05/05/2016 Siemens Advia Centaur hep C antibody result positive.08/10/2016 Abbott Architect (cmia) hep C antibody result negative. Who is telling truth?

It's not really. a question of truth telling. No test is perfect: the proteins and reactants used in each test will respond to an individual's blood/biologic material, potentially, in a different way. Falsely positive or falsely negative results are not very unusual. You need to decide on a confirmatory strategy with your doctor. Retesting is necessary and an expert can help you weigh the evidence to decide result.