Determining the Minimal Important Difference for the Wound-QoL Questionnaire

Janine Topp,1 Christine Blome,1 Matthias Augustin,1 Nicole Mohr,1 Eike Sebastian Debus,2 Holger Diener,2 Rachel Sommer1 1Institute for Health Services Research in Dermatology and Nursing (IVDP), German Center for Health Services Research in Dermatology (CVderm), University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany; 2Department of Vascular Medicine, University Medical Center Hamburg‐Eppendorf (UKE), Hamburg, GermanyCorrespondence: Rachel SommerInstitute for Health Services Research in Dermatology and Nursing (IVDP), German Center for Health Services Research in Dermatology (CVderm), University Medical Center Hamburg-Eppendorf (UKE), Hamburg, GermanyTel +49 (0) 40 7410 24724Fax +49 (0) 40 7410 40160Email r.sommer@uke.deBackground: The questionnaire for the quality of life with chronic wounds (Wound-QoL) is a valid and reliable instrument to determine the disease-specific health-related QoL of patients with chronic wounds. For the interpretation of HRQoL scores, it is additionally important to know which differences in scores are considered meaningful. The minimal important difference (MID) is defined as a change in HRQoL that a patient would consider meaningful, such that the patient would judge a treatment to be beneficial and worthy of repeating.Objective: To interpret changes in the Wound-QoL scores and draw conclusions regarding the relevance of detected changes; the purpose of this study was to estimate the MID of the Wound-QoL global score and its subscales for patients with chronic wounds.Patients and Methods: Patients completed the Wound-QoL before and four to six weeks after treatment and additionally gave a global rating of wound status change after treatment. The global rating of change served as an anchor question. MIDs were calculated based on an anchor-based and a distribution-based method.Results: In total, 227 patients participated in the study. The mean age of the study population was 66.9 (± 12.7) median was 69.5, and 51.5% of the patients were female. MIDs for the Wound-QoL global score ranged from 0.47 to 0.52, proposing an overall estimation of 0.50.Conclusion: The results can be used to measure and interpret changes in wound-specific QoL over time.Keywords: MID, minimal important difference, health-related quality of life, chronic wounds