The validity and reliability of the Thai-version of 5-D itch scale

Background: Pruritus is commonly associated with skin disorders. The 5-D itch scale was developed as a specific questionnaire for pruritus. Objective: This study aimed to evaluate the validity, reliability, and sensitivity to change of the Thai 5-D itch scale in Thai patients. Methods: The Thai Dermatology Life Quality Index (DLQI), patient’s global assessment of disease severity (PatGA-VAS), Chronic Urticaria Quality of Life Questionnaire (CU-Q₂ oL), and seven-day urticaria activity score (UAS7) were evaluated as correlation with Thai 5-D itch scale. Seventy-five stable patients (42 chronic urticaria patients and 33 eczema patients), who had no change in disease severity after 4-weeks were assessed for test-retest reliability. Results: Of 130 pruritus patients who were treated at Department of Dermatology, Siriraj Hospital, 65 patients were diagnosed with chronic urticaria. The others were diagnosed with eczema. The validity of Thai 5-D itch scale correlated strongly with Thai DLQI total score (r = 0.76, p < 0.0001) and PatGA-VAS (r = 0.79, p < 0.0001). The strong reliability of Thai 5-D itch scale was demonstrated as intraclass correlation coefficient of 0.90. The changes in Thai 5-D itch scale was correlated with the changes in PatGA-VAS and UAS7 which indicated that the Thai 5-D itch scale had good sensitivity to change (r = 0.66) and (r = 0.67), respectively. Conclusion: The Thai 5-D itch scale is a questionnaire with good validity, reliability and sensitivity to change to evaluate pruritus in Thai patients. This will support the use of 5-D itch scale in practice, in other languages.