Patient: The blood test for HP is positive, but the breath test is negative, what is going on? The first People’s Hospital of Shanghai, Department of Gastroenterology, Jing Da Dao: The blood test for HP in the unit physical examination mostly refers to the antibodies to H. pylori in the blood, namely Hp-Ab. A positive Hp-Ab indicates that the body has been infected with Hp, but not necessarily that there is still Hp infection in the stomach, because even if Hp is eradicated, the antibodies can remain in the body for a long time. If the breath test is positive, it indicates that the patient currently has Hp infection in the stomach; if it is negative and has not taken antibiotics, bismuth (such as bismuth in gum) and acid suppressants (such as omeprazole and famotidine) in the month prior to the breath test, it indicates that there is no Hp infection in the stomach.