mMRC (Modified Medical Research Council) Dyspnea Scale

Why Use

Easy and efficient to calculate. Provides a baseline assessment of functional impairment attributable to dyspnea from respiratory disease. Correlates with healthcare-associated quality of life, morbidity, and possibly mortality for patients with respiratory diseases (particularly COPD). Has been used for almost two decades in multiple different heterogeneous patient populations. Correlates with other clinical and research dyspnea indices. Inter-rater reliability is very high.

When to Use

Patients with respiratory diseases, to assess degree of baseline functional disability due to dyspnea.

Formula

Pearls / Pitfalls

The mMRC Dyspnea Scale quantifies disability attributable to breathlessness, and is useful for characterizing baseline dyspnea in patients with respiratory diseases. Describes baseline dyspnea, but does not accurately quantify response to treatment of chronic obstructive pulmonary disease (COPD). Does not capture patient effort, such that dyspnea from pulmonary disease (and not behavioral responses to disability) are reflected in mMRC Dyspnea Scale scores. Does not consistently correlate with spirometric measurements (e.g. FEV₁) for patients with respiratory disease due to COPD. Demonstrates at least moderate positive correlation with other dyspnea scores, including the baseline dyspnea index (BDI) and oxygen cost diagram (OCD) ( Chhabra 2009 ). At least moderately correlated with healthcare-associated quality of life, particularly for patients with COPD ( Henoch 2016 ). Scores are variably associated with patients’ perceptions of respiratory symptom burden or disease severity ( Rennard 2002 ). Scores are associated with morbidity (hospitalization and adverse cardiovascular outcomes) and, in some studies, mortality. Used as a component of the BODE Index , which predicts adverse outcomes, including mortality and risk of hospitalization ( Celli 2004 ).

Management

While measuring mMRC Dyspnea Scale scores in patients with respiratory disease (particularly COPD) to establish baseline functional dyspnea burden is appropriate, mMRC scores are not independently used in clinical practice to guide clinical management or therapeutic interventions. However, the Global Initiative for Obstructive Lung Disease (GOLD) treatment guidelines have, since 2011, included the mMRC as a component of a multi-faceted assessment and treatment approach to patients with COPD. A patient’s mMRC Dyspnea Scale score, or another dyspnea measurement, such as the COPD Assessment Test (CAT), is combined with the patient’s FEV₁ percent predicted and the frequency of COPD exacerbations to guide treatment interventions

Critical Actions

The mMRC Dyspnea Scale score must be contextualized with an individual patient’s history, physical, and available diagnostic test results. For patients with a higher mMRC grade (e.g. ≥2) and clinical circumstances consistent with respiratory disease, measuring spirometry (e.g., FEV₁ and FVC), determining the patient’s BODE Index and/or GOLD stage, and pursuing further targeted diagnostic and/or therapeutic interventions is appropriate.

Advice

The mMRC Dyspnea Scale is best used to establish baseline functional impairment due to dyspnea attributable to respiratory disease; tracking the mMRC over time or with therapeutic interventions is of less certain clinical utility. Furthermore, while the mMRC is correlated with morbidity and mortality for patients with respiratory disease, currently-available data do not confirm attributable cause and effect between mMRC Dyspnea Scale scores and patient-centered outcomes.

More Information

Interpretation: Higher grade indicates higher severity.