A Systematic Review of Codelists to Identify Chronic Bronchitis and Emphysema in Routine Electronic Healthcare Record...

Medical codes and codelists are essential to identify diseases, medicines, and related events when using electronic healthcare records (EHRs) for research. As multiple codes can be used to define the same medical condition, an inconsistency of applying codes by clinicians or researchers may complicate the identification of diseases. To minimize the inconsistency of codes and increase the comparability of research findings, we sought to integrate all medical codes and codelists generated from existing studies to produce a single list of codes for both chronic bronchitis and emphysema for future research. We systematically reviewed studies, which included codes used to define chronic bronchitis and/or emphysema regardless of code systems. We searched MEDLINE, Embase, Web of Science, Scopus, CINAHL, and Global Health from 1^st January 2000 to May 2024 for relevant studies. Medical codes or codelists were identified, extracted, and compiled into single codelists for chronic bronchitis and emphysema separately based on their frequency of appearance across all included studies (PROSPERO: CRD42024529169). We identified 18 studies containing codelists, from a total of 1082 studies. Only International Classification of Disease (ICD) codes were found in studies, which defined chronic bronchitis and emphysema. Chronic bronchitis was defined as 490 and 491 in ICD-9 and J40, J41, J42, and J44 in ICD-10. Meanwhile, emphysema was defined as 492 in ICD-9 and J43 in ICD-10. Additionally, to fill the current gap, we created SNOMED CT codelists for both chronic bronchitis and emphysema, to standardize the definitions of these diseases in future studies.