Psychometric Evaluation of the Multidimensional Scale-Uremic Pruritus in Dialysis Patients (UP-Dial): Comparison in Hemodialysis and Peritoneal Dialysis Patients with Chronic Pruritus.

ABSTRACT

BACKGROUND: High-quality patient-reported outcome (PRO) measures for dialysis patients with chronic pruritus are urgently needed. However, no known, well-validated multidimensional tools have been investigated to measure pruritus symptoms in dialysis patients. OBJECTIVES: To examine the psychometric properties of a multidimensional tool of chronic pruritus, the Uremic Pruritus in Dialysis (UP-Dial) 14-item, by comparing hemodialysis and peritoneal dialysis modality. METHODS: This validation study used data from the Thai Renal Outcomes Research-Uremic Pruritus, a prospective, multicenter, longitudinal study. Data for this study were collected from February 1, 2019, to May 31, 2022. The adult sample of 226 hemodialysis and 327 peritoneal dialysis patients fulfilled the criteria of chronic pruritus based on the International Forum for the Study of Itch. Psychometric properties of the UP-Dial included validity and reliability, as measured across hemodialysis and peritoneal dialysis patients. Patients completed a set of anchor-based measurement tools, including global itching, Dermatology Life Quality Index (DLQI), EuroQoL-5 dimension-5 level (EQ-5D-5L), Kidney Disease Quality of Life-36 (KDQOL-36), Pittsburgh Sleep Quality Index (PSQI), global fatigue, Somatic Symptom Scale-8 (SSS-8), and Patient Health Questionnaire-9 (PHQ-9). RESULTS: From the patient's perspective, face validity was satisfactory for both dialysis samples. Psychometric analyses of the UP-Dial for each dialysis sample had good convergent validity. Spearman rho correlations indicate a positively strong correlation (0.73 to 0.74) with global itching, a positively moderate correlation (0.33 to 0.58) with DLQI, PSQI, global fatigue, SSS-8, and PHQ-9, and a negatively moderate correlation (-0.39 to -0.58) with EQ-5D-5L and KDQOL-36. The discriminant validity was satisfactory with a group of moderate and severe burden of pruritus for both dialysis samples. For scale reliability, the UP-Dial revealed excellent internal consistency (Cronbach's α = 0.89 and McDonald's ω = 0.90) and reproducibility (intraclass correlation 0.84 to 0.85) for both dialysis samples. Regarding psychometric properties, no statistically significant differences between dialysis samples were observed (all P > 0.05). CONCLUSIONS: The findings reaffirm good measurement properties of the UP-Dial 14-items in hemodialysis and peritoneal dialysis patients with chronic pruritus. These suggest a transferability of the UP-Dial as a PRO measure in clinical trial and practice settings.