Sheu MJ, et al. - This study intended to confirm the use of International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) codes to identify patients with chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infection in the Taiwan National Health Insurance (NHI) Outpatient Claims Dataset. A retrospective study was performed using the results of HBV surface antigen (HBsAg), HBV e antigen (HBeAg), and anti-HCV antibody tests in the NHI Lab & Exam Dataset from January 1 to March 31, 2018, as the reference standard to confirm HBV and HCV infection cases. Researchers estimated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) to assess the performance of HBV infection-specific ICD-10-CM codes (B180, B181, and B191) and HCV infection-specific ICD-10-CM codes (B182 and B192) recorded in the NHI Outpatient Claims Dataset to distinguish individuals with HBV or HCV infection. In this study, 196,635 and 120,628 patients had analyzable outcomes for HBsAg/HBeAg tests and anti-HCV tests, respectively. Physicians recorded the HBV and HCV infection-specific ICD-10-CM codes in Taiwan NHI outpatient claims data in 2018 had moderate sensitivity and high specificity for both HBV and HCV infection. For HCV ICD-10-CM codes, the PPV was high, yet moderate for HBV ICD-10-CM codes.