Measurement of itching: validation of the Leuven Itch Scale

Abstract

Objective: To develop the Leuven Itch Scale (LIS), which measures itching through evaluation of the dimensions of the itch experience; and to provide evidence of the validity, reliability, and responsiveness of the LIS.

Materials and methods: A clinimetric study using a longitudinal design. Patients with burns (n=46), atopic dermatitis (n=63), or chronic urticaria (n=41) were included. Evidence for validity (based on test content, relations with other variables and internal structure), reliability and responsiveness of the LIS was evaluated.

Results: Validity evidence based on test content was demonstrated by very low percentages of invalid scores for most items. Validity evidence based on relations with other variables was found, because all hypotheses that were put forward could be accepted. With respect to validity evidence on internal structure, a significant moderate positive correlation was found between itch frequency and itch distress, and between itch frequency and severity. As hypothesized, itch severity and distress were strongly correlated. Test-retest reliability showed a moderate to almost perfect agreement for about half of the items. However, the remaining items could be subject to changes in the itch, rather than reflecting instability of the Leuven Itch Scale. In terms of responsiveness, the Leuven Itch Scale did not suffer from floor or ceiling effects and could detect changes in itch frequency in patients with burns.

Conclusion: The Leuven Itch Scale is a useful and clinimetrically sound instrument to measure pruritus in different patient populations affected by itching.