Serologic tests are blood tests that look for antibodies in your blood. They can involve a number of laboratory techniques. Different types of serologic tests are used to diagnose various disease conditions.Serologic tests have one thing in common. They all focus on proteins made by your immune system. This vital body system helps keep you healthy by destroying foreign invaders that can make you ill. The process for having the test is the same regardless of which technique the laboratory uses during serologic testing.The immune system defends against antigens by producing antibodies. These antibodies are particles that attach to the antigens and deactivate them. When your doctor tests your blood, they can identify the type of antibodies and antigens that are in your blood sample, and identify the type of infection you have.Sometimes the body mistakes its own healthy tissue for outside invaders and produces unnecessary antibodies. This is known as an autoimmune disorder. Serologic testing can detect these antibodies and help your doctor diagnose an autoimmune disorder.