Diagnosis and Treatment of Helicobacter pylori Using Serology Tests
Serology tests are not recommended as the primary diagnostic method for H. pylori infection due to their inability to distinguish between active infection and past exposure, with stool antigen tests or urea breath tests being the preferred non-invasive diagnostic methods. 1
Diagnostic Methods for H. pylori
Serology Testing Limitations
- Serological tests detect anti-H. pylori IgG antibodies in serum but cannot distinguish between active infection and previous exposure 1
- Antibody levels persist in blood for long periods, leading to false-positive results in previously treated patients 1
- 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
- Serology tests should not be used to confirm eradication after treatment as antibodies remain elevated after H. pylori elimination 1
Recommended Non-invasive Tests
- Urea Breath Test (UBT) is considered the most accurate non-invasive test with excellent sensitivity (94.7-97%) and specificity (95-95.7%) 2
- Stool Antigen Test directly detects H. pylori bacterial antigens in stool specimens with sensitivity and specificity of approximately 93%, comparable to UBT 3
- Both UBT and stool antigen tests detect active infection rather than just past exposure, making them valuable for both initial diagnosis and confirmation of eradication 3, 2
Clinical Considerations for Testing
- For optimal accuracy, patients should fast for at least 6 hours before UBT 2
- False negative results can occur with both UBT and stool antigen tests if patients have recently taken antibiotics, bismuth compounds, or proton pump inhibitors 1
- These medications should be discontinued at least 2 weeks before testing to avoid false negatives 1
- The "test and treat" strategy using non-invasive tests is recommended for young (<50 years) dyspeptic patients without alarm symptoms 1, 2
Treatment of H. pylori Infection
First-line Treatment Options
- Triple therapy: Omeprazole 20 mg twice daily + clarithromycin 500 mg twice daily + amoxicillin 1 g twice daily for 10 days 4
- Dual therapy: Omeprazole 40 mg once daily + clarithromycin 500 mg three times daily for 14 days, followed by omeprazole 20 mg once daily for another 14 days 4
- Alternatively, amoxicillin 1 g and lansoprazole 30 mg, each given three times daily for 14 days 5
Eradication Confirmation
- Eradication should be confirmed at least 4 weeks after completion of treatment 6
- Patients should be off proton pump inhibitors for at least 7 days and antibiotics/bismuth for at least 4 weeks before confirmation testing 1
- UBT or stool antigen test is recommended for confirmation rather than serology 1
Special Considerations
When Serology May Be Useful
- Large epidemiologic surveys and population screening in high-prevalence areas 1
- Studies on age at acquisition of infection 1
- When other tests might be falsely negative (e.g., recent use of antibiotics or PPIs) and clinical suspicion is high 1
- In research settings for assessment of antibodies against CagA and VacA proteins 1
Pitfalls to Avoid
- Do not use serology tests to confirm eradication within 6-12 months after treatment 7
- Do not rely solely on office-based serologic tests as they are less accurate than laboratory-based ELISA tests 1
- Recognize that the positive predictive value of serology tests falls dramatically in populations with low disease prevalence 1
- Avoid using serology in patients who have previously received H. pylori eradication therapy 7
Endoscopy Indications
- Patients with alarm symptoms (bleeding, weight loss) 1
- Older patients with new-onset dyspepsia 1
- Patients who have failed eradication therapy and need culture and antimicrobial sensitivity testing 1
By following these evidence-based recommendations for diagnosis and treatment of H. pylori infection, clinicians can optimize patient outcomes while minimizing unnecessary testing and treatment failures.