Clinical validation of the Walking Impairment Questionnaire in patients with peripheral arterial disease: defining high and low walking performance values

Abstract

Objective: The validity of the Walking Impairment Questionnaire (WIQ) as a clinical tool for use by clinicians in the conservative management of patients with peripheral arterial disease (PAD) has not been well established. The objective of this study was to determine the validity of the WIQ as a tool to identify high and low walking ability (performance) in patients with PAD. Methods: We conducted a cross-sectional study and enrolled 132 new and existing PAD patients who consecutively attended the vascular clinic at Kingston General Hospital between May 2010 and May 2011. Patients with an Ankle Brachial Index ≤0.9 were approached for study inclusion. Participants were excluded if they had (a) severe ischemia requiring intervention; (b) comorbid conditions that limited walking (angina, congestive heart failure, chronic obstructive pulmonary disease or severe arthritis); (c) wheel chair, cane or walker requirement; (d) non-compressible arteries; and/or (e) severe cognitive impairment. Walking performance was assessed with the Walking Impairment Questionnaire (surrogate measure) and a standardized graded treadmill test (gold standard measure). Other study variables were obtained via questionnaire (age, sex, comorbid conditions and smoking status) or direct measurement (weight, height, waist circumference). Results: 123 patients completed the treadmill test (70.7% males, mean age of 66.5 and mean ABI of 0.6 with range 0-0.9). The scores on the WIQ ranged from 0 to 100 and absolute claudication distance (ACD) ranged from 0.03 to 0.98 miles. All WIQ subscale and overall scores were positively and moderately associated with the ACD (r values 0.63 to 0.68, p<0.05). Based on the area under the curve of the receiver operating characteristics curve analysis, an overall WIQ score of 42.5 or less identified low performers (sensitivity 0.9, specificity 0.7, area under the curve 0.89) while a combined distance and stair score of 75.5 or more identified high performers (sensitivity 0.4, specificity 0.9, area under the curve 0.81). Conclusions: Based on these findings, the WIQ, an easily administered self-report questionnaire, and the cutoffs identified could be used to quantify and classify walking ability in PAD patients, making this a potentially useful tool for clinicians to manage PAD patients.