Classification of chronic obstructive pulmonary disease severity according to the new Global Initiative for Chronic Obstructive Lung Disease 2011 guidelines: COPD assessment test versus modified Medical Research Council scale

Abstract

Introduction: The GOLD2011 revision proposes to stratify patients with chronic obstructive pulmonary disease (COPD) by measuring the impact of the disease using the modified Medical Research Council (mMRC) scale or COPD assessment test (CAT). Our aim was to determine whether both methods are equivalent.

Patients and methods: Observational study on a cohort of 283 patients diagnosed with COPD. We analyzed the demographic and lung function results. Patients were assessed by CAT and mMRC on the same day by the same interviewer, and divided into GOLD2011 categories according to the result of the evaluation. The degree of concordance and Spearman correlation were determined. We used ANOVA on the clinical and functional variables of the four GOLD2011 categories.

Results: Assessing the classification of patients according to the method used, an overall correlation ρ=0.613 and a degree of concordance κ=0.63 (moderate) were obtained. κ=0.44 was obtained for the 152 patients in categoriesA and B (moderate-low), and 0.38 for the 131 patients in categoriesC and D (low). Differences were observed between categories in terms of functional parameters.

Conclusions: The classification of patients with COPD using the assessment proposed by GOLD2011 varies according to the method used (CAT or mMRC); more than 25% of patients were reclassified into different categories, implying differences in the recommended therapeutic strategy. Longitudinal studies are needed to appraise which method better classifies patients, according to its prognostic ability.

Keywords: Categorización; Chronic obstructive pulmonary disease; Classification; Concordance; Concordancia; Correlación; Correlation; Cuestionarios; Enfermedad pulmonar obstructiva crónica; Questionnaires.