  
  
  RESULTS
  The number of persons with a diagnosis for psoriasis (ICD-9 code 696.1) was 87 827. Chart review of a random sample of 101 cases with at least one dermatologist-rendered psoriasis code revealed a positive predictive value (PPV) of 90% (95% CI, 83-95) with sensitivity of 88% (95% CI, 80-93). Psoriatic arthritis (code 696.0) was recorded for 5187 patients, with the best performing algorithm requiring ≥2 diagnoses recorded by a rheumatologist or ≥1 diagnosis recorded by a rheumatologist together with ≥1 psoriasis diagnoses recorded by a dermatologist; the PPV was 80% (95% CI, 70-88) with sensitivity 73% (95% CI, 63-82). Among KPNC adults, the point prevalence of psoriasis, with or without psoriatic arthritis, was 939 (95% CI, 765-1142) per 100 000, and the overall prevalence of psoriatic arthritis, with or without psoriasis, was 68 (95% CI, 54-84) per 100 000.
  
  
  CONCLUSIONS
  Within an integrated health care delivery system, the use of computerized diagnoses rendered by relevant disease specialists is a valid method for identifying individuals with psoriatic disease.
authors: Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA.
authors: Maryam M
authors: MM
authors: Asgari
authors: Jashin J
authors: JJ
authors: Wu
authors: Joel M
authors: JM
authors: Gelfand
authors: Craig
authors: C
authors: Salman
authors: Jeffrey R
authors: JR
authors: Curtis
authors: Leslie R
authors: LR
authors: Harrold
authors: Lisa J
authors: LJ
authors: Herrinton
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D015535:Arthritis, Psoriatic / Q000175:diagnosis / Q000453:epidemiology*; D059019:Clinical Coding; D019033:Delivery of Health Care, Integrated; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D008329:Managed Care Programs; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D011565:Psoriasis / Q000175:diagnosis / Q000453:epidemiology*; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: computerized medical information; epidemiology; incidence, prevalence, health maintenance organizations; pharmacoepidemiology; psoriasis; psoriatic arthritis
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