The intermittent claudication questionnaire: a patient-assessed condition-specific health outcome measure

INTRODUCTION: As yet, there is no patient-assessed, condition-specific instrument for the assessment of health-related quality of life in intermittent claudication. We evaluated the intermittent claudication questionnaire (ICQ) for properties required of a measure of health outcome. METHODS AND RESULTS: Interviews with patients with intermittent claudication and vascular specialist opinion produced a pool of statements used to itemize a self-completed ICQ. This was piloted in 20 patients for practicality and then administered to 124 stable claudicants. Reliability was assessed through a retest in 63 (51%) patients at 14 days and analysis of Cronbach's alpha for internal consistency. Spearman's correlation coefficient was used to assess construct validity in comparisons between the ICQ and ankle brachial pressure index, treadmill-walking distances, the walking impairment questionnaire, the EuroQol, and the Short Form-36. Responsiveness of the ICQ to changes in health was assessed in 60 patients treated conservatively and 40 patients undergoing angioplasty. The standardized response mean was used to identify the most responsive instrument in the study. A 16-item ICQ with a test-retest intraclass correlation of 0.95 and Cronbach's alpha of.94 was produced. One hundred twenty-one (98%) patients completed the ICQ (mean time, 3.7 minutes). The ICQ correlated better with the EuroQol (r = 0.58) and 7 out of 8 subscales of the Short Form-36 (r = 0.33-0.68) compared with the walking impairment questionnaire. The ICQ demonstrated the largest standardized response mean in relation to health transition compared with the other instruments. CONCLUSIONS: The patient-assessed ICQ is a practical, reliable, valid, and responsive measure of patient health-related quality of life in intermittent claudication.