Lower-extremity amputation score identifies high-risk diabetes patients
MedWire News: US researchers have developed a means to stratify risk for nontraumatic lower-extremity amputation (LEA) in hospital patients with a diabetic foot infection.
"This score may help clinicians identify patients at highest risk of LEA upon admission," explain Benjamin Lipsky (Veterans Administration Puget Sound Health Care System and the University of Washington, Seattle, Washington) and co-workers.
"Once patient identification is achieved, methods to reduce the risk can be investigated."
The team examined risk factors for LEA using information from 3018 patients at 97 US hospitals who were diagnosed with diabetic foot infection between 2003 and 2007, 21.4% of whom underwent LEA.
Data for 75% of patients was used to develop a score model, the remaining 25% of patients were used to validate the system.
Patients who required LEA were significantly older than those who did not (median age, 62 vs 60 years) and had a higher rate for in-hospital mortality (2.3% vs 1.1%).
Multivariate analysis identified 11 factors that were associated with risk for LEA. The researchers developed a scoring system using these predictors, with the greatest weight given to the strongest factors of surgical site infection, history of peripheral vascular disease, prior LEA, and a white blood cell count greater than 11,000 per mm3.
As reported in the journal Diabetes Care, this model had good discrimination and excellent calibration between predicted and observed LEA rates. Patients in the highest decile of score had a predicted probability of LEA of 58.7% versus 4.0% for those in the lowest decile; observed rates were 58.7% and 5.0%, respectively.
The score also had good calibration in the validation cohort, the researchers say.
The score was then simplified into a five risk strata - patients aged less than 50 years without other risk factors were calculated to have a 0% risk for LEA compared with a risk of around 50% for patients with a score of 21 points or more.
Lipsky et al suggest that their simplified score could help hospitals allocate resources. "In particular, a patient with a low score may need fewer medical resources than a patient with a high LEA risk score.
"At the other extreme, to try to avoid the tragedy of amputation, healthcare providers should concentrate efforts on a patient with a risk score of >21, who has a 50% chance of an LEA."
The researchers conclude: "We would like to see our risk score validated prospectively, including in patients treated on an outpatient basis."
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By Lynda Williams