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Test Code GIAR Giardia Antigen, Feces

Reporting Name

Giardia Ag, F

Useful For

Sensitive screening for the detection of Giardia lamblia antigens present in stool specimens

Testing Algorithm

The following algorithms are available in Special Instructions:

-Parasitic Investigation of Stool Specimens Algorithm

-Laboratory Testing for Infectious Causes of Diarrhea

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type


Advisory Information

Duodenal and small bowel aspirates are not acceptable for this test. If sprue is suspected, order test OAP / Parasitic Examination.

Specimen Required

Submit only 1 of the following specimens:


Preferred Specimen Type: Preserved stool

Supplies: Formalin - Meridian 10% Buffered Neutral (T466) or Stool Collection Kit, Random (T635)


Preferred: Stool container with 10% buffered formalin preservative (T466)

Acceptable: SAF (sodium acetate formalin)

Specimen Volume: 5 g

Specimen Stability Information: Ambient (preferred)/Refrigerated


Acceptable Specimen Type: Unpreserved stool

Supplies: Stool container, Small (Random), 4 oz (T288) or Stool Collection Kit, Random (T635)

Container/Tube: Stool container (T288)

Specimen Volume: 5 g

Specimen Stability Information: Frozen

Specimen Minimum Volume

2 g

Specimen Stability Information

Specimen Type Temperature Time
Fecal Varies

Reference Values


Day(s) and Time(s) Performed

Monday through Saturday, Varies

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
GIAR Giardia Ag, F 6412-1


Result ID Test Result Name Result LOINC Value
24085 Giardia Ag, F 6412-1

Clinical Information

Giardia lamblia (also known as G duodenalis, G intestinalis) are flagellated protozoa that can be found in contaminated natural streams, lakes, and surface water municipal reservoirs. Humans become infected when ingesting the environmentally resistant cysts in water, food, and by the fecal-oral route.


G lamblia primarily infects the small intestine causing malodorous watery diarrhea and flatulence after attaching by their ventral sucker. Malabsorption and lactose intolerance may also occur.


Giardiasis is the most common intestinal parasitic infection in the United States that is reported to the CDC and is a common cause of diarrhea in children (especially in day care centers), travelers, and campers. It is also responsible for waterborne epidemics. Although G lamblia may be detected using the microscopy-based stool parasitic exam (OAP / Parasitic Examination), up to 7 specimens may be necessary for optimal sensitivity. Instead, this test detects antigen using an enzyme-linked immunosorbent assay (ELISA), which is a more sensitive method for detection and is, therefore, a preferred method for detection.


See Parasitic Investigation of Stool Specimens Algorithm and Laboratory Testing for Infectious Causes of Diarrhea in Special Instructions for other diagnostic tests that may be of value in evaluating patients with diarrhea.


A positive enzyme-linked immunosorbent assay (ELISA) indicates the presence in a stool specimen of Giardia lamblia antigens.


As per the manufacturer, the assay has a sensitivity of 96%, specificity of 97%, and a positive predictive value of 95%.


Interpretation of results should be correlated with patient symptoms and clinical picture.

Clinical Reference

1. Janoff EN, Craft JC, Pickering LK, et al: Diagnosis of Giardia lamblia infections by detection of parasite-specific antigens. J Clin Microbiol 1989;27:431-435

2. Hanson KL, Cartwright CP. Use of an enzyme immunoassay does not eliminate the need to analyze multiple stool specimens for sensitive detection of Giardia lamblia. J Clin Microbiol 2001;39(2):474-477

Analytic Time

Same day/1 day

Reject Due To








Grossly bloody stool (containing no visible stool), or very mucoid stool


Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Secondary ID