Validity and reliability of itch assessment scales for chronic pruritus in adults: A prospective multicenter study

Abstract

Background: Several tools can provide a reliable and accurate evaluation of pruritus, including the visual analog scale (VAS), numeric rating scale (NRS), verbal rating scale (VRS), and multidimensional questionnaires such as the Itch Severity Scale (ISS). However, no single method is considered a gold standard. Objective: We evaluated the validity and reliability of VAS, NRS, VRS, and ISS and their correlation with a pruritus-specific quality of life instrument, ItchyQoL. Methods: A total of 419 patients (215 men and 204 women) with chronic pruritus (mean age, 46.58 years) recorded their pruritus intensity on VAS, NRS, VRS, and ISS. Retest reliability was analyzed in a second assessment 3 hours after the initial assessment. All participants answered ItchyQoL. Results: A strong correlation between VAS, NRS, and VRS was found. ISS showed a low intercorrelation validity with these tools. However, ISS was more strongly correlated with ItchyQoL. The retest reliability scores were similar for VAS, NRS, and VRS but lower than the scores obtained for ISS. Limitations: Limitations include patient heterogeneity and recall bias. Conclusion: The assessment of pruritus is challenging because of the subjective symptoms and the multifactorial nature. Therefore, more studies are needed to determine the best strategy to assess itch intensity.