The COPD Assessment Test and the modified Medical Research Council scale are not equivalent when related to the maximal exercise capacity in COPD patients

Abstract

<b>Background:</b> The management and treatment of the Chronic Obstructive Pulmonary Disease (COPD) are based on a cutoff point either of ≥ 10 on the COPD Assessment Test (CAT) or of ≥ 2 of the Medical Research Council (mMRC). Up to now, no study has assessed the equivalence between CAT and mMRC, as related to the exercise tolerance in COPD. <b>Aims and objectives:</b> The aim of the study was to evaluate in COPD patients the relationship between CAT and mMRC and maximal exercise capacity and the agreement between CAT (≥ 10) and the mMRC (≥ 2) to categorize the patients according to the exercise tolerance. <b>Methods:</b> 118 consecutive COPD patients (39 females), aged between 47 and 85 years with a wide range of airflow obstruction and lung hyperinflation were studied. Maximal exercise capacity was assessed by the cardiopulmonary exercise test. <b>Results:</b> CAT and mMRC scores were significantly related to VO₂ peak (p&lt;0.01). CAT (≥ 10) and mMRC (≥ 2) have a high likelihood to be associated to a value of VO₂ peak less than 15.7 and 15.6 mL/kg/min, respectively. The interrater agreement between CAT (≥ 10) and mMRC (≥ 2) was found to be fair (κ = 0.20) in all patients and slight, when they were subdivided in those with VO₂ peak &lt; 15 mL/kg/min and in those with VO₂ peak ≥ 15 mL/kg/min (κ = 0.10 and κ = 0.20 respectively). <b>Conclusion:</b> This study shows that CAT and mMRC are useful tools to predict exercise tolerance in COPD, but they cannot be considered as supplementary measures.