Transformation of 5-D itch scale and numerical rating scale in chronic hemodialysis patients

Background: Pruritus is a common and frustrating symptom in hemodialysis (HD) patients and 5-D itch scale is proposed as a reliable measurement of pruritus. However, information regarding 5-D itch scale categories is currently unavailable. We explored optimal cut-offs 5-D itching scale based on numerical rating scale (NRS) categories in HD patients. Methods: Four hundred and nine HD patients in China Medical University Hospital in December 2014 were included and severity of pruritus was estimated using NRS and 5-D itch scale. The association of NRS and 5-D itch scale was analyzed by linear regression. The optimal cut-offs for 5-D itch scale based on NRS categories were generated. Results: The average NRS was 3.4 +/- 3.0 and the average 5-D itch scale was 10.9 +/- 4.8. The 5-D score was strongly correlated with the NRS: r = 0.831 (p < 0.001). NRS = -2.31 + 0.52 x (5-D scale). The averages of 5-D scales were 6.4 +/- 1.5, 9.6 +/- 2.2, 13.1 +/- 3.2, 15.7 +/- 4.4, 19.5 +/- 4.4 for no, mild, moderate, severe, and very severe pruritus based on categorized NRS. A 5-D itch scale categories were proposed, <= 8 for NRS = 0, 911 for mild pruritus, 1217 for moderate pruritus, 1821 for severe pruritus and >= 22 for very severe pruritus. Conclusions: Categories for the 5-D itch scale were proposed based on the measurements of pruritus severity in HD patients. This information provides a simple solution that enables transformation between the 5-D itch scale and the numerical rating scale.