With the increased use of data from electronic medical records for research, it is important to validate International Classification of Diseases, Ninth Revision (ICD-9) codes for their respective diagnoses.
To assess the accuracy of using ICD-9 codes to identify ocular inflammatory diseases.
Design, Setting, and Participants
Retrospective secondary database analysis. The setting was Kaiser Permanente Hawaii, an integrated managed care consortium that serves approximately 15% of the general Hawaiian population. Participants were patients with ICD-9 diagnosis codes that might be associated with a diagnosis of ocular inflammation seen at Kaiser Permanente Hawaii between January 1, 2006, and December 31, 2007. The data collection and analysis took place from January 2011 to August 2015.
Main Outcomes and Measures
The main outcome was the positive predictive value (PPV) of ICD-9 codes for identifying specific types of ocular inflammatory disease. The PPVs were calculated by determining the ratio of the confirmed cases found by medical record review to the total number of cases identified by ICD-9 code.
Of the 873 patients identified by a comprehensive list of ICD-9 codes for ocular inflammatory diseases, 224 cases were confirmed as uveitis after medical record review. Using a set of uveitis-specific codes and eliminating patients with a history of ocular surgery, the overall PPV for uveitis was 61% (95% CI, 56%-66%). The PPVs for individual uveitis codes ranged from 0% to 100%, and 11 uveitis codes had a PPV exceeding 80%. Herpes zoster ophthalmicus and scleritis/episcleritis ICD-9 codes had PPVs of 91% (95% CI, 86%-95%) and 60% (95% CI, 54%-66%), respectively.
Conclusions and Relevance
Our results suggest that using ICD-9 codes alone to capture uveitis and scleritis/episcleritis diagnoses is not sufficient in the Kaiser Permanente Hawaii healthcare system, although there were specific uveitis codes with high PPVs. However, the electronic medical record can reliably be used to identify herpes zoster ophthalmicus cases. Medical record review, as was done in this study, is recommended to elucidate diagnoses for uveitis and scleritis/episcleritis.