Measurement of walking endurance and walking velocity with questionnaire: Validation of the walking impairment questionnaire in men and women with peripheral arterial disease

Objectives: The Walking Impairment Questionnaire (WIQ) was designed to measure community walking ability in patients with peripheral arterial disease (PAD) and intermittent claudication. We compared the WIQ scores to objective measures of walking in a heterogeneous group of patients with and without PAD. Methods: The study was designed as a cross-sectional study, with the setting in an academic medical center. The subjects were patients with PAD (n = 145) who were identified from a noninvasive vascular laboratory at an academic medical center. The patients without PAD (n = 65) were identified from a general medicine practice. The average number of comorbidities was 2.03 for patients with PAD and 1.52 for patients without PAD. Among the patients with PAD, 28% had classical intermittent claudication symptoms and 55% had exertional leg symptoms other than claudication. The main outcome measures were the WIQ estimates of the patient-reported walking distance and walking speed on a scale of 0 to 100. Walking endurance was measured objectively with the 6-minute walk. Walking velocity was measured with a 4-m walk. PAD and PAD severity were defined with the ankle brachial index. Results: The Spearman rank correlation coefficients (rho) between the WIQ distance score and the 6-minute walk score were 0.557 among patients with PAD (P < .001) and 0.484 among patients without PAD (P < .001). The correlation coefficients between the WIQ speed score and the usual-paced 4-m walk score were 0.528 among patients with PAD (P < .001) and 0.524 among patients without PAD (P < .001). The correlations were not affected by the presence versus the absence of intermittent claudication, by PAD severity, or by the presence of 2 or more versus less than 2 comorbid illnesses. The WIQ scores in the highest and lowest quartiles were the most closely associated with the objective measures of function. Conclusion: The WIQ is a valid measure of community walking ability in a heterogeneous group of patients with and without PAD. The WIQ discriminates best among patients in the highest and the lowest quartiles of walking speed and endurance.