Usefulness of the Chronic Obstructive Pulmonary Disease Assessment Test to Evaluate Severity of COPD Exacerbations

Rationale: The Chronic Obstructive Pulmonary Disease (COPD) Assessment Test (CAT) is an eight-item questionnaire designed to assess and quantify the impact of COPD symptoms on health status. COPD exacerbations impair quality of life and are characterized by worsening respiratory symptoms from the stable state. We hypothesized that CAT scores at exacerbation relate to exacerbation severity as measured by exacerbation duration, lung function impairment, and systemic inflammation. Objectives: To evaluate the usefulness of the CAT to assess exacerbation severity. Methods: One hundred sixty-one patients enrolled in the London COPD cohort completed the CAT at baseline (stable state), exacerbation, and during recovery between April 2010 and June 2011. Measurements and Main Results: Frequent exacerbators had significantly higher baseline CAT scores than infrequent exacerbators (19.5 +/- 6.6 vs. 16.8 +/- 8.0, P = 0.025). In 152 exacerbations, CAT scores rose from an average baseline value of 19.4 +/- 6.8 to 24.1 +/- 7.3 (P < 0.001) at exacerbation. Change in CAT score from baseline to exacerbation onset was significantly but weakly related to change in C-reactive protein (rho = 0.26, P = 0.008) but not to change in fibrinogen (rho = 0.09, P = 0.351) from baseline to exacerbation. At exacerbation, rises in CAT score were significantly associated with falls in FEV1 (rho = 0.20, P = 0.032). Median recovery time as judged by symptom diary cards was significantly related to the time taken for the CAT score to return to baseline (rho = 0.42, P = 0.012). Conclusions: The CAT provides a reliable score of exacerbation severity. Baseline CAT scores are elevated in frequent exacerbators. CAT scores increase at exacerbation and reflect severity as determined by lung function and exacerbation duration.