Modified Medical Research Council and COPD Assessment Test Cutoff Points.

Background: The modified Medical Research Council (mMRC) and COPD Assessment Test (CAT) are assessment instruments associated with level of physical activity of daily living (PADL) in patients with COPD. This study aimed to identify mMRC and CAT cutoff points to discriminate sedentary behavior and PADL level of subjects with COPD and verify whether these cutoff points differentiate pulmonary function, health-related quality of life (HRQOL), functional status, and mortality index in subjects with COPD.

Methods: Subjects ( 131, FEV: 36.7 ± 16.1% predicted) were assessed for lung function, mMRC, CAT, HRQOL, functional status, and mortality index. PADL was monitored using a triaxial accelerometer, and subjects were classified as sedentary/nonsedentary (cutoff point of 8.5 h/d in PADL < 1.5 metabolic equivalent of task [MET]), physically active/inactive (cutoff point of 80 min/d in PADL ≥ 3 METs), and with/without severe physical inactivity (cutoff point of 4,580 steps/d), according to variables provided by accelerometer.

Results: ROC curve indicated mMRC cutoff point of ≥ 2 ( < .05) for physical inactivity (sensitivity = 66%, specificity = 56%, AUC = 0.62), severe physical inactivity (sensitivity = 81%, specificity = 66%, AUC = 0.76), and sedentary behavior (sensitivity = 61%, specificity = 70%, AUC = 0.65). The identified CAT cutoff points were ≥ 16 and ≥ 20, considering severe physical inactivity (sensitivity = 76%, specificity = 54%, AUC = 0.69, < .001) and sedentary behavior (sensitivity = 51%, specificity = 90%, AUC = 0.71, = .001), respectively. Subjects who had mMRC ≥ 2 and CAT ≥ 16 or ≥ 20 presented worse pulmonary function, HRQOL, functional status, and mortality index compared with those who scored mMRC < 2 and CAT <16 or < 20.

Conclusions: mMRC cutoff point of ≥ 2 is recommended to discriminate PADL level and sedentary behavior, whereas CAT cutoff points of ≥ 16 and ≥ 20 discriminated severe physical inactivity and sedentary behavior, respectively. These cutoff points differentiated subjects with COPD regarding all the outcomes assessed in this study.