Developing the Vascular Quality of Life Questionnaire: a new disease-specific quality of life measure for use in lower limb ischemia

Abstract

Aims: The purpose of this study was to develop and validate an easily used disease-specific quality of life (QOL) measure for patients with chronic lower limb ischemia and to design an evaluative instrument, responsive to within-subject change, that adds to clinical measures of outcome when comparing treatment options in the management of lower limb ischemia.

Methods: The first phase consisted of item generation, item reduction, formulating, and pretesting in patients with ischemia. The proportion of patients who selected an item as troublesome and the mean importance they attached to it were combined to give a clinical impact factor. Items with the highest clinical impact factor were used to formulate a new 25-item questionnaire that was then pretested in 20 patients with lower limb ischemia. In the second phase, reliability, validity, and responsiveness of the new questionnaire were assessed in 39 patients with lower limb ischemia who were tested at 0 and 4 weeks. The King's College Hospital's Vascular Quality of Life Questionnaire and the Short-Form 36 were administered at each visit, and treadmill walking distance and ankle/brachial pressure indices were recorded. The new questionnaire's reliability, internal consistency, responsiveness, and validity were determined.

Results: Areas of QOL impairment were consistent through the ranges of disease severity and age, with no apparent differences between the men and women. Therefore, a single questionnaire is applicable to all patients with chronic lower limb ischemia. In stable patients test-retest scores demonstrated a reliability of r more than 0.90. Each item had internal consistency (item-domain Cronbach alpha =.7-.9). The questionnaire was responsive to change, with correlation between change in the questionnaire's total score and both global and clinical indicators of change (P <.001). The questionnaire showed face and construct validity.

Conclusions: This disease-specific questionnaire is reliable, responsive, valid, and ready for use as an outcome measure in clinical trials. It is sensitive to the concerns of patients with lower limb ischemia, offering a simple method to measure the effect of interventions on their QOL.