Rationale: The challenge in studying chronic bronchitis (CB) is partly due to the inconsistent application of its definition across various research works. This study addresses the critical aspect of the Definition Of Compare by examining how different definitions impact patient identification and characterization.
Objectives: Our primary objective was to definition of compare an alternative definition of chronic bronchitis, utilizing the St. George’s Respiratory Questionnaire (SGRQ), against the traditional, or ‘classic,’ definition. We aimed to determine if this alternative SGRQ definition offered unique or complementary insights when juxtaposed with the established norm.
Methods: We conducted an analysis on a dataset encompassing 4,513 individuals categorized within Global Initiative for Chronic Obstructive Lung Disease (GOLD) groups 1 through 4, sourced from the COPDGene cohort. Our methodology involved a direct definition of compare between the classic CB definition and the SGRQ-based definition. The latter was formulated based on participant responses concerning both cough and phlegm within the SGRQ. We established two primary comparison groups: Classic CB positive (CB+) versus Classic CB negative (CB-), and SGRQ CB positive (CB+) versus SGRQ CB negative (CB-). Furthermore, to dissect the nuances of agreement and disagreement between definitions, we segmented the cohort into four distinct subgroups: Classic CB+/SGRQ CB+, Classic CB+/SGRQ CB-, Classic CB-/SGRQ CB+, and Classic CB-/SGRQ CB-.
Measurements and Main Results: Our findings indicated that 26.1% of the subjects met the criteria for Classic CB+, while a larger proportion, 39.9%, were classified as SGRQ CB+. When we performed a definition of compare of the SGRQ definition against the Classic CB definition—using the latter as our reference standard—the SGRQ definition demonstrated a sensitivity of 0.87 and a specificity of 0.77. Notably, the SGRQ CB+ and Classic CB+ groups exhibited striking similarities. Both groups presented with elevated respiratory symptom burden, increased frequency of exacerbations, diminished lung function, and greater airway wall thickness. Intriguingly, the subgroups displaying discordance between definitions—Classic CB+/SGRQ CB-, Classic CB+/SGRQ CB-, and Classic CB-/SGRQ CB+—also shared comparable characteristics with the concordant groups.
Conclusions: The SGRQ-based CB definition effectively identifies a broader patient population experiencing chronic cough and sputum production. These individuals share a phenotype that is notably similar to that delineated by the Classic CB definition. Therefore, in the context of definition of compare, incorporating the SGRQ CB definition alongside the classic definition offers a valuable approach to identify a greater number of patients with chronic obstructive pulmonary disease who are at heightened risk for adverse health outcomes. This refined approach to case definition enhances our ability to capture a more comprehensive spectrum of individuals in need of targeted interventions and care.
