Comparison of the Determinants of the “Chronic Obstructive Pulmonary Disease Assessment Test” (CAT) and the “Asthma Control Test” (ACT) in Patients with Asthma–COPD Overlap

<b>Objective:</b> The objective of this study was to investigate which of two short questionnaires, the Asthma Control Test (ACT) or the COPD Assessment Test (CAT), correlates better with severity variables and whether they share similar determinants in patients with asthma-COPD overlap. <b>Method:</b> This observational, cross-sectional, multicentric study included smokers and former smokers of more than 10 pack-years, with non-fully reversible airflow obstruction and either a concomitant diagnosis of asthma or signs of type 2 inflammation, from 15 centres in Spain. <b>Results:</b> A total of 157 patients were included, 109 (69.4%) were men, the mean age was 63.3 (SD: 9) years and the mean FEV1 (%) was 59.7% (SD: 20.5%). The mean CAT score was 14.5 (SD: 8.7), and the mean ACT score was 17.9 (SD: 5.2). Both scores showed good correlations (r = 0.717; <i>p</i> < 0.001). In the multivariate analysis, the Hospital Anxiety and Depression Scale and mMRC dyspnoea scores were independently and significantly associated with both the CAT and ACT scores; however, age was only significantly associated with the CAT, and the EQ-5D scores and the number of exacerbations in the previous year were only significantly associated with the ACT scores. The ACT had a slightly better predictive value for exacerbations than the CAT (AUC = 0.70 (95% CI: 0.62 to 0.79 vs. 0.65 (95% CI: 0.56 to 0.74))). <b>Conclusions:</b> There is a good correlation between ACT and CAT scores in patients with ACO. However, severe patients scored worse on the CAT than the ACT. Anxiety, depression and dyspnoea were significantly associated with both the CAT and ACT scores. The ACT was a slightly better predictor of exacerbations than the CAT in this population.