If an ultrasound or CT scan has revealed an unexplained cyst, especially in your liver or lungs, this test is the essential next step to find the cause. The Echinococcus IgG test is a highly specialized blood test that checks for 'memory' (IgG) antibodies your immune system produces in response to the Echinococcus parasite—the tapeworm that causes hydatid disease. This test is the primary, non-invasive method to help your doctor determine if a cyst found on an image is a hydatid cyst. A simple blood draw is all that is required. Getting a precise, serological diagnosis is critical. It helps your doctor avoid invasive procedures and create the correct treatment plan from the very beginning.