Blood tests check your blood to see if you have antibodies which stick to H. pylori. If antibodies are present, it means that either you have a current infection of H. pylori OR you have had an infection of H.pylori in the recent past (i.e. the past 3 years usually). To have this test done your doctor can draw a blood sample and send it to a lab to have it tested. Many national labs perform this test. However if the blood test is negative you can be reassured that you never had and you do not have an H.pylori infection. By the same token if your blood test is positive you cannot be certain that you have a current active H.pylori infection. Only a breath test will clearly indicate whether you have a current infection.
Recently, several companies have been working on rapid blood tests for H. pylori which your doctor can do in a few minutes in his office. Saliva tests to detect antibodies in saliva have also been described. However these are not very accurate.
Please Note: Antibody tests do not work well after you have been treated. The reason for this is that antibodies to H.pylori decline slowly and may remain elevated after H. pylori has been totally eradicated.. However, antibody tests are not affected much if you have taken antibiotics, Pepto-Bismol, Proton pump inhibitors (such as Prilosec, Zoton, Losec, Pariet Nexium, Somac etc.), cytoprotectives (such as Carafate,& sucralfate) and H2 receptor antagonists (such as Zantac, Tagamet,) in the last month.