Usefulness of the Medical Research Council (MRC) dyspnoea scale as a measure of disability in patients with chronic obstructive pulmonary disease

Background-Methods of classifying chronic obstructive pulmonary disease (CO PD) depend largely upon spirometric measurements but disability is only wea kly related to measurements of lung function. With the increased use of pul monary rehabilitation, a need has been identified for a simple and standard ised method of categorising disability in COPD. This study examined the val idity of the Medical Research Council (MRC) dyspnoea scale for this purpose . Methods-One hundred patients with COPD were recruited from an outpatient pu lmonary rehabilitation programme. Assessments included the MRC dyspnoea sca le, spirometric tests, blood gas tensions, a shuttle walking test, and Borg scores for perceived breathlessness before and after exercise. Health stat us was assessed using the St George's Respiratory Questionnaire (SGRQ) and Chronic Respiratory Questionnaire (CRQ). The Nottingham Extended Activities of Daily Living (EADL) score and Hospital Anxiety and Depression (HAD) sco re were also measured. Results-Of the patients studied, 32 were classified as having MRC grade 3 d yspnoea, 34 MRC grade 4 dyspnoea, and 34 MRC grade 5 dyspnoea. Patients wit h MRC grades 1 and 2 dyspnoea were not included in the study. There was a s ignificant association between MRC grade and shuttle distance, SGRQ and CRQ scores, mood state and EADL. Forced expiratory volume in one second (FEV1) was not associated with MRC grade. Multiple logistic regression showed tha t the determinants of disability appeared to vary with the level of disabil ity. Between MRC grades 3 and 4 the significant covariates were exercise pe rformance, SGRQ and depression score, whilst between grades 4 and 5 exercis e performance and age were the major determinants. Conclusions-The MRC dyspnoea scale is a simple and valid method of categori sing patients with COPD in terms of their disability that could be used to complement FEV1 in the classification of COPD severity.