To gain accurate insight into the costs and cost-effectiveness of diabetic foot ulcer care, studies using decision analytic models are needed. We have discussed two studies modelling recently (here and here). A new study has been published, adding further weight to the discussion on costs and cost-effectiveness. As these modelling studies are relatively complex, and the outcomes dependent on many assumptions and choices, we will discuss these in this ‘latest research’ post.
This study was undertaken to identify scenarios in which two efforts could improve health outcomes at a lower costs in the long term: avoiding the development of diabetic foot ulcers (better prevention) and providing timely, adequate treatment for those with ulcers among patients at-risk (better treatment).
The analysis was based on a Markov model, where patients at risk of foot ulcers could experience six possible clinical events: no ulcer, uninfected ulcer, infected ulcer, limb loss, healed ulcer and death from any cause. A cohort of 100,000 hypothetical patients with diabetes but no current ulcer and no prior history of ulcer was simulated in the model for a period of 5 years. The cohort consisted of 3 risk groups. Low risk consisted of diabetic patients without peripheral neuropathy or peripheral arterial disease. Moderate risk was based on reported clinical outcomes of diabetic patients with peripheral neuropathy but without peripheral arterial disease. High risk was based on outcomes of diabetic patients with peripheral arterial disease, with or without peripheral neuropathy. The probabilities of moving between those clinical events were different for patients at low risk, moderate risk and high risk.
The Markov model compares two types of care, one with better prevention and one without. With better prevention, it was assumed that the incidence of initial ulcer occurrence would be reduced, while healing rates, infection rates and recurrence would be the same for two types of care. At the end of the modelling, total costs of the two types of care after 5 years were compared and it was determined whether the one with better prevention costs less. For any given set of effectiveness and cost of better intervention (e.g. relative risk of initial ulcer occurrence = 0.95 and cost of primary intervention is $25), the authors ran the model 1000 times. Each time, other variables such as healing rate took a random value from a distribution. They then calculated the number of times out of 1000 that the care with better intervention costs less.
One thing that distinguishes this study from other studies is that no assumption was made on the effectiveness of better prevention. Instead, levels of effectiveness were varied in the analysis. For example, the results showed that when the implementation of better prevention could reduce incidence of initial ulcer by 25% and the annual cost of better prevention per person was $125, then the better prevention had a 97% probability of being cost-saving (Table 4 in the article). However, if better prevention could only reduce the incidence by 10% for same annual cost, then the chance of being cost-saving would reduce to 9%. Only very low-cost ulcer prevention efforts that result in small decreases in ulcer incidence provide opportunities for cost-savings.
The study also investigated the impact of better treatment after the development of an initial or recurrent ulcer. Adequate treatment for ulcers in the low and moderate risk groups was assumed to consist of offloading and wound care provided within a month of ulcer occurrence. Adequate treatment for ulcers in the high risk group consisted of revascularization, offloading and wound care within a month of ulcer occurrence. Surprisingly, and contrary to the previous studies from Germany and Australia, they found this not to result in cost-savings. This seems to result from both a conservative estimate in the effect on wound healing improvement and amputation reduction following better treatment, as well as focussing on costs only. When cost-effectiveness was analysed, better treatment did result in more cost-effective outcomes.
One limitation of this study is that better prevention is not specified. The authors suggested in discussion that daily foot thermometry, podiatric care at regular intervals or direct education might achieve the long term cost-saving goals. They also stated that mobile phone-based reminders, self-identification of risk factors (ex. Ipswich touch test), and written brochures may be examples of such low-cost interventions that could be investigated for cost-savings potential. Another limitation is that, although the hypothetical cohort included low, moderate, and high risk patients, it was not known whether the risk might change over time and how this would influence the progression of clinical events. Probably the most important limitation is not analyzing the models for people with a history of foot ulceration, whereas prevention is most likely to be cost-effective in that population.
Overall, this study provided some evidence that better prevention directed at populations with diabetes without a current foot ulcer is likely to produce cost-savings when the prevention efforts have modest levels of cost and effectiveness, especially for those at moderate and high risk of ulceration. Better treatment, on the other hand, improves health outcomes, which is associated with higher overall costs in these models, but may improve cost-effectiveness by placing a monetary value on the improvements in quality of life of our patients.