September 2011

Study Cites Eleven Risk Factors That Could Predict Amputation

By Brian McCurdy, Senior Editor

Given that lower extremity amputation is a devastating consequence of diabetic foot infection, physicians must be vigilant for the signs that could presage amputation. In a new study in Diabetes Care, authors have developed a risk score of 11 factors that could predict amputation.

   Researchers identified 3,018 patients who were hospitalized for culture-documented diabetic foot infection at 97 hospitals in the U.S. between 2003 and 2007. Among those patients, 21.4 percent underwent a lower extremity amputation.

   The 11 risk factors for amputation, in ascending order of point value, are: chronic renal disease or creatinine >3 mg/dL; male sex; temperature 100.5°F; age 50 or older; ulcer with cellulitis; history of amputation; albumin 11,000 per mm3); surgical site infection; and transfer from another acute care facility.

   Authors note that treatment of a patient with a low score may require fewer medical resources than a patient with a high risk score. The study also says in an attempt to avoid amputation, healthcare providers should concentrate efforts on a patient with a risk score of more than 21 as they have a 50 percent chance of amputation.

   Lead study author Benjamin A. Lipsky, MD, notes researchers developed the risk score specifically to use information that is present at (or soon after) the time of hospitalization. As he notes, this info includes findings from the history, physical examination or simple laboratory tests. He foresees “relatively minimal” organizational challenges for healthcare facilities implementing this scoring system. Dr. Lipsky says facilities would just need to educate providers about the score and perhaps provide a score sheet with explanations on how to use it.

   Although the study used a database of patients who were hospitalized for their diabetic foot infection, this risk score would likely apply to the majority of patients who do not require hospitalization, according to Dr. Lipsky, a Professor of Medicine at the University of Washington and the Director of the Primary Care Clinic at the VA Puget Sound Health Care System. He and his co-authors would like to see the score validated in such a population.

   David G. Armstrong, DPM, MD, PhD, cites the importance of the risk score system, saying it will be helpful to have a predictable system as another tool to predict outcomes. He compares this to a wound classification system, which is “highly predictive of good and bad outcomes” when a patient presents with a wound.

   Dr. Armstrong has found the most critical predictors of amputation to be infection, ischemia and renal disease. He expresses surprise that renal disease was not more of a factor in the study.

   “We believe that people on dialysis, people with end-stage renal disease and people with kidney disease are going to become increasingly important targets for aggressive intervention or hospice,” says Dr. Armstrong, the Director of the Southern Arizona Limb Salvage Alliance (SALSA).

   Dr. Lipsky would like to see if the score can be further simplified and refined so clinicians can remember it more easily. He would also like to see the risk score applied to patients in other countries and healthcare systems.

How Effective Is Endovascular Intervention For Patients With DFUs And PAD?

By Brian McCurdy, Senior Editor

A recent study in International Angiology asserts that for patients with diabetic foot ulcers (DFU) and peripheral arterial disease (PAD), endovascular intervention may not make much of a difference in major amputation or survival rates.

   The authors conducted a retrospective two-year review of 135 limbs in 115 patients with diabetic foot ulcers and PAD. During a median follow-up of 17 months, 44 percent of the ulcers did not heal, 15 percent of the patients had a major amputation and 42 percent of patients died. The authors looked at three groups: those who had attempted endovascular leg revascularization (75 patients); those who had conservative care (42 patients); and those who were deemed unreconstructable (18 patients). The study authors found no significant difference among the groups in terms of wound healing, major amputation or death.

   Khurram Khan, DPM, has found that most of his patients with DFUs and PAD do well in the short term, six months or less, with endovascular intervention. However, in the long term, he says diabetes and the disease process cause a higher recurrence of the occlusion.

   Of interest is that in the International Angiology study, most of the patients selected for endovascular procedure had proximal disease. However, performing an endovascular procedure proximally in patients with distal disease will not correct the problem and result in lower healing rates, according to Dr. Khan, an Assistant Professor in the Division of Medical Sciences at the New York College of Podiatric Medicine.

   Jonathan Key, DPM, also notes that his experience with endovascular intervention does not correlate with that of the study authors. He has found that choosing salvageable limbs and vascular lesions that will benefit from an endovascular procedure will often make a difference.

   “Seamless communication between the vascular surgeon and podiatric surgeon is also a vital component in the success of these cases,” says Dr. Key, a Clinical Instructor in the Department of Orthopaedics and Rehabilitation at Yale University School of Medicine in New Haven, Conn.

   Dr. Khan notes patients who have had diabetes for less than 10 years, have good glucose control and an appreciation of the disease and the process do much better with endovascular intervention than those with longstanding disease and comorbidities such as end-stage renal disease and coronary artery disease.

Study Looks At Adjunctive Immunokine For DFUs

By Danielle Chicano

A recent study published online with the Journal of Foot and Ankle Surgery suggests that combining WF10 (immunokine) with standard therapy may be beneficial in the treatment of diabetic foot ulcers (DFUs).

   The study, conducted in Thailand, compared results from 20 patients being treated with the combination of immunokine and standard therapy to the results of 20 patients who received standard therapy and placebo. Over a nine-week period, researchers assessed patients, ranging in age between 12 and 80, with the wound severity score (WSS) and monitored results weekly. Upon completion of the study, the immunokine group demonstrated a significant decrease in the WSS in comparison to the placebo group.

   Subgroup analyses also revealed statistically significant decreases in inflammation, infection and necrotic tissue in the adjunctive immunokine group. However, Gerit Mulder, DPM, MS, cautions against relying too heavily on the subgroup analysis findings, given the small size of the study population.

   “Subgroup analysis in an already small study population may have no statistical significance,” explains Dr. Mulder, the Director of the Wound Treatment and Research Center at the University of California-San Diego. “The decrease in the three factors mentioned (inflammation, infection and necrotic tissue) needs to be looked at in the entire population of 40 patients and not in subsets.”

   The authors note a few potential study limitations, one of which is the inclusion of patients with a higher WSS, that of 8 or greater, in a potentially salvageable foot. Dr. Mulder also raises the question of how necrotic tissue would increase in a DFU unless there were repetitive trauma, which was not addressed.

   Dr. Mulder also notes that the researchers should clearly specify the degree of infection and inflammation to differentiate the infection from heavy colonization and non-infection levels of bacterial burden. Dr. Mulder notes this could also help determine if the inflammation present is detrimental to wound closure.

   “I do believe (this study) may trigger further research (of immunokine) as a treatment modality. However, the study design would have to be changed so that complete closure is the endpoint,” says Dr. Mulder.

   The study authors note that immunokine is administered intravenously and is primarily used for chronic inflammatory disorders. Dr. Mulder adds that there are new biologic and drug-related studies that are also looking at inflammation and infection.

   “There are Phase II trials being initiated on drugs that decrease the inflammatory response and cell mediated death,” explains Dr. Mulder. “However, this may be of greater significance in the inflammatory ulcer (vasculitic) than the diabetic neuropathic ulcer.”

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