A pilot quality-of-life instrument for pruritus.

ABSTRACT

OBJECTIVE: We sought to develop a validated, reliable pruritus-specific quality-of-life (QOL) instrument, ItchyQoL. METHODS: From 21 in-depth interviews with patients with pruritus, we developed 22 pruritus-specific items, and hypothesized 3 major constructs that explain the way pruritus affects patients' QOL symptoms, functional limitations, and emotions. We developed two versions of the pruritus QOL instrument, which assess for level of bother or frequency using items from the interviews and from generic skin QOL instruments, Skindex-16 (bother) and Skindex-29 (frequency). The instrument was tested for validity, reliability, and responsiveness. The frequency version was subsequently applied clinically to further evaluate its face validity. RESULTS: A total of 89 patients with dermatologic conditions participated in the validation phase and 101 patients participated in the clinical application phase of the study. Construct validity was demonstrated by principal axes factor analyses and by demonstrating that differences in symptoms, functioning, and emotion differed among the varying levels of self-reported pruritus severity more than would be expected by chance (P < .05 by analysis of variance). The instrument demonstrated reliability with internal consistency (Cronbach alpha frequency 0.72-0.93 and bother 0.78-0.81) and reproducibility (intraclass correlation coefficient frequency 0.91 and bother 0.84-0.87). The instrument suggested preliminary responsiveness for patients with improved disease for both frequency and bother items with both overall scores and the majority of the subscales scored demonstrating significant changes. Discriminant validity was shown by comparing differences in and the number of insensitive items between the pruritus-specific QOL instrument and the generic Skindex instruments. LIMITATIONS: Lack of generalizability and potential selection bias are limitations. CONCLUSIONS: This study represents, to our knowledge, the first attempt at a pruritus-specific QOL instrument that is reliable, valid, and responsive.