Clinical interpretation of the Uremic Pruritus in Dialysis Patients (UP-Dial) scale: a novel instrument for the assessment of uremic pruritus.

BACKGROUND: The Uremic Pruritus in Dialysis Patients (UP-Dial) scale is valid and reliable for uremic pruritus (UP) assessment. However, it remains unknown how the scores should be interpreted in clinical practices. OBJECTIVES: To establish a clinical interpretation of the UP-Dial by identifying severity cut-off scores according to the disease severity and burden of pruritus. METHODS: This cross-sectional study developed a classification system for the UP-Dial scores using the patient-based anchors method. From May 2012 through January 2017, 697 dialysis patients were screened. Of these, a total of 258 met the criteria for UP and completed the UP-Dial scale and three sets of patient-assessed anchor questions: (i) global UP intensity by visual analogue scale (VAS)-UP, (ii) Dermatology Life Quality Index and (iii) global kidney disease-related quality of life. The cut-off scores were generated based on the kappa (κ) coefficient of agreement and the area under receiver operating characteristic curve (AuROC) statistics. Subgroup analyses were performed to explore associations between patient characteristics and the UP-Dial severity bands. RESULTS: The proposed scores were ≤12 (mild), 13-21 (moderate) and ≥22 (severe) with κ coefficient ranging between 0.39 and 0.46. Assigned scores were associated with all patient-based anchors. The highest association was with the VAS-UP, and AuROC was 0.80 (mild; 95% CI, 0.75-0.86), 0.66 (moderate; 0.60-0.71) and 0.83 (severe; 0.77-0.89). In subgroup analysis according to patient characteristics, we did not find any significant difference. CONCLUSIONS: The estimated UP-Dial severity band can facilitate the interpretation of UP in practice-based research settings and can be used to support treatment decisions.

Development of a multidimensional assessment tool for uraemic pruritus: Uraemic Pruritus in Dialysis Patients (UP-Dial).

BACKGROUND: Dialysis patients with uraemic pruritus (UP) have significantly impaired quality of life. To assess the therapeutic effect of UP treatments, a well-validated comprehensive and multidimensional instrument needed to be established. OBJECTIVES: To develop and validate a multidimensional scale assessing UP in patients on dialysis: the Uraemic Pruritus in Dialysis Patients (UP-Dial). METHODS: The development and validation of the UP-Dial instrument were conducted in four phases: (i) item generation, (ii) development of a pilot questionnaire, (iii) refinement of the questionnaire with patient recruitment and (iv) psychometric validation. Participants completed the UP-Dial, the visual analogue scale (VAS) of UP, the Dermatology Life Quality Index (DLQI), the Kidney Disease Quality of Life-36 (KDQOL-36), the Pittsburgh Sleep Quality Index (PSQI) and the Beck Depression Inventory (BDI) between 15 May 2012 and 30 November 2015. RESULTS: The 27-item pilot UP-Dial was generated, with 168 participants completing the pilot scale. After factor analysis was performed, the final 14-item UP-Dial encompassed three domains: signs and symptoms, psychosocial, and sleep. Face and content validity were satisfied through the item generation process and expert review. Psychometric analysis demonstrated that the UP-Dial had good convergent and discriminant validity. The UP-Dial was significantly correlated [Spearman rank coefficient, 95% confidence interval (CI)] with the VAS-UP (0·76, 0·69-0·83), DLQI (0·78, 0·71-0·85), KDQOL-36 (-0·86, -0·91 to -0·81), PSQI (0·85, 0·80-0·89) and BDI (0·70, 0·61-0·79). The UP-Dial revealed excellent internal consistency (Cronbach's α 0·90, 95% CI 0·87-0·92) and reproducibility (intraclass correlation 0·95, 95% CI 0·90-0·98). CONCLUSIONS: The UP-Dial is valid and reliable for assessing UP among patients on dialysis. Future research should focus on the cross-cultural adaptation and translation of the scale to other languages.