Comparisons of health status scores with MRC grades in COPD: implications for the GOLD 2011 classification

The 2011 Global Initiative for Chronic Obstructive Lung Disease (GOLD) strategy document recommends assessment of chronic obstructive pulmonary disease (COPD) using symptoms and future exacerbation risk, employing two score cut-points: COPD Assessment Test (CAT) score >= 10 or modified Medical Research Council dyspnoea scale (mMRC) grade >= 2. To explore the equivalence of these two symptom cut-points, the relationship between the CAT and the mMRC and St George's Respiratory Questionnaire (SGRQ), the Short-form Health Survey and the Functional Assessment of Chronic Illness Therapy Fatigue scores were retrospectively analysed using a primary care dataset. Data from 1817 patients (mean +/- SD forced expiratory volume in 1 s 1.6 +/- 0.6 L) showed a significant association between mMRC grades and all health status scores (ANOVA p < 0.0001). mMRC grade 1 was associated with significant levels of health status impairment (SGRQ 39.4 +/- 15.5 and CAT 15.7 +/- 7.0); even patients with mMRC grade 0 had modestly elevated scores (SGRQ 28.5 +/- 15.1 and CAT 11.7 +/- 6.8). An mMRC grading >= 2 categorised 57.2% patients with low symptom (groups A and C) versus 17.2% with the CAT. Using the mMRC cut-point (>= 1) resulted in similar GOLD group categorisations as the CAT (18.9%). The mMRC showed a clear relationship with health status scores; even low mMRC grades were associated with health status impairment. Cut-points of mMRC grade >= 1 and CAT score >= 10 were approximately equivalent in determining low-symptom patients. The GOLD assessment framework may require refinement.