Is there a blood test for Helicobacter pylori (H. pylori) infection?

Blood Tests for H. pylori: Available but Not Recommended

Yes, blood tests for H. pylori exist and detect IgG antibodies against the bacteria, but they should NOT be used as your primary diagnostic method because they cannot distinguish between active infection and past exposure, with an overall accuracy of only 78%. 1

Why Blood Tests Are Problematic

Serological (blood) tests have critical limitations that make them unsuitable for routine clinical use:

• Antibodies persist in blood for months to years after H. pylori has been eradicated, leading to false-positive results in previously treated patients 1, 2
• The overall accuracy of commercial ELISA serology tests averages only 78% (range 68-82%), which is inadequate for clinical use on both clinical and economic grounds 1
• Blood tests cannot be used to confirm eradication after treatment since antibodies remain elevated even after successful elimination of the bacteria 1, 2
• The positive predictive value falls dramatically in populations with low disease prevalence 1

Recommended Diagnostic Tests Instead

Use the Urea Breath Test (UBT) or Stool Antigen Test as your first-line diagnostic methods:

• Urea Breath Test has excellent sensitivity (94.7-97%) and specificity (95-95.7%), making it the most accurate non-invasive test 1, 2
• Stool Antigen Test (laboratory-based monoclonal antibody test) has sensitivity and specificity of approximately 93%, comparable to UBT 1, 2
• Both tests detect active infection rather than just past exposure, making them valuable for both initial diagnosis and confirmation of eradication 1, 2

Limited Situations Where Blood Tests May Be Acceptable

Serology may be considered only in these specific circumstances:

• When patients have recently used antibiotics, bismuth products, or proton pump inhibitors (PPIs) and medication washout is not possible, as serology is the only test not affected by these medications 1, 2
• In patients with gastric atrophy, gastric malignancies, or ulcer bleeding where other tests might be falsely negative due to low bacterial load 1
• For large epidemiologic surveys and population screening in high-prevalence areas 1

Critical Testing Considerations to Avoid False Results

Before performing UBT or stool antigen testing:

• Stop PPIs for at least 2 weeks (preferably 7-14 days) before testing 1, 3
• Stop antibiotics and bismuth for at least 4 weeks before testing 1, 2
• For confirmation of eradication, wait at least 4 weeks after completing treatment before testing 1, 2

Rapid In-Office Blood Tests: Even Worse

Avoid rapid in-office whole blood fingerstick tests:

• Near-patient blood tests have mean sensitivity of only 71.1% and specificity of 87.6%, considerably lower than originally assumed 4
• Finger-prick test results can vary when there is difficulty obtaining blood, as squeezing the finger changes the hematocrit by mixing tissue fluid with the blood sample 4
• Rapid in-office serological tests have limited accuracy and should be avoided 1, 2

Practical Algorithm for H. pylori Testing

For patients under 50-55 years without alarm symptoms (bleeding, weight loss, dysphagia):

• First choice: 13C-Urea Breath Test or laboratory-based monoclonal stool antigen test 1, 2
• If patient recently used antibiotics or PPIs and cannot wait for washout period: Consider validated IgG serology as a last resort 1, 2

For patients over 50-55 years or with alarm symptoms:

• Proceed directly to endoscopy with invasive testing (rapid urease test, histology, or culture) 1