Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1367 page)

   Use

   Testing is requested for evaluation of patients with dyspepsia or other upper GI symptoms suggesting
H
.
pylori
infection. Stool specimens, collected and transported using standard laboratory methods. Testing may be submitted to monitor effect of treatment for
H
.
pylori
infection. Stool antigen become undetectable with effective therapy.

   Interpretation

   
Expected result:
Negative.

   
Positive result:
Active
H
.
pylori
infection. False-positive results may be seen in approximately 5% of tests.

   
Negative result:
The patient is unlikely to have active infection with
H
.
pylori
. False-negative results may be seen in 5–7% of patients; repeat testing or testing with other types of assays for infection should be considered in patients with high suspicion for
H
.
pylori
infection.

Suggested Reading

Choi J, Kim CH, Kim D, et al. Prospective evaluation of a new stool antigen test for the detection of
Helicobacter pylori
, in comparison with histology, rapid urease test,
¹³
C-urea breath test, and serology.
J Gastroenterol Hepatol.
2011;26:1053–1059.

HEPATITIS A VIRUS (HAV) ANTIBODIES (IgM AND TOTAL)

   Definition

   The detection of HAV-specific antibodies, both IgG and IgM, occurs early in the acute infection, with IgG persisting for years. Diagnosis of HAV infection requires positivity for IgM. HAV never causes chronic infection, but acute relapses occasionally occur.

   
Normal range:
Negative.

   Use

   Indicated, in conjunction with other serologic and clinical information, as an aid in the clinical laboratory diagnosis of individuals with acute or past hepatitis A virus infection aids in the identification of HAV-susceptible individuals prior to HAV vaccination.

   Limitations