Measurement properties of the Patient-Reported Outcomes Information System (PROMIS® ) Itch Questionnaire: itch severity assessments in adults with atopic dermatitis

Abstract

Background: Little is known about the validity of numeric rating scales (NRS) and verbal rating scales (VRS) for itch and itch frequency for assessing itch severity in atopic dermatitis (AD). We evaluated the Patient-Reported Outcomes Information System (PROMIS^® ) Itch Questionnaire (PIQ) - itch severity assessment, including multiple NRS, VRS and frequency of itch assessments, in adults with AD and compared their performance.

Methods: Self-administered questionnaires and skin examinations were performed in 410 patients with AD (aged 18-90 years) in a dermatology practice setting.

Results: PIQ NRS, VRS and frequency of itch had good content validity, strong correlations with one another (Spearman correlations P < 0·001) and weak-to-moderate correlations with patient-oriented eczema measure (POEM), Eczema Area and Severity Index (EASI), objective SCORing AD (SCORAD) and Dermatology Life Quality Index (DLQI) (P < 0·001) and very good discriminant validity. Changes from baseline in NRS, VRS and frequency of itch were moderately to strongly correlated with one another, and weakly to moderately correlated with other patient-reported (POEM, SCORAD itch, DLQI) and clinician-reported outcomes (EASI, objective SCORAD). NRS and VRS worst itch and average itch showed moderate-to-good test-retest reliability. There were no floor or ceiling effects for NRS or VRS itch, but there were ceiling effects for itch frequency. Each assessment was completed in < 1 min by all patients.

Conclusions: NRS, VRS and frequency of itch items from PIQ - itch severity showed good content and construct validity, reliability, and/or responsiveness in adults with AD, and were feasible for use in clinical trials and practice. What is already known about this topic? Numeric rating scales (NRS), verbal rating scales (VRS) and frequency of itch have been used to assess the burden of itch. However, there have been limited results demonstrating their validity, responsiveness, interpretability and feasibility, particularly in atopic dermatitis (AD). What does this study add? This study demonstrated that NRS, VRS and frequency of itch items from the Patient-Reported Outcomes Information System (PROMIS^® ) Itch Questionnaire (PIQ) - itch severity assessments had good construct validity, responsiveness, reliability and feasibility in the assessment of adult AD. PIQ NRS, VRS and frequency of itch all appear to have sufficient validity, reliability and feasibility for use as assessments of itch in adults with AD in clinical practice and trials. What are the clinical implications of this work? PIQ NRS and VRS are all simple, valid, reliable and feasible for use in clinical practice and trials to assess itch in adults with AD. Linked Comment: Oosterhaven. Br J Dermatol 2020; 183:802-803.