We will carry out a observational analytical, population-based, multicentre study of cases and controls attending primary healthcare centers in the North Barcelona and Maresme area. The study has been approved by the Ethical Committee of Clinical Investigation, Jordi Gol i Gurina Foundation.
Study subjects
This will be a multicentre study including the participation of 18 primary care teams covering a population of 360,000 inhabitants of an urban, and semi-rural zone of North Barcelona and Maresme, Spain.
Definition of cases
All adult patients fulfilling inclusion criteria in whom fatty liver is detected by means of ultrasonography performed for any reason in the reference Department of Radiology at the beginning of the study and have not received previous treatment for NAFL. Subjects will be considered as cases if they present fatty liver defined according to the standard criteria accepted by the American Gastroenterology Association: An Increase in hepatic echogenicity taking renal echogenicity as a reference, the presence of enhancement and lack of differentiation in periportal intensity and the vesicular wall due to great hyperechogenicity of the parenchyma. The degree of involvement will be standardized with a semiquantitative scale of the degree of hepatic enhancement.
Definition of controls
For every case an age (± 5 years) and sex-matched control will be selected from the same primary care centre by the same health care team. The controls will be selected from the SIAP (Primary Care Information System), a database that collects all the people that belong to one primary care center. This database in more complete and more updated than the population census. The controls will be invited to voluntarily participate and informed consent will be obtained for performing ultrasonography and analytical tests to ensure the absence of manifest hepatic disease. Subjects with normal ultrasonography results without alterations of hepatic enhancement will be considered as controls.
Inclusion criteria
Adults of both sexes from these Primary Care teams between the age 15 and 80 years who wish to voluntarily participate in the study and who have signed a written informed consent form to participate.
Exclusion criteria
Alcohol intake > 30 g/day in males and > 20 g/day in females. Presence of chronic liver disease. Presence of the hepatitis B virus surface antigen or the presence of virus hepatitis C antibodies. Subjects with conditions or diseases hindering data collection and follow up of the study such as incapacitating diseases, cognitive deterioration, institutionalized patients or subjects with no fixed address in any of the basic areas of the study. Subjects who do not provide written informed consent to participate in the study. The cases and controls with any exclusion criteria in their clinical history will not be invited to participate.
Variables
The following covariables will be evaluated in the patients fulfilling the inclusion criteria and who accept to participate in the study.
1. Sociodemographic variables: Age, sex, occupation, education and place of residence.
2. Clinical history including:
2.1. Personal history of liver disease, biliary lithiasis, surgical interventions.
2.2. Presence of comorbidities: Obesity and being overweight, type 2 diabetes, dyslipemia and arterial hypertension.
2.3. Alcohol intake: We will determine the type and quantity of alcoholic beverages consumed. The beverages consumed will be calculated per unit of standard beverage (glasses), differentiating the consumption between working days and the weekend. This will allow the calculation of the unit of standard beverage for each patient. Furthermore, the personal history of each case will be reviewed to rule out the possible history of high beverage consumption.
2.4. Smoking habit.
2.5. Habitual drug use: history of drug use during previous six months.
3. Physical examination:
3.1. Anthropometric data: weight, height, abdominal obesity and body mass index. The measurement of abdominal obesity will be done through the determination of the waist and hip circumferences using a tape measure (waist circumference will be considered the intermediate abdominal area perimeter between the last costal arch and the iliac crest measured in the horizontal plane, and hip circumference as that obtained in the plane of maximum relief of the gluteus muscles). The body mass index will be calculated according to the classical weight formula (kg/height m2).
3.2. Determination of arterial pressure: This will be determined with a validated automatic tensitometer with the subject resting. Three determinations will be carried out, separated by two minutes, and the final arterial pressure will be the average of the last two determinations discarding the first reading.
4. Analytical determinations:
4.1. Blood analyses will include: a complete haemogram, glycaemia, glycosylated haemoglobyn, urea, creatinine, uric acid, a lipid study (cholesterol, triglycerides, HDL, LDL), and liver function tests, including hepatitis markers (hepatitis B surface antigen virus and hepatitis C virus antibodies).
4.2. Baseline insulin levels will be determined by the immunochemoluminescence method.
4.3. Determination of insulin resistance will be established with the HOMA method (homeostasis model assessment). ([glycaemia (mmol/L) x insulin (mU/L)]/22.5).
4.4. A sample of the first urine in the morning will be taken to determine microalbuminuria.
4.5. Special analytical determinations: Frozen serum from all patients will be kept to determine different fibrotic markers (hyaluronic acid, leptin, adiponectin, TNF-alfa).
5. Determination of the different fibrotic indexes (HAIR score [
12], NAFLD fibrosis score [
13]).
6. Diagnosis of the metabolic syndrome: This will be made according to the criteria of the WHO modified by the European Group for the Study of Insulin Resistance (EGIR)[
15], the Adult Treatment Panel III (ATP-III) of the National Cholesterol Education Program (NCEP) [
16] and the International Federation of Diabetes [
17].