Correlation Between COPD Assessment Test (CAT) Scores and the BODE Index in Stable Chronic Obstructive Pulmonary Disease (COPD): A Prospective Observational Study

Background Chronic obstructive pulmonary disease (COPD) remains a leading cause of global morbidity and mortality, yet its clinical assessment continues to rely heavily on spirometry, which inadequately reflects patient-centred disease burden. The need for rapid, scalable, and clinically meaningful assessment tools is particularly critical in resource-constrained settings. This study explores whether the COPD Assessment Test (CAT), a simple symptom-based instrument, correlates strongly with multidimensional prognostic indices such as the Body mass index, airflow Obstruction, Dyspnea, and Exercise capacity (BODE) index. Methods A prospective observational study was conducted on 60 stable COPD patients. Clinical, demographic, and exposure data, including smoking and biomass exposure, were systematically recorded. All patients underwent spirometry and assessment using the CAT score and the BODE index. Correlation analysis using Pearson’s coefficient was performed to evaluate relationships between the CAT score, BODE index, and forced expiratory volume in one second (FEV1)​​​​​​. Results The study cohort demonstrated a high burden of disease with predominant moderate-to-severe airflow limitation. Risk factor analysis revealed substantial exposure to both smoking and biomass fuels, reflecting real-world environmental contributions to COPD. Symptomatically, breathlessness and productive cough were highly prevalent, indicating advanced disease at presentation. A strong positive correlation was observed between CAT score and BODE index (r = 0.808, 95% CI: 0.69-0.89, R2 = 0.653, p < 0.001), suggesting close alignment between patient-reported outcomes and multidimensional disease severity. Additionally, the CAT score showed a strong inverse correlation with FEV1 (r = -0.729, 95% CI: -0.90 to -0.71, R2 = 0.687, p < 0.001), comparable to the relationship between the BODE index and FEV1 (r = -0.73, p < 0.001). These findings demonstrate that the CAT score captures both symptomatic and physiological dimensions of COPD. Conclusion This study demonstrates that the CAT score, a rapid and easily deployable tool, strongly correlates with the BODE index and spirometric severity. These findings suggest that CAT may complement comprehensive COPD assessment as a complementary screening tool, particularly in resource-limited healthcare settings. However, CAT should not be considered interchangeable with the BODE index, which captures additional dimensions such as body mass index and formal exercise capacity. Further validation in diverse populations is needed before routine clinical implementation.