BMC Public Health 2007, 7:348 http://www.biomedcentral.com/1471-2458/7/348 The diagnostic criteria of peripheral arterial disease will be considered as an AAI < 0.90, determined by portable Doppler (8 Mhz probe) measured twice by trained personnel. Cardiovascular risk will be calculated with the Framingham-Wilson tables, with Framingham calibrated by the REGICOR and SCORE groups. The subjects included will be evaluted every 6 months by telephone interview and the clnical history and death registries will be reviewed. The appearance of the following cardiovascular events will be considered as variables of response: transitory ischaemic accident, ictus, angina, myocardial infartction, symptomatic abdominal aneurysm and vascular mortality. Discussion: In this study we hope to determine the prevalence of peripheral arterial disease, especially the silent forms, in the general population and establish its relationship with cardiovascular morbimortality. A low AAI may be a better marker of arterial disease than the classical cardiovascular risk factors and may, therefore, contribute to improving the predictive value of the equations of cardiovascular risk and thereby allowing optimisation of multifactorial treatment of atherosclerotic disease. Background Prevention and early diagnosis of atheroslerotic disease is one of the essential objectives of the field of cardiovascu- lar disease since it is the main cause of mortality in devel- oped countries. In Spain, cardiovascular diseases are the first cause of death, producing 34% of all deaths [1], with ischaemic heart disease causing the greatest number of cardiovascular deaths (31%) followed by cerebrovascular disease (29%) [1]. Atherosclerosis is currently considered a chronic, progres- sive, systemic disease, the genesis of which involves com- plicated pathogenic mechanisms. This disease is characterised by remaining clinically silent during most of its evolutive process until the sudden appearance of com- plications of the atherosclerotic plaques which lead to ischaemic vascular events. From primary prevention point of view, it is therefore very important to develop strategies to identify patients with subclinical stages of arteriosclero- sis. Atherosclerotic disease is characterised by a multifactorial aetiology constituted by different risk factors which potentiate among themselves and which are often pre- sented in asssociation [2]. Risk factors which may be mod- ified include arterial hypertension, hypercholesterolemia, diabetes mellitus, and smoking, while age and sex are non modifiable factors. Other risk factors act through interme- diate risk factors such as abdominal obesity [3,4], seden- tarism, or a family history of early coronary heart disease. These risk factors have been integrated in prediction tables based on regression models with the aim of detecting the population at high risk of presenting cardiovascular events [5]. However, the sensitivity and positive predictive value of these tables is low and, thus, most cardiovascular diseases are produced in persons without a high risk [5]. It is, therefore, important to develop markers of silent ate- riosclerotic disease which may aid to better define the patients at high risk and to thereby act early and inten- sively to prevent the appearance of cardiovascular diseases with pharmacologic and non pharmacologic measures. The ankle-arm index (AAI) is the result of the quotient obtained by dividing systolic arterial pressure (SAP) at the level of the posterior pedial or tibial artery between the brachial SAP by Doppler [6]. Low values of AAI determi- nation (<0.9) allow the diagnosis of peripheral arterial disease (PAD) in asymptomatic patients [7]. An AAI of < 0.9 has a sensitivity of 95% and a specificity of 99% for angiographically demonstrated PAD [8]. Determination of the AAI also allows the quantification of the severity of PAD: mild (AAI = 0.7 – 0.9), moderate (AAI = 0.5 – 0.69) and severe stenosis (AAI = <0.5). In some studies a low AAI has shown to be a good marker of vascular events [8]. In the Atherosclerosis Risk in Com- munities (ARIC) Study [9,10], the AAI was inversely asso- ciated with coronary disease, ictus and atherosclerosis at the level of the carotid and popliteal arteries. The Edin- burgh Artery Study [11] reported a relative risk of ictus of 1.98 (CI 95%; 1.05 – 3.77) in patients with an AAI < 0.9. In a Swedish cohort of males over the age of 68 years [12] followed over 10 years, the relative risk of ischaemic ictus for an AAI = 0.9 was 2.0 (95% CI; 1.1 – 3.7). These results, however, do not agree in all studies. In the Cardiovascular Health Study [7], an assocation was found between a low AAI and the risk of vascular events in general, but no rela- tionship was observed between an AAI < 0.9 and the risk of ictus. In addition, in the Pittsburgh study the risk of car- diovasscular events significantly increased only above an AAI < 0.7 [13]. Another aspect requiring clarification is the prognostic value of AAI in a medium with a low prevalence of cardi- ovascular diseases such as in Spain and other Mediterra- nean countries [14]. Page 2 of 7 (page number not for citation purposes)