On Active Infection Testing...
Flow chart adopted from AGA1 2005 Fig 2 combined with updated Retest Guidelines from the ACG2 2007.
Patients suspected of having an H. pylori infection should be tested with a non-invasive test for active infection prior to prescribing PPIs. Passive tests (ie, serology) do not distinguish between current infection and past exposure (past cured infection)
Testing should precede treatment (no one should receive antibiotics without being tested for H. pylori infection first)
Testing should only be performed in patients who will be administered treatment
H. pylori Stool Antigen (HpSA®) Test by enzyme immunoassay or immunochromatography is one of the simplest and least expensive methods available. Results of the stool antigen test aid in the definitive diagnosis of active H. pylori infection, can be used to monitor response during and post treatment, and can confirm eradication of H. pylori. The stool antigen test can be used with patients of all ages and does not have any patient restrictions. Patients do not need to be off proton pump inhibitors, H2 blockers, or bismuth before testing.
Urea Breath Test – The Urea Breath Test (UBT) measures the 13C-labeled carbon dioxide formed in the stomach when the urease produced by H. pylori breaks down a sample of 13C-labeled urea. Breath testing requires the patient to fast before ingesting a standard sample of labeled 13C and, at a predetermined time (approx. 1 hr), produce a breath sample. After collection, the breath sample is analyzed by a mass spectrometer or scintillation counter.
One of the limitations of this method is the possibility of false negative results when antibiotics are used to eradicate H. pylori. Precautions should be taken with diabetics and phenylketonurics. Some UBT products have age restrictions.
Serology – Historically, serologic tests assay for immunoglobulin G (IgG) antibodies to H. pylori by enzyme immunoassay (EIA) and have been the recommended tests for screening prior to H. pylori therapy. However, due to its high rate of false positives and false negatives, serology is no longer considered appropriate. Antibodies are present in serum for a very long time after eradication. Therefore, serology cannot be used to assess whether the H. pylori infection is an active infection or a past exposure, or if eradication has taken place.
Histology, rapid urease testing, and culture are based on endoscopy and biopsy. These techniques are reserved for patients who require endoscopy because of alarm symptoms or who have new symptoms that develop after the age of 55 years. For other patients who have ulcer-like dyspepsia or other gastrointestinal signs and symptoms that suggest H. pylori infection or PUD, initial non-invasive testing is appropriate.
ACG=American College of Gastroenterology
AGA=American Gastroenterological Association
References: 1. Chey WD, Wong BCY, and the Practice Parameters Committee of the American College of Gastroenterology. American College of Gastroenterology guideline on the management of Helicobacter pylori infection. Am J Gastroenterol. 2007;102:1808-1825. 2. Talley NJ, Vakil NB, Moayyedi P. American Gastroenterological Association medical position statement: evaluation of dyspepsia: Gastroenterology. 2005;129:1756-1780. 3. ImmunoCard STAT!® HpSA® HD Package Insert, rev. 09/14 4. Premier Platinum HpSA® Plus [package insert]. Cincinnati, OH: Meridian Bioscience, Inc. 5. BreathTek [package insert]. Rockville, MD: Otsuka America Pharmaceutical, Inc 6. BreathID [package insert]. Modin, Israel: Exalenz Bioscience Ltd.