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.