H. Pylori Blood Test (Serology) Performance Characteristics
Laboratory-based validated IgG serology tests demonstrate accuracy of 90-95%, but they are inferior to urea breath testing and stool antigen testing for diagnosing active H. pylori infection. 1
Sensitivity and Specificity of Serological Testing
- Validated commercial ELISA-based IgG serology tests achieve approximately 90% specificity, though this varies considerably between different commercial products 1
- The accuracy of various commercial serological tests ranges widely, with only certain validated kits achieving >90% accuracy 1
- Rapid "office" serological blood tests perform poorly, with sensitivities ranging from 63-97% and specificities from 68-92%, making them unreliable for clinical use 1
Critical Limitations of Blood Testing
The fundamental problem with serology is that it cannot distinguish active infection from past infection, as IgG antibodies remain elevated for months to years after H. pylori has been eradicated from the stomach 1
- Antibodies against H. pylori (especially CagA) persist despite transient decreases in bacterial load and even long after bacterial clearance 1
- Serology should never be used to confirm eradication of H. pylori after treatment 2
When Serology Is Appropriate
Serology has specific clinical scenarios where it remains useful:
- When patients are currently taking proton pump inhibitors (PPIs) or antibiotics that would cause false-negative results with other tests 1
- In patients with active ulcer bleeding where bacterial load may be temporarily suppressed 1
- In cases of gastric atrophy, intestinal metaplasia, or gastric malignancies where bacterial density is permanently low 1
- When other non-invasive tests are unavailable or contraindicated 1
Superior Alternative Testing Methods
The urea breath test (UBT) is the gold standard non-invasive test, with sensitivity of 94-97% and specificity of 95-97.7%, significantly outperforming serology 2, 3
- Laboratory-based monoclonal stool antigen tests achieve sensitivity and specificity of approximately 93-97%, comparable to UBT 2
- Both UBT and stool antigen testing detect active infection and can confirm eradication 2
Key Clinical Pitfalls
- Only use validated commercial IgG ELISA tests—avoid rapid office-based serological tests due to poor accuracy 1
- Local validation of serological tests is recommended because antigenic properties of H. pylori strains vary geographically 1
- Never use serology for post-treatment confirmation, as positive results may reflect past rather than current infection 2
- If serology must be used, ensure PPIs have been stopped for at least 2 weeks before alternative testing methods (UBT or stool antigen) to avoid false negatives 1, 2