This serological test measures the titer (quantity) of immunoglobulin G (IgG) antibodies against Helicobacter pylori in blood serum. These antibodies appear several weeks after the initial infection and may remain elevated for many years, even after successful treatment. Therefore, a positive result indicates past or present exposure to the bacterium, but it cannot distinguish between a current active infection and one that was treated or cured in the past. It is not typically used to assess the success of immediate treatment.