Developing a foot ulcer risk model: what is needed to do this in a real‐world primary care setting?. Issue 11 (13th December 2018) - Heald, A.
Abstract: Aim: To determine how routinely collected data can inform a risk model to predict de novo foot ulcer presentation in the primary care setting. Methods: Data were available on 15 727 individuals without foot ulcers and 1125 individuals with new foot ulcers over a 12‐year follow‐up in UK primary care. We examined known risk factors and added putative risk factors in our logistic model. Results: People with foot ulcers were 4.2 years older (95% CI 3.1–5.2) than those without, and had higher HbA1c % (mean 7.9 ± 1.9 vs 7.5 ± 1.7) / HbA1c mmol/mol (63 ± 21 vs 59 ± 19) (p<0.0001) concentration [+0.45 (95% CI 0.33–0.56), creatinine level [+6.9 μmol/L (95% CI 4.1–9.8)] and Townsend score [+0.055 (95% CI 0.033–0.077)]. Absence of monofilament sensation was more common in people with foot ulcers (28% vs 21%; P <0.0001), as was absence of foot pulses (6.4% vs 4.8%; P =0.017). There was no difference between people with or without foot ulcers in smoking status, gender, history of stroke or foot deformity, although foot deformity was extremely rare (0.4% in people with foot ulcers, 0.6% in people without foot ulcers). Combining risk factors in a single logistic regression model gave modest predictive power, with an area under the receiver‐operating characteristic curve of 0.65 (95% CI 0.62–0.67). The prevalence of ulceration in the bottom decile of risk was 1.8% and in the top decile it was 13.4% (compared with an overall prevalence of 6.5%); thus, the presence of all six risk factors gave a relative risk of 7.4 for development of a foot ulcer over 12 years. Conclusion: We have made some progress towards defining a variable set that can be used to create a foot ulcer prediction model. More accurate determination of foot deformity/pedal circulation in primary care may improve the predictive value of such a future risk model, as will identification of additional risk variables. What's new?: Foot ulceration is the most common complication in diabetes, with a lifetime risk of 25%. The condition portends significant excess morbidity and mortality in individuals with diabetes already facing reduced life expectancy and unfavourable prognosis. Our aim was to determine how data collected in the course of diabetes reviews of patients in UK primary care can inform a risk model to predict de novo foot ulcer presentation. People with foot ulcers were significantly older than those without, and had higher HbA1c concentration, raised creatinine levels, and greater social disadvantage. Absence of monofilament sensation was more common in people with a foot ulcer, as was absence of foot pulses. More accurate determination of foot deformity and pedal circulation in the UK general practice setting may improve the predictive value of a future risk model for use in primary care.