Predictors of diabetic foot amputation identified
medwireNews: Arterial disease and neuropathy, along with poor vision and reduced kidney function, are associated with a significantly increased risk for lower limb amputation in men with diabetes, US researchers report.
They hope that “better knowledge of these limb- and person-level factors will result in continuing improvement in limb preservation among patients with diabetes through the development of remediation strategies.”
In a prospective study with 22 years of follow-up, Edward Boyko (Seattle Epidemiologic Research and Information Center, Washington) and colleagues identified 136 lower limb amputations (65% above the ankle) among 1461 men (mean age 62.4 years at baseline) with diabetes who did not have foot ulcers at baseline. This gave an incidence of 5.3 amputations per 1000 limb–years.
In unadjusted analyses, baseline measurements of age, prior foot ulcer or amputation, insulin use, poor vision, glycated hemoglobin level, estimated glomerular filtration rate (eGFR), serum albumin, systolic blood pressure, sensory neuropathy as measured by 10 g monofilament, Charcot deformity, and ankle-brachial index (ABI) were significantly associated with amputation risk.
However, in adjusted models that included time-varying measurements, a number of these person- and limb-level associations lost significance.
Among those remaining statistically significant both low ABI (≤0.5) and high ABI (≥1.3) predicted a significantly increased risk for amputations, compared with a medium-level measurement (>0.9 to <1.3), at hazard ratios (HRs) of 3.98 and 2.20, respectively.
Sensory neuropathy also predicted a significantly higher amputation risk, with a HR of 3.09.
Poor visual acuity (HR=1.70) and low eGFR (HR=1.18 per standard deviation increase) were the only person-level factors associated with increased amputation risk on multivariate analysis.
Writing in Diabetes Care, Boyko et al comment that impaired vision could be a marker for disease burden but could “also impair foot self-care and lead to diminished ability to identify and treat lower-extremity lesions that might set the stage for amputation,” while renal impairment may be “causally related to the development of amputation in addition to serving as a marker for disease burden.”
By contrast, age above 70 years (HR=0.13) and increased weight (HR=0.78 per 21.4 kg increase) were associated with a reduction in amputation risk.
The researchers describe these findings as “counterintuitive” and say the reasons for the reduced risks are currently unclear.
Boyko and team conclude that their study “has identified several potentially preventable or correctable factors that may lead to strategies to reduce the risk of this diabetes-related complication.”
Indeed, intensive glycemic control has been shown to reduce sensory neuropathy and abnormally high ABI, while low ABI due to occlusive atherosclerosis could be avoided by controlling atherosclerosis risk factors, they note.
In addition, the authors say that “[t]he potential for correction of vision in preventing amputation is an area deserving further investigation.”
By Laura Cowen
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