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Eduardo Uchiyama, Sepideh Faez, Humzah Nasir, Sebastian H Unizony, George N Papaliodis, Lucia Sobrin; Accuracy of the International Classification of Diseases, 9th Revision (ICD-9) as a research tool for the identification of patients with polymyalgia rheumatica and concurrent noninfectious uveitis. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5592.
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To report the accuracy of the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes in a hospital-based database for for identifying patients with polymyalgia rheumatica (PMR) and concurrent noninfectious uveitis.
IRB approval for database queries and chart review was obtained. Multiple queries for patients with PMR (ICD-9-CM code 725.00) and all types of uveitis (anterior, intermediate, posterior, and panuveitis) were executed in the database of two large, general teaching hospitals using the Research Patient Data Registry (RPDR). Patients with infectious uveitis or other rheumatologic conditions were excluded. Patients who suffered from both PMR and concurrent ocular inflammatory disease were identified. The medical records of these patients were reviewed to confirm if the ICD-9 codes listed reflected the actual conditions described in the chart.
The RPDR query produced 10697 patients with the ICD-9 code for PMR and 4154 patients with ICD-9 codes for noninfectious uveitis. The number of patients with both PMR and noninfectious uveitis by ICD-9 codes was 66. Upon detailed review of medical records of these 66 patients, 31 actually had a clinical diagnosis of PMR, 37 actually had noninfectious uveitis, and only 19 had PMR with concurrent noninfectious uveitis. The patients who did not actually have the clinical diagnosis indicated by their ICD-9 code often had nonspecific joint pains or other causes of red eye instead of PMR and uveitis, respectively.
While the use of ICD-9 codes has been validated for medical research of common diseases, our results suggest ICD-9 codes may be of limited value for epidemiological investigations of rarer diseases which can be more difficult to diagnose. The ICD-9 codes for two rarer diseases, PMR and uveitis, did not reflect the true clinical problem in a large proportion of patients in this study.
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