Prognostic models for predicting the risk of foot ulcer or amputation in people with type 2 diabetes: a systematic review and external validation study

Joline W J Beulens,Giel Nijpels,Josan S Yauw,Petra J M Elders,Ron Herings,Amber A Van Der Heijden,Karel G M Moons,Roderick C Slieker,Talitha Feenstra

doi:10.1007/s00125-021-05448-w

Abstract

Aims/hypothesisApproximately 25% of people with type 2 diabetes experience a foot ulcer and their risk of amputation is 10–20 times higher than that of people without type 2 diabetes. Prognostic models can aid in targeted monitoring but an overview of their performance is lacking. This study aimed to systematically review prognostic models for the risk of foot ulcer or amputation and quantify their predictive performance in an independent cohort.MethodsA systematic review identified studies developing prognostic models for foot ulcer or amputation over minimal 1 year follow-up applicable to people with type 2 diabetes. After data extraction and risk of bias assessment (both in duplicate), selected models were externally validated in a prospective cohort with a 5 year follow-up in terms of discrimination (C statistics) and calibration (calibration plots).ResultsWe identified 21 studies with 34 models predicting polyneuropathy, foot ulcer or amputation. Eleven models were validated in 7624 participants, of whom 485 developed an ulcer and 70 underwent amputation. The models for foot ulcer showed C statistics (95% CI) ranging from 0.54 (0.54, 0.54) to 0.81 (0.75, 0.86) and models for amputation showed C statistics (95% CI) ranging from 0.63 (0.55, 0.71) to 0.86 (0.78, 0.94). Most models underestimated the ulcer or amputation risk in the highest risk quintiles. Three models performed well to predict a combined endpoint of amputation and foot ulcer (C statistics >0.75).Conclusions/interpretationThirty-four prognostic models for the risk of foot ulcer or amputation were identified. Although the performance of the models varied considerably, three models performed well to predict foot ulcer or amputation and may be applicable to clinical practice.Graphical abstract

Highlights

Worldwide, there was an estimated 463 million people living with diabetes in 2019
Studies were included if the following criteria were met: (1) the prognostic model was developed for people with type 2 diabetes or included type 2 diabetes as a predictor; (2) the minimal follow-up period was 1 year; and (3) the outcome was foot ulcer, amputation, neuropathy, or a combination of these
Characteristics of the models We identified 21 studies that presented 34 prognostic models to predict the risk of foot ulcer or amputation (Table 1)

Summary

Introduction

By 2045 its prevalence is expected to increase to 700 million [1], with 90% being type 2 diabetes. People with type 2 diabetes are monitored annually to assess their risk of foot ulcer and amputation [5]. To guide monitoring frequency or initiate appropriate treatment, the risk of foot ulcer or amputation can be estimated using prognostic models. Such models might be useful in times when prioritisation of routine care is needed, as is the case during the current coronavirus disease 2019 (COVID-19) pandemic. The impact of the use of the prognostic model in clinical practice on decision making or health outcomes should be tested

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