Preliminary validation of the Claudication Symptom Instrument (CSI)

This article describes the development of the Claudication Symptom Instrument (CSI) and its measurement properties for evaluating the symptom experience of patients diagnosed with intermittent claudication (IC). We conducted semi-structured qualitative interviews with IC patients for item development and cognitive interviews in which patient comprehension of items was tested. We evaluated measurement properties using data collected and analyzed in the context of an observational comparative effectiveness study of IC treatments. Items measuring five symptom important to patients were developed and cognitively tested: Pain, Numbness, Heaviness, Cramping, and Tingling. Item means (higher means worse) ranged from 1.1 (Tingling) to 2.3 (Pain) (range: 0 'none' to 4 'extreme'). Rasch analysis yielded support for an overall score (χ²=26.5, df=20, p=0.15). The total CSI score differed by clinician-rated severity of mild versus moderate ( p<0.05), but not moderate versus severe. Re-administration of the CSI 5-10 days after baseline yielded an intra-class correlation coefficient of 0.86. Changes in CSI total score and VASCUQOL total score between baseline and 6 months post-treatment were correlated at -0.52 ( p<0.05). The CSI preliminarily meets accepted measurement standards for content validity, internal consistency and test-retest reliability, construct validity, and sensitivity for detecting change. Because of its high test-retest reliability, it may also be useful in clinical care with individual patients. It takes approximately 3 minutes to complete.