EFFECT OF DIAGNOSTIC-CRITERIA ON THE PREVALENCE OF PERIPHERAL ARTERIAL-DISEASE - THE SAN-LUIS VALLEY DIABETES STUDY

Background The ankle/brachial systolic blood pressure index (ABI), a n oninvasive measure of peripheral arterial disease (PAD), is widely use d in epidemiological studies. However, the normal ranges of the ABI in healthy populations and ABI criteria for the diagnosis of PAD in larg e population studies have not been critically evaluated. Methods and R esults The San Luis Valley Diabetes Study (SLVDS) was designed to eval uate the prevalence and complications of non-insulin-dependent diabete s mellitus (NIDDM) in a biethnic population. The present study was con ducted as part of the SLVDS to assess the prevalence of vascular disea se in 1280 nondiabetic control subjects and 430 patients with NIDDM. T he ABI criteria for PAD were developed in 403 healthy individuals with a low risk for cardiovascular disease. In these low-risk subjects, th e average resting ABI value was 0.07 lower in women than in men. In bo th sexes, the dorsalis pedis ABI was 0.04 lower than in the posterior tibial artery, and the left leg ABI was 0.02 lower than the right leg ABI (all differences, P<.05). In the low-risk subjects, ABI values wer e lower after exercise than at rest and had similar differences by sex and leg as observed at rest. Using specific abnormal cutoff points fo r the ABI, we evaluated three criteria for PAD in the overall populati on: two abnormal vessels in the same leg at rest (both dorsalis pedis and posterior tibial arteries), one abnormal vessel per leg at rest, a nd an ABI abnormality only after exercise. Subjects classified with PA D by the two-vessel criterion had a higher frequency of claudication a nd the physical finding of an absent pulse compared with subjects with out PAD or patients with PAD defined by the one-vessel or exercise cri terion. Use of the two-vessel criterion identified an increased risk o f PAD with increasing age, NIDDM, smoking, hypertension, and elevated cholesterol levels. In contrast, the one-vessel PAD criterion was asso ciated only with increasing age and smoking, and exercise-diagnosed PA D was not associated with any cardiovascular risk factor except for ma le sex. Conclusions In low-risk subjects, the normal distribution and lower abnormal cutoff point values of the ABI differed by type of test , sex, ankle vessel, and leg. When these specific abnormal cutoff poin ts were applied to the SLVDS population, the two-vessel abnormal crite rion described patients with typical clinical characteristics of PAD a nd the expected associations of PAD with cardiovascular risk factors. These clinical characteristics and cardiovascular risk factor associat ions were less evident with PAD diagnosed by the one-vessel or exercis e criterion. Therefore, an abnormal dorsalis pedis and posterior tibia l ABI in the same leg at rest should be used for the diagnosis of PAD in epidemiological studies.