Members of the International Working Group on the Diabetic Foot (IWGDF) presented up-to-date guidelines for the diagnosis, prognosis and treatment of diabetic foot ulcers at the 29th conference of the European Wound Management Association (EWMA; 5–7 June, Gothenburg, Sweden), highlighting development on the areas of infection and peripheral arterial disease (PAD).
First revealed at the 8th International Symposium on the Diabetic Foot (22–25 June 2019, The Hague, The Netherlands), the eight new documents also include guidelines for offloading, the prevention of wounds, wound classification and wound healing.
The process of making the guidelines, according to Benjamin A. Lipsky (University of Washington, Seattle, USA), involved the formulation, by a multidisciplinary working group of experts-in-the field, of clinical questions and key outcome measures “that clinicians would care about” when treating patients with diabetic foot problems. These questions were reviewed by clinicians from all over the world and a systematic review of the complete scientific literature was subsequently performed. Once this had been achieved, recommendations were graded to establish how useful they might be.
Diagnosis and treatment of foot infections
It is estimated that at least 25% of all persons with diabetes will eventually develop a foot infection, and this problem remains the most common cause of both diabetes-related hospitalisations and lower extremity amputations. As non-specialists are usually responsible for treating these infections, a new guideline was considered necessary by the IWGDF, expanding what was published in 2016 on the diagnosis and management of foot infections in persons with diabetes.
In addition to this, the updated recommendations aim to combat a “global antimicrobial crisis”. Lipsky said: “We are not producing new antibiotics and the ones we have are not as useful because of the developing resistance of microorganisms, so we have to use the antibiotics we have available in the wisest possible way.”
In support of the guideline, the infection committee of the IWGDF produced an update of a 2015 systematic review of interventions for treating infection, and a first time systematic review on the diagnosis of infection. The guideline updates the severity of infection classification scheme (see below) that the infection committee developed in 2004, with osteomyelitis—an infection of the bone—now having the separate designation of “O”.
Key recommendations on diagnosis, as explained by Lipsky, encourage physicians to assess all diabetic foot ulcers according to the IWGDF classification system, which grades diabetic foot patients from 1–4 depending on whether they have no infection, a mild infection, a moderate infection or a severe infection. In cases of serious infection, a patient should be hospitalised, while outpatient treatment would be suitable for most moderate and mild cases.
The performance characteristics of a number of helpful diagnostic tests are detailed in the guidelines, such as a probe-to-bone test, various serum inflammatory markers and imaging techniques. Lipsky added that if there is an infected wound “you should culture tissue, not send swab specimens,” and process them using standard methods as opposed to newer molecular techniques. In selected cases, potentially infected bone should be sampled for a definitive diagnosis of osteomyelitis or to establish the causative pathogen(s) and antibiotic susceptibility results.
Turning his focus to guidelines for treating infection, Lipsky emphasised that antibiotics shown to be effective in clinical trials should be selected based on the likely pathogen(s), severity of infection and risk of adverse events, and be administered orally in mild and most moderate cases. Regarding the duration of therapy, he stated: “Most of us treat much too long. There is good evidence based on randomised controlled trials that no more than one to two weeks of treatment is necessary for the vast majority of soft tissue infections, and no more than six weeks for bone infections.”
Treating patients with PAD
Presented by Nicolaas Schaper (Maastricht, The Netherlands), the new guideline on the management of PAD in patients with a foot ulcer and diabetes aims to tackle its association with a poor prognosis and support non-vascular specialists with diagnosis and treatment, especially as there is currently “weak evidence” to underpin clinical practice.
Looking at those affected by PAD, Schaper underlined that in developed countries 30-40% of persons with diabetes, including younger people, have PAD. These patients face a much higher risk of amputation as the PAD frequently progresses faster and is associated with more severe disease, compared to persons without diabetes. Schaper explained this situation using the results of a study: “If a patient has claudication, one in 20 of those with diabetes underwent amputation. If a patient does not have diabetes, the amputation rate is one in a 100, so it is a huge increased risk.” Once a diabetic foot ulcer has developed, up to 50% of the patients have signs of PAD.
The first part of the guideline centres around the diagnosis of PAD, asserting that the disease should be excluded in diabetic foot patients as soon as possible. This cannot be achieved with a clinical examination alone, as even those with severe PAD can demonstrate a good pulse in the foot; instead, more advanced examinations to test ankle and toe pressure are required. While there is no single modality in place, PAD is considered unlikely if triphasic pedal Doppler waveforms are measured, the ankle-brachial index is between 0.9 and 1.3, and the toe-brachial index is 0.75 or higher.
Once PAD has been diagnosed, the physician must assess the probability of healing when estimating the need for revascularisation. Using the WIfI classification system, which considers other key aspects such as the wound, ischaemia and foot infection, it is possible to estimate the amputation risk and determine whether revascularisation would be beneficial.
Although this system is a useful guide, there is still a great amount of uncertainty and physicians must be prepared to change strategy. Schaper said: “We advise that if a patient has PAD and does not heal within 4–6 weeks, then go to imaging and revascularise. If all your initial tests are normal and you treat the patient optimally, there is still a chance that the patient has PAD, because all the tests are to a certain extent unreliable.” For diabetic foot patients with both PAD and infection, Schaper further emphasised the need to treat immediately, as once there is an infection as well as PAD, the risk of amputation rises greatly. “Time is tissue in these patients,” he said.
Following the completion of these two stages (diagnosing and estimation of prognosis), any approach to treatment should involve a multi-disciplinary team of vascular specialists and aim to direct blood flow to one or more arteries, preferably in the anatomical region of the ulcer. The revascularisation technique should also be selected based on the individual factors of each patient and local factors.
In their closing remarks, both speakers considered the key controversies and conclusions raised by their respective guidelines. For patients with PAD, Schaper affirmed that revascularisation decisions are complex due to the potential for spontaneous healing, and called upon physicians to optimise other aspects of care, as described in practical guidelines of the IWGDF.
Lipsky also raised a number of important questions about what the best approach to imaging bone and soft tissue infections might be, as well as the potential viability and usefulness of topical or local antimicrobial therapies, which are among the topics that will be explored further with the foundation of a new guideline established.