Vascular Quality of Life Questionnaire-6 facilitates health-related quality of life assessment in peripheral arterial disease

Abstract

Background: Most commonly used outcome measures in peripheral arterial disease (PAD) provide scarce information about achieved patient benefit. Therefore, patient-reported outcome measures have become increasingly important as complementary outcome measures. The abundance of items in most health-related quality of life instruments makes everyday clinical use difficult. This study aimed to develop a short version of the 25-item Vascular Quality of Life Questionnaire (VascuQoL-25), a PAD-specific health-related quality of life instrument.

Methods: The study recruited 129 individuals with intermittent claudication and 71 with critical limb ischemia from two university hospitals. Participants were a mean age of 70 ± 9 years, and 57% were men. All patients completed the original VascuQoL when evaluated for treatment, and 127 also completed the questionnaire 6 months after a vascular procedure. The VascuQoL-25 was reduced based on cognitive interviews and psychometric testing. The short instrument, the VascuQoL-6, was tested using item-response theory, exploring structure, precision, item fit, and targeting. A subgroup of 21 individuals with intermittent claudication was also tested correlating the results of VascuQoL-6 to the actual walking capacity, as measured using global positioning system technology.

Results: On the basis of structured psychometric testing, the six most informative items were selected (VascuQoL-6) and tested vs the original VascuQoL-25. The correlation between VascuQoL-25 and VascuQoL-6 was r = 0.88 before intervention, r = 0.96 after intervention, and the difference was r = 0.91 (P < .001). The Cronbach α for the VascuQoL-6 was .85 before and .94 after intervention. Cognitive interviews indicated that the responders considered all six items to be relevant and comprehensible. Rasch analysis was used to reduce response options from seven (VascuQoL-25) to four (VascuQoL-6). VascuQol-6 was shown to have high precision and discriminative properties. Item fit was excellent, with both "infit" and "outfit" between 0.7 and 1.3 for all six items. The standardized response mean after intervention was 1.15, indicating good responsiveness to clinical change. VascuQoL-6 results correlated strongly (r = 0.72; P < .001) with the actual measured walking ability (n = 21).

Conclusions: VascuQoL-6 is a valid and responsive instrument for the assessment of health-related quality of life in PAD. The main advantage is the compact format that offers a possibility for routine use in busy clinical settings.