The hypothesis of this investigation stresses that the current understanding of the prevalence of HCV infection in the general population and in different subgroups will serve to lay out medium- and long-term measures for action geared toward reducing the disease burden through preventive, research, screening and therapeutic measures.

Aim: To determine the prevalence of seropositivity and chronic infection with the HCV and to analyze the associated factors. To analyze and infer different screening strategies for HCV infection based on the at-risk groups/cohorts of elevated prevalence detected. to assess the efficiency of screening strategies and the subsequent cost-effectiveness of treatment in the general population

Design of the study: Seroepidemiological and virological study of cross-sectional population-based.

Patients and sampling: The study population has been distributed in groups according to age (20-34; 35-49; 50-74 years) and sex. In order to select a representative sample of this overall population, three Spanish regions will be selected on the basis of their different HCV-related hospitalisation rates defined as follows: high, >120 cases/100,000 inhabitants (Madrid); medium, 90-119 cases/100,000 inhabitants (Cantabria); or low, <90 cases/100,000 inhabitants (Valencia).

The participants will be selected through a random, representative sample using our two-stage conglomerate sampling with stratification of the First-Stage Units. These FSUs are made up by the Basic Health Areas (Health Centers). The Second-Stage Units are made up by the individuals. The stratification criteria used in the first stage will be the socioeconomic status-rural/urban environment. The selection of sample elements will be carried out through simple random sampling from the healthcare card database pertaining to the selected Health Centers. A sequence of random, computer-generated numbers will be obtained.

Sample size: In order to achieve an accuracy of 0.4% in the estimate of a percentage through a two-tailed 95% confidence interval, assuming the prevalences indicated by age strata in the general Spanish population (0.6%, 1.9% and 2.7% respectively), a total of 12,263 subjects distributed as follows: 1,456 aged 20-34 years, 4,476 aged 35-49 years and 6,331 aged 50-74 years.

Anticipating an uptake of 9-15%,21 following invitation via telephone, between 81,753 and 136,255 subjects distributed over the three regions needed to be contacted at random.

Recruitment method for randomized patients. Selected subjects will be called by phone by trained personnel. The subject will be invited to report for an interview in order to carry out a socio-healthcare questionnaire, a physical examination, and an analytical test. In the event the patient refuses to participate, permission shall be requested to collect minimum anonymous data for the subsequent study of possible screening biases. Patients meeting inclusion criteria and provide written informed consent to be included in the study.

Variables in the study: socio-healthcare questionnaire includes variables such as age, sex, socioeconomic status, risk factors, health habits, etc. Analytical variables (blood count, biochemistry, serologies for HBV and HCV, etc.) are collected. A Fibroscan is also performed. A cost-effectiveness of screening strategies and treatment will be analysed using a Markov model

Full duration: 21 months

Inclusion Criteria:

• Patients between 20 and 74 who have health card in each of the autonomous communities studied.
• They agree to participate, understand and give informed consent.

Exclusion Criteria:

• Do not meet the criteria above.

General population aged 20-74 years who agree to participate when contacted by phone call after a two-stage conglomerate sampling with stratification of the First-Stage Units.

The study will be carried out in three Autonomous Communities (regions) in Spain.