Positive predictive value of sarcoidosis identified in an administrative healthcare registry: a validation study.

BACKGROUND International classification of disease (ICD) codes used to study sarcoidosis have previously been validated in only one study. We aimed to determine the accuracy of ICD codes to identify true sarcoidosis diagnoses in Sweden. METHODS We identified adults with at least two ICD codes for sarcoidosis (ICD-10 D86) at Karolinska University Hospital 2010-2013 from the National Patient Register. Of these, we randomly sampled 100 patients for validation. We collected clinical data and categorized the diagnosis of sarcoidosis as definite, probable, or unlikely. We estimated the positive predictive value (PPV) for definite and probable sarcoidosis -- identified with at least two ICD codes -- with 95% confidence intervals (CI). RESULTS We deemed 77% of the cases to be definite and 17% to be probable. The PPV was 0.94 (95% CI 0.87, 0.98). CONCLUSIONS Using at least two visits listing an ICD-10 code for sarcoidosis accurately identified patients with sarcoidosis from administrative health data in Sweden.