Health Status Assessment in Routine Clinical Practice: The Chronic Obstructive Pulmonary Disease Assessment Test Score in Outpatients

BACKGROUND: The chronic obstructive pulmonary disease (COPD) assessment test (CAT) is a simple, self-completion questionnaire developed to measure health status in patients with COPD, which is potentially suitable for routine clinical use. OBJECTIVES: The purpose of this study was to establish the determinants of the CAT score in routine clinical practice. METHODS: Patients attending the clinic completed the CAT score before being seen. Clinical data, including, where available, plethysmographic lung volumes, transfer factor and arterial blood gas analysis, were recorded on a pro forma in the clinic. RESULTS: In 224 patients (36% female), mean forced expiratory volume in 1 s (FEV₁) was 40.1% (17.9) of predicted (%pred); CAT score was associated with exacerbation frequency 0-1/year 20.1 (7.6); 2-4/year 23.5 (7.8); >4/year 28.5 (7.3), p < 0.0001; 41/40/19% in each category and with Medical Research Council (MRC) dyspnoea score (r² = 0.26, p < 0.0001) rising approximately 4 points with each grade. FEV(1) %pred had only a weak influence. Using stepwise regression, CAT score = 2.48 + 4.12 MRC (1-5) dyspnoea score + 0.08 (FEV(1) %pred) + 1.06 (exacerbation rate/year)] (r² = 0.36, p < 0.0001). The CAT score was higher in patients (n = 54) with daily sputum production 25.9 (7.5) vs. 22.2 (8.2); p = 0.004. Detailed lung function (plethysmography and gas transfer) was available in 151 patients but had little influence on the CAT score. CONCLUSION: The CAT score is associated with clinically important variables in patients with COPD and enables health status measurement to be performed in routine clinical practice.