Introduction
Chronic bronchitis and emphysema are common phenotypes of chronic obstructive pulmonary disease (COPD). Given the significant burden of COPD worldwide, a significant number of research studies have been conducted in large-scale population-level electronic healthcare records (EHRs) to provide robust findings to solve public health problems.1 In studies using EHRs, medical codes and codelists are used to identify diseases, symptoms, medicines, and procedures of interest.2 Different coding systems are used in primary and secondary care. Common coding systems include systematized nomenclature of medicine – clinical terms (SNOMED CT), international classification of diseases (ICD), and Read codes. Clinical diagnoses or drugs can be coded in different ways, depending on the code systems used. Some code…