AbstractBackground and ObjectiveElectronic medical record (EMR) databases can facilitate epidemiology research in various diseases including bronchiectasis. Given the diagnostic challenges of bronchiectasis, the validity of the coding in EMR requires clarification. We aimed to assess the validity of International Classification of Diseases, 9th Revision (ICD‐9) code algorithms for identifying bronchiectasis in the territory‐wide electronic medical health record system of Clinical Data Analysis and Reporting System (CDARS) in Hong Kong.Materials and MethodsAdult patients who had the diagnosis of bronchiectasis input from Queen Mary Hospital in 2011–2020 were identified using the ICD‐9 code of 494 by CDARS. All patients who had high resolution computed tomography (HRCT) were reviewed by respiratory specialists to confirm the presence of bronchiectasis on HRCT.ResultsA total of 19 617 patients who had the diagnostic code of bronchiectasis among all public hospitals in Hong Kong and 1866 in Queen Mary Hospital in the same period. Six hundred and forty‐eight cases were randomly selected and validated using medical record and HRCT review by a respiratory specialist. The overall positive predictive value (PPV) was 92.7% (95% CI 90.7–94.7).ConclusionsThis was the first ICD‐9 coding validation for bronchiectasis in Hong Kong CDARS. Our study demonstrated that using ICD‐9 code of 494 was reliable to support utility of CDARS database for further clinical research on bronchiectasis.