Risk assessments and structured care interventions for prevention of foot ulceration in diabetes: development and validation of a prognostic model.

BACKGROUND

Diabetes-related foot ulcers give rise to considerable morbidity, generate a high monetary cost for health and social care services and precede the majority of diabetes-related lower extremity amputations. There are many clinical prediction rules in existence to assess risk of foot ulceration but few have been subject to validation.

OBJECTIVES

Our objectives were to produce an evidence-based clinical pathway for risk assessment and management of the foot in people with diabetes mellitus to estimate cost-effective monitoring intervals and to perform cost-effectiveness analyses and a value-of-information analysis.

DESIGN

We developed and validated a prognostic model using predictive modelling, calibration and discrimination techniques. An overview of systematic reviews already completed was followed by a review of randomised controlled trials of interventions to prevent foot ulceration in diabetes mellitus. A review of the health economic literature was followed by the construction of an economic model, an analysis of the transitional probability of moving from one foot risk state to another, an assessment of cost-effectiveness and a value-of-information analysis.

INTERVENTIONS

The effects of simple and complex interventions and different monitoring intervals for the clinical prediction rules were evaluated.

MAIN OUTCOME MEASURE

The main outcome was the incidence of foot ulceration. We compared the new clinical prediction rules in conjunction with the most effective preventative interventions at different monitoring intervals with a 'treat-all' strategy.

DATA SOURCES

Data from an electronic health record for 26,154 people with diabetes mellitus in one Scottish health board were used to estimate the monitoring interval. The Prediction Of Diabetic foot UlcerationS (PODUS) data set was used to develop and validate the clinical prediction rule.

REVIEW METHODS

We searched for eligible randomised controlled trials of interventions using search strategies created for Ovid

RESULTS

The clinical prediction rule was found to accurately assess the risk of foot ulceration. Digital infrared thermometry, complex interventions and therapeutic footwear with offloading devices were found to be effective in preventing foot ulcers. The risk of developing a foot ulcer did not change over time for most people. We found that interventions to prevent foot ulceration may be cost-effective but there is uncertainty about this. Digital infrared thermometry and therapeutic footwear with offloading devices may be cost-effective when used to treat all people with diabetes mellitus regardless of their ulcer risk.

LIMITATIONS

The threats to the validity of the results in some randomised controlled trials in the review and the large number of missing data in the electronic health record mean that there is uncertainty in our estimates.

CONCLUSIONS

There is evidence that interventions to prevent foot ulceration are effective but it is not clear who would benefit most from receiving the interventions. The ulceration risk does not change over an 8-year period for most people with diabetes mellitus. A change in the monitoring interval from annually to every 2 years for those at low risk would be acceptable.

FUTURE WORK RECOMMENDATIONS

Improving the completeness of electronic health records and sharing data would help improve our knowledge about the most clinically effective and cost-effective approaches to prevent foot ulceration in diabetes mellitus.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016052324.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in

People with diabetes sometimes have problems with their feet that can become serious and make getting around harder and life less enjoyable. We have developed a test based on a simple score to find out a person’s risk of getting a foot ulcer. We also wanted to know how often the test needs to be done. People who have been tested and learn that they might go on to have foot problems rightly expect to be given treatment that stops the problem happening in the first place. In this project, we read many written reports about the best treatments to prevent foot ulcers. We found that some things can prevent foot ulcers, such as wearing special shoes and insoles, taking the temperature of the skin of the foot and resting when the temperature rises, and receiving specialist care from diabetes foot care teams. However, we also looked at the costs of the test and treatments and found that some treatments are better value for money than others. By using people’s health data from NHS computers, we discovered that very few people with diabetes develop a worse risk score for foot ulcers as time goes on, and it seems that being tested every year is not necessary for everyone. New clinical trials might help to improve foot health for people with diabetes, but if all of the researchers who have collected data from people in clinical trials shared their data it would be possible to find out more about who will gain most from these treatments without spending a lot on new research. It is clear that better input of patients’ health data into NHS computers will benefit diabetes research in the future.