Helicobacter pylori Antibody, IgA, Serum
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Helicobacter pylori is a spiral-shaped, gram-negative bacillus that has been associated with gastritis, gastric and duodenal ulcers, and gastric malignancies.
Helicobacter pylori is found worldwide. In Caucasian populations in the United States and other industrialized countries, Helicobacter pylori infection is infrequent in childhood. Prevalence increases 0.5% to 2% with each year of age, reaching about 50% in those who are 60 or older. Prevalence rates appear to be higher in African American and Hispanic populations as compared to rates among Caucasians; this is thought to be due to socioeconomic status. In a random population of 200 apparently healthy blood donors tested for Helicobacter pylori IgG antibody, the positivity rate was 27.5%.
The gold standard for diagnosis of Helicobacter pylori disease is gastric biopsy and evaluation for the presence of spirochetes by gram, silver, giemsa, or acridine orange stains. Alternatively, biopsied tissue can be examined by immunofluorescence or immunoperoxidase methods, rapid urease testing, and/or culture.
Exposure to Helicobacter pylori can be determined by detection of IgA, IgG, or IgM-class serum antibodies to the organism. Screening patients for the presence of antibodies to Helicobacter pylori is a convenient, noninvasive means for assessing whether a patient has been exposed to Helicobacter pylori and whether gastrointestinal symptoms may be related to Helicobacter pylori infection. Because serology may lack specificity and does not distinguish between recent or remote infection, active disease is best diagnosed by the Helicobacter pylori stool (HPSA / Helicobacter pylori Antigen, Feces) antigen assay or by the Helicobacter pylori urea breath test (UBT / Helicobacter pylori Breath Test).
See Helicobacter pylori Diagnostic Algorithm in Special Instructions.
Screening for Helicobacter pylori
Patients with Helicobacter pylori infection nearly always develop IgG class antibodies. However the presence of IgA-class antibodies does not distinguish between remote exposure to Helicobacter pylori and acute, ongoing infection. If clinically indicated, additional tests including either the urea breath test or the stool antigen assay should be performed to determine infection status.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This assay should be performed only on patients with gastrointestinal symptoms and should not be used to test asymptomatic patients.
A positive test result does not distinguish between colonization or infection by Helicobacter pylori and does not indicate the presence of gastrointestinal disease. It should be used as an aid to the detection of such disease with other clinical tests such as the urea breath test or stool antigen assay.
A negative result does not preclude the absence of antibodies to Helicobacter pylori. Colonization may be present, however it may be in its very early stages or the antibody titer may be too low for the assay to detect.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Negative (Results with index value of <18.00 are negative.)
Equivocal (Results with index values of > or =18.00 but < or =20.00 are equivocal.)
Positive (Results with index values of >20.00 are positive.)
Clinical References Provides recommendations for further in-depth reading of a clinical nature
Couturier MR: The Evolving Challenges of Helicobacter Pylori Disease, Diagnostics, and Treatment, Part 1. Clinical Microbiology Newsletter 2013;35(3):19-24