The validity and reliability of four-meter gait speed test for stable interstitial lung disease patients: the prospective study

BACKGROUND: The 4-m gait speed test is a simple functional performance measure for older adults or patients with chronic obstructive lung disease. However, limited data exist regarding these measures for patients with interstitial lung disease. We evaluated the correlation between the 4-m gait speed and 6-min walk distance tests for interstitial lung disease patients and examined their underlying physiological factors. METHODS: The 4-m gait speed and 6-min walk tests were prospectively conducted for 51 patients with interstitial lung disease. Other measurements included health-related quality of life, modified Medical Research Council score, arterial blood gas levels, pulmonary function, muscle strength according to the skeletal muscle mass index and physical activity. RESULTS: Thirty-five patients were male (68.6%). Thirty-four patients had idiopathic pulmonary fibrosis (66.7%). There were significant correlations between the 4-m gait speeds and 6-min walk distances (r=0.57; P<0.001). Multivariate analyses showed that both the 4-m gait speed and 6-min walk distance were correlated with the modified Medical Research Council score. In addition, the 6-min walk distance was correlated with age and the percentage of the predicted diffusion capacity of carbon monoxide. CONCLUSIONS: The 4-m gait speed test is a simple, easy to perform and reliable functional performance measure for interstitial lung disease patients.