BMC Public Health 2007, 7:348 http://www.biomedcentral.com/1471-2458/7/348 Moreover, the PAD is a significant predictor of cardiovas- cular mortality [15-17]. Mortality is also greater in patients with asymptomatic PAD compared to patients without arterial disease [16,18,19]. Some studies [7] have suggested that PAD in females represents a greater cardio- vascular morbidity while in males this disease represents a higher mortality rate. The prevalence of PAD ranges between 1.8% and 25% according to the population, the medium studied and the cut-off value of the AAI [11,20-25]. Likewise, the preva- lence is higher in determined populational subgroups such as diabetics [20] and smokers [23]. No populational based studies are available in Spain, with the studies found being carried out in selected populations [26-34]. The present study will have two phases. The main objec- tive of the first phase (cross-over study) is to determine the prevalence of PAD in the general population, in both its silent and symptomatic forms. The secondary objective is to study the association of PAD, especially in the silent forms, with other prevalent cardiovascular events and car- diovascular risk factors. The main objective of the second phase (cohort study) is to determine the incidence of car- diovascular events in patients with PAD and quantify the risk of having these events. The secondary objective in this phase is to study the predictive value of AAI with respect to the risk of having cardiovascular events in relation to the equations of cardiovascular risk (Framingham-Wil- son, Framingham calibrated by REGICOR and SCORE). Methods/Design This is a two-phase study. The first phase is a transversal, multicentre, descriptive study the aim of which is to deter- mine the prevalence of symptomatic and asymptomatic PAD in a general population attended in primary care. The secondary aim is to study the association of PAD, espe- cially in the silient forms, with other previous or prevalent cardiovascular events and cardiovascular risk factors. The second phase is a cohort study, the main objectives of which are to determine the incidence of cardiovascular events in patients with and without PAD and to quantify the risk of having these events. The secondary objective is to study the predictive value of AAI with respect to the risk of having cardiovascular events in relation to the equa- tions of cardiovascular risk (Framingham, Framinham calibrated by REGICOR and SCORE). An initial 5-year fol- low up will be carried out in the cohorts generated in phase I: subjects without PAD and subjects with PAD and the cardiovascular morbimortality will be analysed. This study has been approved by the local Ethics Committee (Jordi Gol i Gurina Foundation of Investigation in Pri- mary Care). Informed written consent will be obtained from all the participants. Likewise, the recommendations of the World Medical Assocation Declaration of Helsinki will be followed [35]. Setting This study will be performed in a total of 24 healthcare centres within the metropolitan area of the city of Barce- lona and the county of North Barcelona – Maresme, including urban and semi-rural healthcare centres. These centres cover a population of approximately 600,000 inhabitants. Study Population and subjects A simple randomised sample will be undertaken until achieving the required sample size. Figure 1 provides a flow diagram of the study. Data collection Data will be collected in a questionnaire specifically designed for this study. Prior to initiation of the study a pilot trial will be performed in 120 cases to detect errors in its design, to test the questionnaire interviewers and to verify concordance in data collection (data validation). Baseline data collections (cross-over study) The following variables will be studied. -Demographic, cultural and economic variables related to the capacity of physical strength, with a previously vali- dated questionnaire [36], related to menopause, family history of early cardiovascular death, personal history of cardiovascular disease, acute myocardial infarction, angina, cerebrovascular accident [14]. Similarly, the clini- cal history will be verified if the patient is diagnosed with ictus (CIE 10 code: I64), transitory ischaemic accidents (CIE 10 code: G45), angina (CIE 10 code: I20.0), acute myocardial infarction (CIE 10 code: I25) and PAD of the lower extremities (CIE 10 code: I73.9). Personal history of hypercholesterolemia, diabetes mellitus, arterial hyper- tension and smoking, establishing the history and current status of the smoking habit in the latter case [14,37-39]. -Anthropometric variables, current systolic/diastolic blood pressure values, blood analysis (total cholesterol, HDL-cholesterol, DLD-cholesterol, triglycerides and gly- caemia [glycosylated haemoglobin (HbA1c) in diabetics], except in the case of having a recent analysis within the last 12 months, and standard electrocardiogramme [40]. Calculation of cardiovascular risk with the Framingham- Wilson equations [40], Framingham calibrated by the REGICOR [41] and SCORE [42] groups, and medications taken considering current drug intake (at least 1 tablet/ day) of the following pharmacological groups: lipid-low- ering drugs, antiaggregants, anticoagulants, antihyperten- sives and hypoglycidemiants [43,44]; Edinburgh vascular questionnaire [45]. Page 3 of 7 (page number not for citation purposes)