title: Validation of administrative codes for calcium pyrophosphate deposition: a Veterans Administration study.
abstract: BACKGROUND
  Despite high prevalence, progress in calcium pyrophosphate deposition (CPPD) has been limited by poor awareness and absence of validated approaches to study it in large data sets.
  
  
  OBJECTIVE
  We aimed to determine the accuracy of administrative codes for the diagnosis of CPPD as a foundational step for future studies.
  
  
  METHODS
  We identified all patients with an International Classification of Diseases, Ninth Revision, Clinical Modification code for chondrocalcinosis (712.1-712.39) or pseudogout/other disorders of mineral metabolism (275.49), and convenience sample selected a comparison group with gout (274.00-03 or 274.8-9), or rheumatoid arthritis (714.0) from 2009 to 2011 at a Veterans Affairs medical center. Each patient was categorized as having definite, probable, or possible CPPD or absence of CPPD based on the McCarty and Ryan criteria using chart abstracted data including crystal analysis, radiographs, and arthritis history.
  
  
  RESULTS
  Two hundred forty-nine patients met the clinical gold standard criteria for CPPD based on medical records, whereas 48 patients met definite criteria, 183 probable, and 18 met possible criteria. The accuracy of administrative claims with a code of 712 or 275.49 for definite or probable CPPD was as follows: 98% sensitivity (95% confidence interval, 96%-99%), 78% specificity (74%-83%), 91% positive predictive value, and 94% negative predictive value.
  
  
  CONCLUSIONS
  At this center, single administrative code 275.49 or 712 accurately identifies patients with CPPD with a positive predictive value of 91%. These findings suggest that administrative codes can have strong clinical accuracy and merit further validation to allow adoption in future epidemiologic studies of CPPD.
authors.affiliation: From the *Division of Rheumatology, Department of Medicine, University of Wisconsin, and William S. Middleton VA Medical Center, Madison, WI; †Birmingham Veterans Affairs Medical Center and ‡Division of Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; and §Division of Rheumatology, Department of Medicine, Medical College of Wisconsin; and ∥Clement J. Zablocki VA Medical Center, Milwaukee, WI.
authors.forename: Christie M
authors.initials: CM
authors.lastname: Bartels
authors.forename: Jasvinder A
authors.initials: JA
authors.lastname: Singh
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Parperis
authors.forename: Karri
authors.initials: K
authors.lastname: Huber
authors.forename: Ann K
authors.initials: AK
authors.lastname: Rosenthal
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002805:Chondrocalcinosis / Q000145:classification* / Q000175:diagnosis*; D016208:Databases, Factual; D005260:Female; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D014481:United States; D014493:United States Department of Veterans Affairs