A number of studies have reported the rates and predictors for healing patients who present with a diabetic foot ulcer; combinations of infected and uninfected ulcers. Recently we summarised an Australian study that reported for the first time the rates and predictors of developing an infection in patients who present with an uninfected diabetic foot ulcer. But what about patients who present with an infected diabetic foot ulcer, what are the predictors for healing after that? Well just like in the Ashes cricket, the English have tried to go one up on us and have investigated just that.
A new study – published in the UK diabetes journal Diabetic Medicine – followed 300 patients who presented with an infected diabetic foot ulcer to one of 25 English diabetic foot clinics for 12 months. For those keeping a good eye on our summaries, you will note this study is a follow-up study to one we reported earlier comparing the culture results from swabs and deep tissue specimens. In the earlier study the authors recruited 400 patients with a diabetic foot ulcer that was clinically infected based on the Infectious Diseases of America classification system. They also recorded their demographics, PEDIS diabetic foot ulcer score, and treatment along with culture results and any antimicrobial management.
In this new follow up study the authors performed a chart audit of all the original patients that consented (n=299) to see what happened to those patients over the next 12-months with regard “ulcer-related events”, including healing, recurrence, revascularization, amputation and death.
First, they found 44.5% had healed at 12-months; with a median time to healing of 4.5 months. Second, they found: 17% underwent an amputation at a median time to amputation of 2 months; 6% underwent revascularization at a median time of 3 months; and 15% died at a median time of 6 months. Third, in those that healed, 10% had their ulcer recur at a median time of 2 months post-healing. Fourth, the predictors of poor healing (after controlling for all other factors) were having peripheral arterial disease (ABI <0.9 or TBI <0.6), >2 month ulcer duration at presentation and multiple ulcers.
When they compared their infected diabetic foot ulcer findings to other studies investigating diabetic foot ulcers (combinations of infected and uninfected) they found overall they had worse outcomes. The healing rate at 12-months of infected diabetic foot ulcers was worse than combined diabetic foot ulcers (i.e. 45% v ~70%), amputations were similar (i.e. 17% v ~20%), but death was worse (i.e. 15% v ~6%).
As for any study this study had strengths and limitations. The strengths included: investigating a large number of patients with clinically infected diabetic foot ulcers, collecting validated ulcer characteristics and cultures, following them for 12 months and adjusting for multiple factors. The limitations included: having 25% of the original patients lost to follow up, although they had similar characteristics to those they followed; they used chart audits which always has some unreliability; and the authors did not have data for if and when the infection resolved which would have shone much more light on ulcer healing.
In conclusion the authors stated, “people with a clinically infected diabetic foot ulcer have a poor prognosis. Our results also confirmed that the presence of limb ischaemia, multiple foot ulcers and a longer ulcer duration were most predictive of poor 12-month outcomes.”
This very nice study should inform larger studies that prospectively examine the characteristics and care of patients presenting with infected diabetic foot infections. In particular future studies should explore the effect of different antibiotics and antimicrobials on infection resolution and ulcer healing. We at DFA are aware that such a study just may be about to happen right here in Australia; so perhaps we can get one back on those English, just like in the Ashes ;).