Is the Helicobacter pylori (H. pylori) test a blood test?

H. pylori Testing Methods

H. pylori testing is not exclusively a blood test; the preferred non-invasive diagnostic methods are urea breath tests (UBT) and stool antigen tests, which detect active infection rather than just antibodies. 1

Non-Invasive Testing Options

Serology (Blood Test)

• Serological tests detect antibodies to H. pylori in blood with sensitivity and specificity of approximately 90% 2
• Blood tests only indicate exposure to H. pylori at some point in time and cannot differentiate between active infection and previous exposure 2, 1
• Antibody levels often remain elevated after H. pylori is eliminated, making serology unsuitable for confirming eradication 2, 1
• Office-based serologic tests are less accurate than laboratory-based enzyme-linked immunosorbent assay (ELISA) tests 2
• In populations with low disease prevalence, the positive predictive value of serological tests falls dramatically 2, 1

Urea Breath Test (UBT)

• UBT is considered the gold standard non-invasive test with excellent sensitivity (94-97%) and specificity (95-100%) 3, 1
• Patient drinks a preparation containing labeled urea (13C or 14C), which is metabolized by H. pylori bacteria if present 2
• The carbon isotope is absorbed into the bloodstream and exhaled as carbon dioxide, which is then measured 2
• UBT detects active infection rather than just past exposure 1
• Prior to testing, antibiotics and bismuth should be withheld for at least 4 weeks, and PPIs for at least 7 days 2

Stool Antigen Test

• Directly detects H. pylori bacterial antigens in stool specimens with sensitivity and specificity of approximately 93% 2, 1
• Comparable accuracy to UBT for identifying H. pylori before antibiotic therapy 2
• Valuable for both initial diagnosis and confirmation of eradication 1
• Requires collection of a stool sample and laboratory analysis by trained personnel 2

Invasive Testing Methods (Requiring Endoscopy)

• Rapid urease test: Quick results during endoscopy with sensitivity 80-95% and specificity 95-100% 2, 1
• Histology: Allows visualization of bacteria and assessment of mucosal damage 2, 1
• Culture: Permits antimicrobial susceptibility testing, especially valuable after treatment failure 2
• PCR: Can detect H. pylori and antibiotic resistance directly from biopsies 2

Important Testing Considerations

• Proton pump inhibitors (PPIs) should be stopped for at least 2 weeks before testing by UBT, stool test, or invasive methods to avoid false-negative results 2, 1
• For confirmation of eradication, testing should be performed no earlier than 4 weeks after completion of treatment 3, 1
• Serology should not be used to confirm eradication after treatment 2, 3, 1
• The "test and treat" strategy using non-invasive tests is recommended for young (<50 years) dyspeptic patients without alarm symptoms 1

When to Use Each Test

• Initial diagnosis in primary care: UBT or stool antigen test are preferred 2, 1
• When patient has recently used antibiotics or PPIs: Consider validated IgG serology or wait 2 weeks after stopping these medications 1
• Confirmation of eradication: UBT or stool antigen test (not serology) 3, 1
• When endoscopy is indicated (alarm symptoms, age ≥50 with new dyspepsia, treatment failure): Invasive testing methods 1

Blood tests for H. pylori have limitations and should not be the first choice for diagnosis or for confirming eradication due to their inability to distinguish between active infection and past exposure.