Development of a multivariable prediction model for plantar foot ulcer recurrence in high-risk people with diabetes

Abstract

Correspondence to Dr Sicco A Bus; s. a. bus@ amsterdamumc. nl To cite: aan de Stegge WB, Abu-Hanna A, Bus SA. Development of a multivariable prediction model for plantar foot ulcer recurrence in high-risk people with diabetes. Original research © Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY. Published by BMJ. Significance of this study What is already known about this subject? ► Several etiological risk factors models exist to identify variables that are associated with ulcer recurrence in high-risk people with diabetes; most risk factors are non-modifiable. ► However, most studies use inconsistent terminology to describe these models and to interpret them and are not validated. ► A validated prediction model allows more accurate assessment of ulcer recurrence risk and provides valuable information for patient follow-up and treatment. What are the new findings? ► The presence of a minor lesion, living alone, increased barefoot peak plantar pressure, longer duration of having a previous foot ulcer and less variation in daily stride count are predictors of plantar foot ulcer recurrence in high-risk people with diabetes. ► Predictors of plantar foot ulcer recurrence attributed to unrecognized repetitive stress as primary biome-chanical mechanism are presence of a minor lesion, longer duration of having a previous foot ulcer and location of the previous foot ulcer. ► Most predictors are variables that can be easily obtained by healthcare professionals and some predic-tors are modifiable factors that can be targeted for intervention. How might these results change the focus of research or clinical practice? ► These prediction models allow the clinician and practitioner to timely identify patients who are at risk of developing a recurrent plantar foot ulcer and to communicate this risk with the patient. ► Additionally, they can be used to select suitable patients for therapy and guide clinician and patient in joint decision-making for preventative treatment. AbStrAct Introduction Forty per cent of people with diabetes who heal from a foot ulcer recur within 1 year. The aim was to develop a prediction model for plantar foot ulcer recurrence and to validate its predictive performance. Research design and methods Data were retrieved from a prospective analysis of 171 high-risk patients with 18 months follow-up. Demographic, disease-related, biomechanical and behavioral factors were included as potential predictors. Two logistic regression models were created. Model 1 for all recurrent plantar foot ulcers (71 cases) and model 2 for those ulcers indicated to be the result of unrecognized repetitive stress (41 cases). Tenfold cross-validation, each including five multiple imputation sets, was used to internally validate the prediction strategy; model performance was assessed in terms of discrimination and calibration. Results The presence of a minor lesion, living alone, increased barefoot peak plantar pressure, longer duration of having a previous foot ulcer and less variation in daily stride count were predictors of the first model. The area under the receiver operating curve was 0.68 (IQR 0.61-0.80) and the Brier score was 0.24 (IQR 0.20-0.28). The predictors of the second model were presence of a minor lesion, longer duration of having a previous foot ulcer and location of the previous foot ulcer. The area under the receiver operating curve was 0.76 (IQR 0.66-0.87) and the Brier score was 0.17 (IQR 0.15-0.18). Conclusions These validated prediction models help identify those patients that are at increased risk of plantar foot ulcer recurrence and for that reason should be monitored more carefully and treated more intensively.