Helicobacter: which blood markers matter?

For Helicobacter pylori, the main blood markers are serological antibodies (IgG, IgA). A positive IgG indicates past or current infection but cannot distinguish active from resolved infection. IgA may suggest recent infection but has lower specificity. In clinical practice, serology is increasingly replaced by stool antigen tests or the 13C-urea breath test, which reliably detect active infection. A complete blood count can provide indirect clues: iron deficiency anemia without clear cause may result from H. pylori gastritis with occult bleeding. Low vitamin B12 or ferritin levels can also be associated. DNA-based blood markers (e.g., genetic variants in inflammatory pathways) are not validated for diagnosis or treatment decisions. Evidence for these blood markers comes from clinical guidelines (e.g., Maastricht V/Florence Consensus). Caveat: serology can yield false positives, especially in low-prevalence areas. If active infection is suspected, confirm with stool antigen or breath test.