The main purpose of the study is to evaluate the acceptance and viability of self-testing using dried blood spot (DBS) testing assisted by center of origin or referral hospital, as a strategy for screening for hepatitis C virus (HCV) in high risk population (ex-users of drug dependence centers) compared to the general population assisted by primary care centers.

This is a randomized clinical trial involving patients who between 2013 and 2017 have contacted the drug dependence center and patients from general population.

After selecting those who do not meet any exclusion criteria, a letter will be sent to them inviting them to participate in this study. This letter will contain the study information sheet and informed consent, and a self-testing kit with an explanatory leaflet so that each person can carry out the test in a simple and easy way.

The main purpose of the study is to evaluate the acceptance and viability of self-testing using dried blood spot (DBS) testing, to study whether support improves participation and to identify predictors of participation.

For the present study, assuming an increase of 18% participation (from 18% to 28% offering support by the patient's referral center, and based on a previous study in our environment of self-testing in the general population), taking into account a power of 80%, alpha error of 5%, and losses of 20%, will require 346 patients per group.

Inclusion criteria:

• All subjects who have contacted a drug dependence center between 2013 and 2017, as well as patients from a group of a primary care center.
• Signed informed consent.

Exclusion criteria:

• Patient's refusal to participate in the study.
• Negative HCV serology or viral load in the last year.
• Death.
• Belonging to another health area
• Not having the patient's address in the hospital's computer system.