Study Cites Eleven Risk Factors That Could Predict Amputation

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 <96°F or >100.5°F; age 50 or older; ulcer with cellulitis; history of amputation; albumin <2.8 g/dL; history of peripheral vascular disease; white blood cell count >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.

By Brian McCurdy, Senior Editor