Background/Purpose: Calcium pyrophosphate disease (CPPD) commonly affects elderly patients, but few advances in our management of this disease have occurred in the 50 years since it was first described.  Progress has been hampered by the absence of large population-based studies of CPPD.  The National Veterans Administration (VA) system would be an ideal location to perform such studies. However,  the accuracy of the diagnostic codes for CPPD in this database have not been confirmed.  We set out to determine the accuracy of International Classification of Disease (ICD) codes for  pseudogout/other disorders of calcium metabolism (275.49) and chondrocalcinosis (712.1-712.39) for the diagnosis of CPPD  in a single VA hospital database and to describe the clinical picture of this disease in the VA population.

Methods: After approval by the IRB, 256 patients identified as having CPPD by ICD-9 codes for chondrocalcinosis (712.1-712.39) and pseudogout/other disorders of calcium metabolism (275.49) were identified at the Clement J. Zablocki VA Medical Center in Milwaukee, WI for the years 2009-2011.  A chart review was performed by a second year rheumatology fellow for each patient and patients were categorized as having definite, probable, possible CPPD or no evidence of CPPD based on the diagnostic criteria proposed by McCarty and Ryan. Other data collected included patient demographics, the number and type of joints involved, whether the patients had been seen by the VA rheumatology service, and co-morbidities including renal disease and diabetes.

Results: Based on the medical records review , 227/256 (88.6%) patients met criteria for CPPD.    Of these, 46 patients met definite criteria, 163 met probable criteria, and 18 met possible criteria for CPPD.  Of these 227 patients, 107 (47.1%) patients had ICD-9 code 275. Seventy three (32.1%) had ICD-9 code 712, and 47 (20.7%) had both codes documented.  The average age was 73.28 years (range 32-94 years), and, consistent with VA demographics in this age cohort, 98.2 % were men.  Sixty-one (26.8%) had stage III or greater chronic kidney disease and 79 (34.8%) had diabetes.  Many patients had both acute and chronic arthritis, as 166 (73.1%) had at least one documented episode of acute arthritis, while 208 (91.6%) had chronic articular symptoms.  Knee involvement occurred in 86 patients, followed in frequency by involvement of the hand (68), wrist (64), foot ( 35), ankle (34), elbow (20), and olecranon bursa (10).  The average number of joints involved for patients with chronic arthritis was 2.35 (range 1-6) and for acute was 2.012 (range 1-6).  Rheumatology had evaluated 51.5% of these patients, including 83% with definite CPPD, 43.6% with probable CPPD, and 44.4% with possible CPPD.

Conclusion: We found a high correlation between evidence of CPPD documented in medical records and the ICD codes 275.49 and 712 in the medical records database at a single VA medical center.  The demographics of this population and pattern of joint involvement confirm prior studies of the epidemiology of this disease and further support the accuracy of these codes.  These findings suggest that the national VA healthcare database may be useful for future clinical studies of CPPD.

---

« Back to 2012 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/accuracy-of-international-classification-of-disease-codes-for-calcium-pyrophosphate-disease-in-the-veterans-adminstration-healthcare-system/