Stool Antigen Testing: critical factors to consider.

Background and Clinical Significance

•  H. pylori is a spiral-shaped Gram negative bacterium that infects about 3 billion people worldwide 
•  Most people are infected as children
• Colonizes the stomach and duodenum indefinitely 
•  Infection increases linearly with age > 40% age over 60 years
•  HP has been classified as group I carcinogen for gastric carcinoma by the World Health Organization 
•  HP-infected individual has 2-8 times higher risk of gastric carcinoma than the general population 
•  Stomach cancer causes about 800,000 deaths worldwide per year

 Common in East Asia and Eastern Europe World Cancer Report 2014. World Health Organization

Mode of transmission:

•  fecal-oral 
•  person to person 
• contaminated water 
•  contaminated food 
•  zoonotic – (domestic cats, primates, sheep)

Clinical Outcomes of Helicobacter pylori infections

• Greater than  80% of people infected will be asymptomatic 
•  15 - 20%  will suffer from chronic gastritis, gastric ulcer or duodenal ulcer
• Less than 1% of people will develop gastric cancer

Source: Dr. Hagmeyer
https://drhagmeyer.com/the-damaging-effects-of-h-pylori/

The prevalence rates of Helicobacter pylori (H. pylori) infection in the US

60% of Hispanics, 54% of African Americans, and  20% Caucasians are affected.

•  New Mexico 15-20% 
• New York 15-20% S
• outh Carolina ≥20% 
• Puerto Rico ≥20% 
• llinois 15-20% 

Sonnenberg et al. (2010). A National Study of Helicobactor pylori Infection in Gastric Biopsy Specimens

 

Prevalence of H. pylori in Africa and East Asia

Why Stool Antigen Testing?

•  Simple 
• Cost-effective 
• High Sensitivity and Specificity 

 Purpose

• Diagnose an active infection
•  Confirm eradication of H. pylori after treatment
• Eradication reduces risk of gastric cancer

 Pit falls

•  False negative result in patients who are taking PPIs antibiotics or bismuth 
•  Inadequate sample volume 
•  False positive result in patients with acute upper gastrointestinal bleeding 
•  H. pylori antigen testing appears to be more accurate at detecting eradication when performed 4 - 8 weeks

 Data Interpretation

 Why cut-off value?

•  H pylori is genetically highly diverse
•  Several strains, variation in virulence factors depending on geographic location

CagA gene differs between isolates from East Asia versus Europe and North America iceA1 found in Asian countries; iceA2 found in Western countries Particular variants of vacA, such as vacA s1/m1 restricted to East Asia. (Shiota et al., 2013)

• Cut-off values for EIA testing set by manufacturers not representative of samples

 Other Factors to Consider

• Country of origin/birth Geographic location and prevalence of H. pylori 
• Age 
• Frequency of travel
• Travel destination

Robin Warren (left) Barry Marshal(right). Won the Nobel prize in physiology in 2005 for their discovery of H. pylori in 1981. 

To treat or not to treat: Helicobacter pylori: Friend or foe?

• Antibiotic Resistance Adverse effects- anaphylaxis Clostridium difficile infection
•  Treatment tops $32 billion in the US 
• Protection from gastroesophageal reflux disease and esophageal adenocarcinoma 
• H. pylori has been colonizing the human stomach for more than 58,000 years 
• What if you alter the colonization of the fecal microbiome? 
• Inverse relationship between H. pylori infection and asthma, allergies (Malnick et al., 2014) Possible protection from Multiple Sclerosis (Mohebi et al., 2013) 

References

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 2. Suzuki R, Shiota S, Yamaoka Y. Molecular epidemiology, population genetics, and pathogenic role of Helicobacter pylori. Infection, Genetics and Evolution. 2012;12(2):203-213. doi:10.1016/j.meegid.2011.12.002
  3. Ranjbar R, Khamesipour F, Jonaidi‐Jafari N, Rahimi E. Helicobacter pylori isolated from Iranian drinking water: vacA, cagA, iceA, oipA and babA2genotype status and antimicrobial resistance properties. FEBS Open Bio. 2016;6(5):433-441. doi:10.1002/2211-5463.12054
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 13. Mohebi N, Mamarabadi M, Moghaddasi M. Relation of Helicobacter Pylori Infection and Multiple Sclerosis in Iranian Patients. Neurology International. 2013;5(2):e10. doi:10.4081/ni.2013.e10.
 14. Tveit AH, Bruce MG, Bruden DL, et al. Alaska Sentinel Surveillance Study of Helicobacter pylori Isolates from Alaska Native Persons from 2000 to 2008. Journal of Clinical Microbiology. 2011;49(10):3638-3643. doi:10.1128/JCM.01067-11.
 15. Stewart VR, Wild CP. World Cancer Report 2014. In: Stewart VR, Wild CP. Cancer by organ site. Geneva, Switzerland: IARC Publications; 2014.