IFNL4 Genotype for Predicting Response to Ledipasvir/Sofosbuvir

Background: Hepatitis C virus (HCV) infection is a leading cause of hepatocellular carcinoma and end-stage liver disease. Ledipasvir/sofosbuvir is used to treat chronic HCV. The drug name for it is Harvoni. It is a very effective treatment, but it is expensive. Researchers have found a genetic variation that predicts how people will respond to this treatment. They want to learn more about this genetic link. It could help develop better treatments for HCV. Objective: To study if certain inherited genetic differences and other factors affect the different ways patients respond to treatment with Harvoni. Eligibility: Adults ages 18 who are members of the Kaiser Health Plan and have recently been treated for hepatitis C with Harvoni Design: Researchers will review medical records to identify a group of people who could be in the study. Participants will provide a saliva sample at home. They will get instructions and kit to collect it in. Participants will spit into a funnel until it reaches a mark on the funnel. It will be about 1 teaspoon of saliva with no bubbles. They will return the sample in a prepaid mailer. Researchers will do genetic tests on the samples. The participant data will be kept confidential. It will not be given to insurance companies. Participants will not be given any test results. ...