Identifying COPD patients with poor health status and low exercise tolerance through the five-repetition sit-to-stand test and modified Medical Research Council Dyspnea Score

Abstract

Background: The objective of this study was to determine whether the concomitant presence of poor health status (COPD Assessment Test, CAT ≥ 10 points) and low exercise tolerance (6-Minute Walking Test, 6MWT < 350 m) is associated with worse clinical characteristics in patients with COPD. In addition, we aimed to develop a readily applicable diagnostic model to discriminate COPD patients with these conditions. Methods: A cross-sectional multicenter study involving 208 stable COPD patients (FEV1/FVC < 0.7, smoking history of at least 10 pack-years, and chronic respiratory symptoms) was carried out. The outcome measures were the 6MWT, CAT score, 5-repetition sit-to-stand test (5STS) and modified Medical Research Council Dyspnea Scale (mMRC). Patients were categorized into three groups: no condition (6MWT ≥ 350 m and CAT < 10 points), one condition (6MWT < 350 m or CAT ≥ 10 points), and both conditions (6MWT < 350 m and CAT ≥ 10 points). Results: A total of 26 patients (12,5%) presented both conditions. These patients experienced a higher degree of dyspnea (p = 0.001), smoking pack-years (p = 0.011), severe obstruction (p = 0.006), and time on 5STS (p = 0.001). The probability of having both conditions directly increased with the time spent on the 5STS (β=0.188; p = 0.010) and the degree of dyspnea (β=1.920; p < 0.001) (R2=0.413). The scoring system, using the 5STS and dyspnea as surrogate measures, demonstrated adequate calibration between the predicted and observed risk (linear R2=0.852). Conclusions: COPD patients with concurrent conditions have worse clinical status. The diagnostic model developed to discriminate these patients shows good internal validation.