The MRC breathlessness scale

The symptom of breathlessness is a common feature of both respiratory and cardiac problems and is subjective and difficult to quantify thereby causing problems for researchers wanting to assess interventions and compare treatments. In order to develop a measure of the effect of breathlessness on everyday life, data which had been collected from studies on pneumoconiosis in Welsh coal miners were used to develop a series of questions about the disability resulting from breathlessness [1]. This was then developed into the familiar Medical Research Council (MRC) breathlessness/dyspnoea scale and was published in 1959 [2]. A respiratory questionnaire has also been developed by the MRC and is published along with guidance for interviewers, the latest version being published in 1986 [3]. The respiratory questionnaire was specifically designed for large epidemiological studies of between 100 and 1000 patients and is explicitly not for individual use [3].

Occupational Medicine last reviewed the MRC breathlessness scale including its historical development 8 years ago [4]. Since then it has continued to be extensively used in clinical research and practice, often in combination with other instruments which measure breathlessness. In its modified form, the questionnaire has more recently been used beyond respiratory conditions to include other system disorders such as obesity [5].

Scoring and interpretation

The scale on the original MRC dyspnoea scale is very simple, consisting of just five items containing statements about the impact of breathlessness on the individual and leading to a grade from 1 to 5. It can be self-administered or with a slight change in format of questions, delivered by a researcher or clinician. Either way it takes seconds to complete.

In the self-administered format, the patient selects the option that best describes their breathlessness as it affects their function. It does not grade breathlessness itself but the functional impact of breathlessness and perceived limitations that result. The grading is outlined in Table 1.

Clinical usage and performance

The use of the MRC breathlessness scale either on its own or in combination with other measures is widespread across the world in many scientific studies. The instrument allows stratification of populations to assess the effectiveness of interventions. An example is in pulmonary rehabilitation.

Researchers such as Bestall et al. [6] have explored its validity in this context. They found that the scale was a simple and valid method which could be used to categorize patients with chronic obstructive pulmonary disease (COPD) in terms of their disability and it could be used to complement forced expiratory volume in 1 s (FEV₁) in the classification of the severity of disease.

While much of the recent use of the MRC dyspnoea scale is in COPD patients, its performance in patients with idiopathic pulmonary fibrosis [7] and sarcoidosis [8] has also been documented. The original MRC breathlessness scale is currently recommended for use in the diagnosis of patients with COPD by government bodies such as NICE (National Institute for Health and Care Excellence in England) [9] and the modified version is a key feature of the GOLD 2011 (Global Initiative for Chronic Obstructive Airways Disease) recommend ations on assessment. In a study by Jones et al. [10], the modified MRC (mMRC) dyspnoea scale showed a clear relationship with health status scores and even low mMRC scores were associated with health impairment (Table 2).

Modifications

The mMRC breathlessness scale ranges from grade 0 to 4. It is very similar to the original version and is now widely used in studies.

It should be noted that the MRC clearly states on its website that it is unable to give permission for use of any modified version of the scale (including therefore, the mMRC scale) [3]. Use of the MRC questionnaire is free but should be acknowledged.

Comparisons

The MRC and mMRC scales are just two of many scales used in respiratory research. Chhabra et al. [11] compared three dyspnoea scales in COPD and found that the grades of dyspnoea on the mMRC were moderately interrelated with the Baseline Dyspnoea Index (BDI) and the Oxygen Cost Diagram (OCD) but the mMRC did not correlate with physiological impairment while the other two instruments did. This study, however, only considered patients with three of the five MRC grades. Other work by Camargo et al. [12] showed correlation with other instruments. In clinical studies, as opposed to clinical practice, some researchers, usually in the USA, tend to rely on the BDI but they need to be aware that although related to similar factors causing breathlessness, the BDI and mMRC score report the dyspnoea intensity in COPD patients differently and are not interchangeable [13]. The mMRC scale is often used with the Borg scale of perceived exertion [14] and the use of several scales including mMRC dyspnoea scale to assess COPD disability [14], evaluate quality of life [15] and provide tailored therapy [16] has been supported across the world [4,15,16].

References