Impact of case‐mix adjustment on observed variation in the healing of diabetic foot ulcers at 12 weeks using data from the National Diabetes Foot Care Audit of England and Wales: A cohort study

Aim This cohort study investigates the extent to which variation in ulcer healing between services can be explained by demographic and clinical characteristics. Methods The National Diabetes Foot Care Audit collated data on people with diabetic foot ulcers presenting to specialist services in England and Wales between July 2014 and March 2018. Logistic regression models were created to describe associations between risk factors and a person being alive and ulcer‐free 12 weeks from presentation, and to investigate whether variation between 120 participating services persisted after risk factor adjustment. Results Of 27,030 people with valid outcome data, 12,925 (47.8%) were alive and ulcer‐free at 12 weeks, 13,745 (50.9%) had an unhealed ulcer and 360 had died (1.3%). Factors associated with worse outcome were male sex, more severe ulcers, history of cardiac or renal disease and a longer time between first presentation to a non‐specialist healthcare professional and first expert assessment. After adjustment for these factors, four services (3.3%) were more than 3SD above and seven services (5.8%) were more than 3SD below the national mean for proportions that were alive and ulcer‐free at follow‐up. Conclusions/Interpretations Variation in the healing of diabetic foot ulcers between specialist services in England and Wales persisted after adjusting for demographic characteristics, ulcer severity, smoking, body mass index and co‐morbidities. We conclude that other factors contribute to variation in healing of diabetic foot ulcers and include the time to specialist assessment.