Diabetic Foot - Diagnosis

Diagnosis - updated: 15 March 2008

Diabetic Foot Ulcers: Prevention, Diagnosis and Classification

American Family Physician® > Vol. 57/No. 6 (March 15, 1998)

DAVID G. ARMSTRONG, D.P.M., and LAWRENCE A. LAVERY, D.P.M., M.P.H.,

Diabetic ulcers are the most common foot injuries leading to lower extremity amputation. Family physicians have a pivotal role in the prevention or early diagnosis of diabetic foot complications. Management of the diabetic foot requires a thorough knowledge of the major risk factors for amputation, frequent routine evaluation and meticulous preventive maintenance. The most common risk factors for ulcer formation include diabetic neuropathy, structural foot deformity and peripheral arterial occlusive disease. A careful physical examination, buttressed by monofilament testing for neuropathy and noninvasive testing for arterial insufficiency, can identify patients at risk for foot ulcers and appropriately classify patients who already have ulcers or other diabetic foot complications. Patient education regarding foot hygiene, nail care and proper footwear is crucial to reducing the risk of an injury that can lead to ulcer formation. Adherence to a systematic regimen of diagnosis and classification can improve communication between family physicians and diabetes subspecialists and facilitate appropriate treatment of complications. This team approach may ultimately lead to a reduction in lower extremity amputations related to diabetes.

FIGURE 1- Nylon monofilament test.

FIGURE 2. Usual locations of ulcers in the diabetic foot.

TABLE 2 Noninvasive Vascular Tests
Test	Abnormal value
Transcutaneous oxygen measurement Ankle-brachial index Absolute toe systolic pressure	Less than 40 mm Hg Less than 0.80: abnormal Less than 0.45: severe, limb-threatening Less than 45 mm Hg

Ankle brachial pressure index

From Wikipedia, the free encyclopedia

The Ankle Brachial Pressure Index (ABPI) is a measure of the fall in blood pressure in the arteries supplying the legs and as such is used to detect evidence of blockages (peripheral vascular disease). It is calculated by dividing the systolic blood pressure in the ankle by the higher of the two systolic blood pressures in the arms. The pressures in the posterior tibial artery and dorsalis pedis artery in the feet and the brachial artery at the elbow are estimated. A Doppler probe is used, through a device called the Pulse Volume Recorder (some variances may apply depending on the physician), to monitor the pulse while a sphygmomanometer (blood pressure cuff) is inflated above the artery. The cuff is deflated and the pressure at which the pulse returns is recorded. In a normal subject the pressure at the ankle pulses is slightly higher than at the elbow (there is reflection of the pulse pressure from the vascular bed of the feet, whereas at the elbow the artery continues on some distance to the wrist). The ABPI is the ratio of the ankle to arm pressure and an ABPI of greater than 0.9 is considered normal, suggesting that there is no significant peripheral vascular disease affecting the vessels of the legs. A reduced ABPI (less than 0.9) is consistent with peripheral artery occlusive disease (PAOD), with values below 0.8 indicating moderate diseased and below 0.5 severe disease. However, a value greater than 1.3 is considered abnormal, and suggests calcification of the walls of the arteries and noncompressible vessels, reflecting severe peripheral vascular disease. Studies in 2006 suggests that an abnormal ABPI may be an independent predictor of mortality, as it reflects the burden of atherosclerosis.

Pulsatility index is better than ankle-brachial doppler index for non-invasive detection of critical limb ischaemia in diabetes

Vasa. 2005 Nov;34(4):235-41

Janssen A.

BACKGROUND: Diabetic polyneuropathy of the feet and legs obscures the diagnosis of critical limb ischaemia (CLI) because of lack of pain sensation. Hence, the Fontaine classification does not apply to these patients. Furthermore, many of them will exhibit medial arterial calcification, which invalidates the application of sphygmomanometry. This study was done to evaluate the pulsatility index (P1) assessed at the ankle arteries by colour Doppler ultrasonography as a non-invasive method to diagnose CLI in diabetic polyneuropathy. PATIENTS AND METHODS: 140 legs of 106 diabetic patients were studied who presented with polyneuropathy and painlessness of the feet; of these, 117 feet displayed an ulcer or gangrene. CLI was defined as the need for arterial revascularisation, as indicated by the physicians in charge on the basis of a) a foot lesion Wagner grade 1-5, and b) a positive arteriography. All patients were subjected to 4 vascular assessment techniques: digital subtraction arteriography, ankle-brachial Doppler index, systolic ankle blood pressure, and PI. RESULTS: Of the 140 legs, 61 (44%) were affected by CLI, and 76 (54%) by medial arterial calcification. A PI < 1.2 indicated CLI with a sensitivity of 0.87 and a specificity of 0.62. The sensitivity and specificity of ankle-brachial index < 0.9, and of systolic ankle pressure < 70 mm Hg to predict CLI was 0.71 and 0.42, and 0.30 and 0.89, respectively. CONCLUSIONS: The pulsatility index is a better noninvasive technique than the ankle-brachial Doppler index or the systolic ankle pressure to assess critical limb ischaemia in diabetic polyneuropathy. A pulsatility index < 1.2 at the ankle arteries is a reliable criterion for diagnosis of CLI in diabetic patients with polyneuropathy.

Toe pressure measurements compared to ankle artery pressure measurements

Angiology. 2003 Jan;54(1):39-44

Kröger K, Stewen C, Santosa F, Rudofsky G.

The Trans-Atlantic Inter-Society Consensus (TASC)-recommended absolute toe pressure is < 30-50 mm Hg for definition of chronic critical limb ischemia (CLI). Toe pressures can be measured by different techniques. The authors analyzed the clinical use of the Doppler technique and an automatic device with optical sensors and estimated their value in documentation of chronic critical limb ischemia compared to ankle artery pressures. Three different investigations were performed: (1) In 16 healthy subjects the digital artery pressures were measured by using 3 different optical sensors (transmission, reflection, and microcirculation sensor) and compared to the systolic brachial pressure. (2) In 50 patients with and without peripheral arterial occlusive disease the toe pressures at digits 1 and 2 of both feet were determined by Doppler technique (8 MHz) and by optical sensors (cuff width constant 1.5 cm) and were compared to the ankle artery pressure determined by Doppler technique. (3) In 175 patients the toe pressures were measured at 1 toe and the ankle artery pressures were determined. In this group they estimated the clinical use of the toe pressure in regard to the definition of CLI (toe pressure < 50 mm Hg) compared to the ankle pressure < 70 mm Hg. The digital artery pressures measured with the different optical sensors, and the systolic brachial pressures were not significantly different and the correlation coefficients were around 0.7. In 21 of 50 patients the toe pressure at D1 and D2 could not be measured by Doppler technique because with the applied cuff no Doppler signal could be detected at the tip of the toe, but in 24 of these 29 patients the optical measurement was possible. Mean toe pressures at D1 were 108 +/- 45 mm Hg and D2 102 +/- 45 mm Hg, which were statistically not different. The correlation coefficient for the highest ankle artery pressure and the highest toe pressure determined by the Doppler technique was 0.389; for the highest ankle artery pressure and the toe pressure measured by the optical sensors it was 0.369, and for the toe pressures measured by Doppler technique and the optical sensors it was 0.506. Defining systolic ankle artery pressure < or = 50 to 70 mm Hg as the golden standard for CLI, the sensitivity of optical toe pressure measurement for the detection of CLI was 8%, the specificity was 96%, the positive predictive value 12%, and the negative predictive value was 94%. Independent of technique the absolute systolic toe pressures did not correlate with the absolute systolic ankle pressures. The optical measurement was more suitable for toe pressure measurement because it could be used in 90% of all patients. All in all, toe pressure measurements are more useful to exclude CLI than to prove it.

Publication Types:

• Review