Diabetic Foot Ulcers
A Prospective Study of Risk Factors for Diabetic Foot Ulcer


Funding agency

VA Rehabilitation Research and Development grant, supported in part by Veterans Affairs Merit Review Rehabilitation Research and Development


Description of work

Objective: To conduct a prospective study designed to identify risk factors for foot ulceration and lower extremity amputation associated with diabetes.


Research Plan

To date we have enrolled 789 diabetic subjects from the Puget Sound Health Care System’s Seattle General Internal Medicine outpatient clinic. We examine the subjects still enrolled annually for presence of possible risk factors for diabetic foot ulceration and for the occurrence of foot ulcer, lower extremity amputation and death.


Methodology

We enroll eligible subjects who meet the criteria for diabetes mellitus by physician diagnosis or treatment with a hypoglycemic medication or insulin. Subjects attend a Diabetic Foot Clinic where we assess the presence of suspected risk factors, grouped into four categories:

Circulation
Neuropathy
Foot Deformity
Self-Care Behaviors

We compare rates of outcome occurrence (incidence) by exposures of interest to determine which particular factors are related to risk of diabetic foot ulcer.


Findings

As of January 1996, we observed 110 (6.1 per 100 person years) foot ulcers occurring over a cumulative 1,812 person years. Using stepwise Cox regression analysis, the following factors were independently and significantly (< 0.05) related to foot ulcer risk: insensitivity to the 5.07 monofilament, relative risk (RR)=5.1, 95% confidence interval (Cl) 2.9-9.4; past history of foot or leg ulcer RR= 2.1, 95% Cl 1.2-3.4; marked hammer or claw toe deformity RR 1.7, 95% Cl 1.0-2.9; 30 mmHg reduction in dorsal foot TcPO2 RR 1.6, 95% Cl 1.0-2.4; reduced R-R change (by 5 beats) with breathing RR=1.9, 95% Cl 1.1-3.5; greater blood pressure drop by 30 mmHg RR=1.8, 95% Cl 1.1-2.8; and higher erythrocyte sedimentation rate (50 mm/hour increase) RR=1.7, 95% Cl 1.1-2.6. Subjects who develop a foot ulcer have an increased of death RR=2.55, 95% Cl 1.2-4.9 independent of self reported coronary heart disease and age. Multivariate logistic regression analysis of subjects with and without sensory neuropathy at study onset showed independent and significant (p <0.05) increases in risk of neuropathy associated with height, age, insulin use, duration of diabetes and ankle arm index <0.8. We examined the diagnostic utility of many common history and physical examination findings for the detection of peripheral vascular disease in 1,369 lower extremities from 687 diabetic subjects. We can obtain the probability of peripheral vascular disease from knowledge of the subject’s age, history of peripheral vascular disease, examination of the peripheral pulses by palpation and venous filling time. Other purported findings such as cold feet, have little diagnostic importance.

Clinical Relevance: It appears from current data that sensory and autonomic neuropathy and skin oxygenation will be important in the pathogenesis of diabetic foot ulcers. Final analysis, when completed in 1996, should provide additional interesting information concerning the risk factors for diabetic foot ulcer and potential means for prevention.


Faculty

Edward J. Boyko, M.D., M.P.H.: Principal Investigator
Jessie H. Ahroni, ARNP, MN, CDE: Project Manager
H.S.R.& D. FIELD PROGRAM

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Last reviewed: August 21, 1998 - Last updated: August 21, 1998 (em)