Prevalence of overestimation or underestimation of the functional capacity using MRC score as compared to 6-minute walk test in patients with cardio-respiratory disorders

Abstract

Objectives: The first objective of our study was to assess whether patients diagnosed with cardio-respiratory disorders report overestimation or underestimation on recall (Medical Research Council (MRC) dyspnea scale) of their true functional capacity (walked distance during a 6-minute walk test (6MWT)). The second objective was to assess whether the measurement of breathlessness at the end of a 6MWT (Borg score) may help to identify dyspneic patients on recall. Methods: The 6MWTs of 746 patients aged from 40 to 80 years who were diagnosed with either chronic obstructive pulmonary disease (COPD, n = 355), diffuse parenchymal lung disease (n = 140), pulmonary vascular diseases (n = 188) or congestive heart failure (n = 63) were selected from a prospective Clinical Database Warehouse. Results: The percentage of patients who overestimated (MRC ≤ 2 with distance < lower limit of normal (LLN), 61/746, 8%; 95% confidence interval (CI): 6 to 10%) or underestimated (MRC > 2 with distance ≥LLN, 121/746, 16%; 95%CI: 14 to 19%) on recall their capacity was elevated. The overestimation seemed related to self-limitation, while the underestimation seemed related to patients who “work through” their breathing discomfort. These two latter groups of patients were mainly diagnosed with COPD. A Borg dyspnea score >3 (upper limit of normal) at the end of the 6MWT had 84% specificity for the prediction of a MRC score >1. Conclusion: Almost one fourth of patients suffering from cardio-pulmonary disorders overestimate or underestimate on recall their true functional capacity. An elevated Borg dyspnea score at the end of the 6MWT has a good specificity to predict dyspnea on recall.

Keywords: :

• activity-related dyspnea
• chronic obstructive pulmonary disease
• diffuse parenchymal lung disease
• pulmonary vascular disease
• chronic heart failure

Acknowledgments

The authors wish to thank the technicians of the pulmonary function laboratory for their expert assistance (Martine Riquelme, Françoise Genisty, Mireille Morot, Marien Bokouabassa) and the different contributors from the Department of Medical Informatics (DIM: Romain Chenu for database management and Christel Daniel for supervision (RE-USE project)).

The salary of Mrs. Chevalier-Bidaud was granted by the Assistance Publique –Hôpitaux de Paris (Direction de la Recherche Clinique et du Développement, director: Christophe Misse).

Declaration of Interest Statement

The authors declare the absence of conflict of interest.

All authors made 1) substantial contributions to conception and design (BM, CD2), acquisition of data (EC, LP, KGJ, ME), or analysis (BCB, RC, CD2) and interpretation of data (all authors); 2) drafting the article (EC, BM, CD2) or revising it critically for important intellectual content (KGJ, SG, BCB, RC, ME); and 3) final approval of the version to be published (all authors). CD2 is the guarantor of the entire manuscript.