Introduction The revised 2013 Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines propose a composite assessment and drug treatment according to exacerbation risk and symptoms (into category A, B C or D). It is unclear how muscle weakness and exercise capacity relate to these categories, however, pulmonary rehabilitation is proposed for groups B, C and D. We wished to quantify the frequency of these deficits in the GOLD composite assessment categories.
Methods A cohort of secondary care chronic obstructive pulmonary disease (COPD) patients in the United Kingdom and The Netherlands has been previously described (Eur Respir J. 2010;36:81–8). Using previously reported lower limits of normal, patients with quadriceps maximum voluntary contraction (QMVC) weakness and/or reduced six-minute walking test (SMWT) performance, were retrospectively identified in this cohort. Patients were divided into the revised GOLD combined assessment categories using spirometry and Medical Research Council (MRC) dyspnoea score. Phenotypes were further compared with self-reported medication use.
Results The original cohort comprised 351 patients (mean (SD) age 63(10) years), 59% males) with measured spirometry and quadriceps maximum voluntary contraction strength. Table 1 shows frequency of QMVC weakness and reduced SMWT performance in the different combined GOLD assessment categories. The majority of patients (58%) were in the most severe category (D). There was no statistical difference in the frequency of quadriceps weakness between categories. Reduced SMWT performance differed significantly between categories (Chi-square P < 0.001). Reduced SMWT performance was less common than muscle weakness in category A (P = 0.025). Logistic regression suggested that normal (preserved) quadriceps strength and SMWT performance were associated with long-acting beta agonist (LABA) use (OR 1.99, 95% CI 1.02 to 3.88, P = 0.043, and OR 2.00, 95% CI 1.01 to 4.00, P = 0.049 respectively), independent of assessment category and other COPD medication.
Discussion GOLD assessment category A may contain individuals who would benefit from pulmonary rehabilitation. Quadriceps weakness was more common than reduced walking capacity in this category. Exacerbation history and COPD assessment test (CAT) score were not recorded in this cohort and may have produced different results. A prospective investigation of LABA use on exercise capacity and muscle strength in COPD may be indicated.