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We aimed to investigate the construct validity of the Timed Up & Go (TUG) test in chronic obstructive pulmonary disease (COPD), to identify characteristics related to an abnormal TUG time and to examine the responsiveness of the TUG to pulmonary rehabilitation (PR). TUG time was assessed before and after comprehensive PR in 500 COPD patients, and compared cross-sectionally in 100 non-COPD subjects. Physical health outcomes, mental health outcomes, symptom-related outcomes and multidimensional indices were assessed in COPD patients only. Good convergent and discriminant validity was demonstrated by fair-to-moderate correlation with physical health outcomes, symptom-related outcomes and multidimensional indices ( r = 0.18-0.70) and by little correlation with mental health outcomes ( r = 0.21-0.26). COPD patients had a worse TUG time than non-COPD subjects, demonstrating known-groups validity. A TUG time of 11.2 seconds had good sensitivity (0.75) and specificity (0.83) for identifying patients with a baseline 6-minute walk distance <350 m. TUG time improved after PR ( p < 0.0001) and a change of 0.9-1.4 seconds was identified as clinically important. The TUG is valid and responsive in COPD. An abnormal result is indicative of poor health outcomes. This simple test provides valuable information and can be adopted in clinical and research settings.

IntroductionChronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality. Patients with COPD are characterised by a reduced health status, which can be easily assessed by the COPD Assessment Test (CAT). Previous studies show that health status can be worsened by the presence of comorbidities. However, the impact of cardiovascular comorbidities on health status as assessed with CAT is not sufficiently investigated. Therefore, the current study has the following objectives: (1) to study the clinical, (patho)physiological and psychosocial determinants of the CAT, and impact of previously established and/or newly diagnosed cardiovascular comorbidities on health status in tertiary care patients with COPD; (2) to assess the effects of pulmonary rehabilitation on CAT scores in patients with COPD; (3) to develop reference values for the CAT in Dutch elderly patients without COPD; and (4) to validate the CAT in a broad sample of Dutch patients with COPD.Methods and analysisThe COPD, Health status and Comorbidities (Chance) study is a monocentre study consisting of an observational cross-sectional part and a longitudinal part. Demographic and clinical characteristics will be assessed in primary care, secondary care and tertiary care patients with COPD, and in patients without COPD. To assess health status, the CAT, Clinical COPD Questionnaire (CCQ) and St George's Respiratory Questionnaire (SGRQ) will be used. The longitudinal part consists of a comprehensive pulmonary rehabilitation programme in 500 tertiary care patients. For the cross-sectional part of the study, 150 patients without COPD, 100 primary care patients and 100 secondary care patients will be assessed during a single home visit.Ethics and disseminationThe Medical Ethical Committee of the Maastricht University Medical Centre+ (MUMC+), Maastricht, the Netherlands (METC 11-3-070), has approved this study. The study has been registered at the Dutch Trial Register (NTR 3416).

The application of these new cut-points would reclassify about one-third of the patients with COPD and, thus, would impact on individual disease management. Further validation in prospective studies of these new values are needed.

Mild-to-moderate AEs do not affect dropout or response of PR, although severe AEs are associated with dropout. AEs should not lead to discontinuation of PR, as response is in general not affected.