COPD
-
Simple walking tests are widely used for the assessment of functional status in patients with cardiorespiratory disorders. These tests require far less instrumentation than formal cardiopulmonary exercise tests, but they do require standardization of procedures to achieve reproducible results. The most widely used tests for patients with COPD are the 6-minute walking test (6MWT) and the incremental shuttle walking test (SWT). ⋯ The SWT results improve with pulmonary rehabilitation and bronchodilation, and are highly correlated with maximum oxygen consumption. There are no studies that address the issue of MCID for the SWT. In addition to the MCID, the design and interpretation of COPD clinical trials should take into account the severity of initial impairment, the asymmetry between positive and negative changes, the proportion of patients who show substantial improvement, and the costs and risks of the treatment.
-
The Minimal Clinically Important Difference has become a key feature for both the validation of clinical tools and for the assessment of clinical studies. Several methods have been developed to establish what a Minimal Clinically Important Difference is. The primary purpose of the Minimal Clinically Important Difference, however, is to provide a measure of relevance for a statistically applied measure. ⋯ Conversely, parameters that are of great interest to selected individuals, that could be discerned by them with great subtly are likely to be poorly generalizable. Without doubt, defining a Minimal Clinically Important Difference will remain a key goal in the validation and application of tools for clinical investigations. The limits of the concept, particularly as it relates to issues of importance to patients, however, needs to be recognized.
-
Dyspnea is a primary symptom of chronic lung disease and an important outcome measure for clinical trials. Several standardized measures have been developed to evaluate this important symptom and are being used increasingly in clinical trials. ⋯ The analysis is based on a retrospective review of published trials evaluating the response to a pulmonary rehabilitation or exercise intervention that is known to produce modest, but clinically meaningful changes for such patients. Using a distribution-based approach based primarily on effect size, the recommended MCID for these measures are: 5-units for the SOBQ, 1-unit for the Borg scale, and approximately 10 to 20 units for the VAS.
-
Limitation of physical activity occupies a central role in the symptom complex of patients with chronic obstructive pulmonary disease (COPD), and improvement in exercise capacity is a key outcome of response to COPD therapy. Maximum exercise capacity testing facilitates assessment of physiologic mechanisms of exercise and allows quantitation of the degree of limitation. This manuscript utilizes published data from the National Emphysema Treatment Trial to investigate the minimal clinically important difference (MCID) in maximum exercise capacity in patients with severe emphysema. ⋯ In subjects randomized to medical therapy, the mean (+/-SD) 24-month change in maximum exercise capacity following medical therapy was -9.2 +/- 1.2 Watts, whereas among those randomized to lung volume reduction surgery, mean 24-month change in maximum exercise capacity was 1.7 +/- 17.7 Watts, with a mean difference between the groups of 10.9 Watts. The observed difference in maximum exercise capacity after 24 months between subjects randomized to medical versus surgical therapy conforms to both opinion- and distribution-based estimates of MCID. Further investigation is needed to develop and validate estimates of MCID for maximum exercise capacity and other key clinical outcomes in COPD.