How accurate is h pylori blood test to pick up a previous or active infection?previous test was negative having another one.

Prior infection: The H pylori blood test is best to detect a prior infection because it detects antibodies that the body has formed. To detect an active infection, one of the best (and easiest) methods is to get a stool antigen test performed. This test looks for the actual H pylori bacteria itself. If you had a prior infection but not an active one, it should be negative.