Numerous measures are available for evaluating chronic obstructive pulmonary disease (COPD) patients, covering areas such as functional status, health status, cognition, emotions, balance, and exercise, to name a few. This series, “Practical Respiratory Disease Outcome Measures…,” attempts to fill a gap for the clinician and investigator, by offering them the tools to assess and report clinically meaningful information. Three articles anchor this series, the first by Houchen and Evans, “The Minimum Important Differences-Pearls and Pitfalls when Applying to Practical Outcome Measures,” describes the minimal clinically important difference (MCID). The MCID provides clinical meaningfulness to data and a context for interpreting the clinical application of research. The importance of this article lies in the fact that there is often false confidence in study results, when the “p” value is significant. This article will describe how the MCID is calculated and why this calculated figure should be weighed when interpreting clinical data. The MCID can provide more robust evidence beyond the “statistically important difference” in understanding the clinical meaning of results. MCIDs, however, have not been calculated for all instruments and all disease states and interventions, as seen in the two subsequent articles.
Lareau and Blackstock, in “Functional Status Measures for the COPD Patient: A Practical Categorization,” provides a comprehensive review of these physical activity measures. In this article, the reader will see the variety and complexity of measurement options related to functional status measures (FSMs). Over 61 were reported in the respiratory literature; however, only 35 were reviewed that had been tested beyond the original development or used in the past decade in the COPD population. To assist the potential user of FSMs make sense of these numerous measures, they categorized the instruments by their commonalities. Each of the FSMs is described according to the number of actual activities performed, scoring, time required to complete the instrument, psychometric properties particularly in the COPD population (including the MCID when available), and caveats regarding the original reason for the development of the FSM and reports the relationship of each measure (when known) to other measures; for example, the correlation of the FSM with exercise capacity.
In a relatively new area of assessment that is critically important to function is balance. In COPD patients, balance issues are magnified resulting in a high risk for falling. The article by Beauchamp, “Balance Measurement in People with COPD: An Evidence-Based Guide,” describes the range of instruments available in the area of evaluating a patient’s balance, from basic screening measures to comprehensive assessment. These measures will aid the clinician by providing simple, but reliable measures of evaluating balance risks. For research purposes or to guide the physiotherapist in providing care, more in-depth evaluations are reviewed. Over 60 standing balance tests are available, but similar to FSMs, not all have strong measurement properties or tested in the respiratory disease population.
The goal of this series is to arm both the clinician and the researcher with the tools by which they can evaluate studies and identify the strength and weaknesses of various measurement instruments.