Gait Speed: Validity of Measurement in Patients With Severe Chronic Lung Disease, Including Prognostic and Practical Implications.

Gait speed is used increasingly to predict function and future well-being among healthy elderly people as well as for those with long-term medical conditions. When selecting outcome measures such as walking speed, it is important to include the circumstances under which the measurement is made to avoid bias and ensure accurate recommendations. We completed a retrospective chart review of walking test results from patients with chronic lung disease to demonstrate the practical implications of reporting gait speed from either a standing or walking start. In this cohort of 99 patients (55 with COPD), gait speed from a standing start underestimated usual gait speed (difference = 6.1 m/min [5.3-6.9 m/min]) with poor agreement (8 m/min [6.6-9.4 m/min]) between the two methods of reporting speed. The standing start speed incorrectly identified some patients as at higher risk for poor health. In a practical example, gait speed from a standing start produced 11 false-negative evaluations of the ability to complete a road crossing at usual speed. We present walking speeds using both methods, which illustrate the importance of construct validity and measurement protocol.