Part 6: Detection and Prevention of Foot Problems in Type 2 Diabetes

Background - Peripheral Vascular Disease as a Risk FactorPeripheral vascular disease (PVD) is common in people with Type 2 diabetes beingpresent in 8% at the time of diagnosis and in 45% of people who have had diabetes for20 years (Hiatt & Sussman, 1994). The prevalence of PVD at diagnosis of diabetesand the risk of developing PVD over time increase with increasing age (Davis et al,1997).PVD is considered to be the most important factor related to outcome of a diabeticfoot ulcer (International Working Group on the Diabetic Foot, 1999) and is a majorcontributor to the high rates of amputation in people with diabetes as well aspredicting increased risk of cardiovascular mortality (Orchard & Strandness, 1993).Vascular assessment in the general practice setting is, by necessity, based on historyand clinical examination. More sophisticated bedside investigations are available andhave been shown to predict ulceration and amputation. The ankle-arm index (AAI) orankle-brachial index (ABI), is a ratio of blood pressure measured in the arm and in theankle by a hand-held ultrasound doppler. A ratio of less than 0.50 indicates severePVD. Calcification of pedal arteries, which is common in people with diabetes, resultsin a falsely high blood pressure reading in the feet and consequently a falsely highratio. In addition, the repeatability of the AAI/ABI measure has a coefficient ofvariation of 10 to 15% and therefore requires duplicate readings. In view of theequipment and time required to perform the examination, AAI/ABI may be used in aspecialist practice but has limited application in a busy general practice.Transcutaneous oximetry (TcPO 2 ) is a measurement of partial pressure of oxygen atthe skin surface. Levels less that 50mmHg are associated with PVD and a reducedhealing ability (McNeely et al, 1995).Invasive techniques such as angiography are more specific in demonstrating PVD butare also associated with significant morbidity. In a study of 104 people with diabetes,both a score based on the results of an angiogram (OR 2.32 [CI 1.40-3.84]) and theABI (OR 1.84 [CI 1.10-3.06]) were predictive of major amputation (Faglia et al,1998).Evidence - Peripheral Vascular Disease as a Risk FactorPeripheral vascular disease is a risk factor for amputationIn the prospective Seattle Diabetic Foot Study of 776 veterans with diabetes, PVD hasbeen shown to be an independent risk factor for amputation (RR 3.0, CI 1.3-7.1)(Adler et al, 1999). In a multivariate model relative to a reference hazard ratio (HR) of1 for an individual with neither PVD (as indicated by absent or diminished pulses) norneuropathy, individuals with PVD in either leg but without neuropathy had an HR foramputation of 20.5 compared with an HR of 9.3 for neuropathy alone and HR 19.0when both PVD and neuropathy were present. When different measures of PVD wereused in a multivariate hazards model, AAI ≤0.8 in either lower extremity, TcPO 2 ≤50mmHg in either foot and absence/diminished peripheral pulses gave a similar HR for21