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Study Design and Examination Schedule

Detailed information on the design of the SCAPIS study have been described by G Bergström et al in J Intern Med 2014.

In short, SCAPIS will recruit approximately 30,000 randomly selected men and women aged 50 to 65 years. The recruitment and examinations will be performed at six university hospitals (Uppsala, Umeå, Linköping, Malmö/Lund, Gothenburg and Stockholm). The study examinations are performed on two to three separate days separated by one to two weeks and divided into:

Core Examinations – collected at all sites

Questionnaire

The questionnaire uses a total of 150 questions separated in validated sets relating to dimensions central to the research aims. Detailed information on diet, environmental and lifestyle factors as well as data on psychosocial well-being, socioeconomic status and other social determinants are collected.

Anthropometry, ECG, blood pressure and physical activity

Standard anthropometric data as well as blood pressure and ECG measurements are collected. Physical activity is measured by accelerometer testing for seven days.

Imaging and functional tests relating to the cardiovascular system

To assess the status of the three major vascular beds involved in cerebral, cardiac and peripheral artery disease, we use CT angiography for coronary disease, ultrasound and magnetic resonance imaging (MRI) for carotid disease and ankle-brachial index for peripheral artery disease.

The coronary circulation is assessed directly with CT angiography using contrast injection and high-frequency imaging (Motoyama, JACC 2009). We also measure the calcium content in each coronary artery. CT angiography is extremely powerful and gives information on morphology of calcified and non-calcified plaques and their lumen obstruction as well as remodeling of lumen geometry, information that is not provided by conventional intra-arterial angiography.

Ultrasound is the best validated noninvasive technique to detect, quantify and stage subclinical atherosclerosis in the carotid arteries (Mathiesen, Circulation 2001; Spence, Nat Clin Pract Neurol 2006). In addition to plaque size and number, the grey-scale of the 2D plaque image and its distribution can be used to differentiate homogenous vs. heterogeneous structures and low vs. high echogenicity. Patients with moderate to large plaques in their carotid arteries are asked to participate in a third visit for an MRI to get in-depth information on plaque inflammation, lipid-rich necrotic core, thick fibrous cap, intra-plaque hemorrhage, and plaque volume (Corti, Euro Heart J 2011).

Imaging and function tests relating to the lung

Early structural changes in lung tissue are imaged using a high-resolution CT scan over the full lung volume (Heussel, Eur Radiol 2009). This provides information on airway wall thickness and emphysema and thereby essential information in the phenotyping of COPD.

Dynamic spirometry is used according to the protocol of the BOLD study to measure forced expiratory volume and forced vital capacity, and also includes a slow vital capacity maneuver (Buist, Lancet 2007.). Spirometry is performed 15 minutes after the subjects have inhaled 400 μg of salbutamol. Carbon monoxide diffusion capacity is also measured.

Imaging tests relating to metabolism

One of the unique strengths of SCAPIS is that it combines vascular and lung imaging with CT imaging of epicardial, intra-abdominal, intramuscular and intrahepatic fat deposits (Kullberg, Int J Obes 2007). In addition, the liver will be imaged using dual-energy CT; this approach allows us to identify excess iron stores in the liver, a sign of steatosis (Deugnier, World J Gastroenterol 2007).

Blood sample

100 ml venous blood sample is collected from each participants in the fasting state. Immediate analyses of cholesterol, HDL, LDL, triglycerides, , glucose, HbA1c, hsCRP and creatinine. Remaining blood is biobanked for future analyses.

Additional examinations – performed at one or more sites

In addition to core examinations, each site can expand on its own research interests by adding additional examinations as long as these does not interfere with core examinations.

Follow-up and use of National populations registries

The SCAPIS database will be enriched for years to come with detailed unbiased information by linking the database with Swedish population registries. Endpoints (myocardial infarction or cardiac interventions, stroke and exacerbation of COPD) will be identified annually by linking the unique Swedish personal identification numbers to the Swedish National Hospital Discharge Register and the Swedish Cause of Death Register and other national registers such as the Pharmaceutical Register of Prescribed Drugs. The external and internal validity of these registers are high (Ludvigsson, BMC Public Health 2011). Data from national quality registers (e.g. SWEDHEART, Riks-STROKE) will be used to retrive more detailed information on the type of event and interventions used.

Ethical considerations and approval by authorities

SCAPIS has been evaluated and approved by the ethics committee as a multi-centre study (Umeå, February 21, 2011). The local radiation committees approve the use of radiation. In addition to these formal approvals SCAPIS strives to broaden the knowledge of ethical aspects of performing large scale epidemiological studies with detailed phenotyping. SCAPIS has therefore initiated a scientific program addressing these issues.