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EPIC CODE: LAB259 Giardia Antigen, Feces

Additional Codes

Sunquest:  GIARDM
Mayo:         GIAR
Previously: ARUP 0060048

Reporting Name

Giardia Ag, F

Useful For

Sensitive screening for the detection of Giardia antigens present in fecal specimens

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type


Ordering Guidance

Duodenal, colonic wash, or small bowel aspirates are not acceptable for this test. If giardiasis is suspected, order OAP / Ova and Parasitic, Concentrate and Permanent Smear, Microscopy, Feces.

Specimen Required

Submit only 1 of the following specimens:



Specimen Type: Preserved feces


-Formalin 10% Buffered Neutral (T466)

-Stool Collection Kit, Random (T635)


Preferred: Fecal container with 10% buffered formalin preservative

Acceptable: SAF (sodium acetate formalin)

Specimen Volume: 5 g

Specimen Stability Information: Ambient (preferred) 60 days


Specimen Type: Unpreserved feces


-Stool container, Small (Random), 4 oz (T288)

-Stool Collection Kit, Random (T635)

Container/Tube: Fecal container

Specimen Volume: 5 g

Specimen Stability Information: Frozen 60 days

Specimen Minimum Volume

2 g

Specimen Stability Information

Specimen Type Temperature Time Special Container
Fecal Varies

Reference Values


Day(s) Performed

Monday through Saturday

Test Classification

This test has been cleared, approved, or is exempt by the US 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 duodenalis (also known as Giardia lamblia, Giardia intestinalis) is a flagellated protozoan parasite found in contaminated natural streams, lakes, and surface water municipal reservoirs. Several animals may serve as a host for G duodenalis, including dogs and beavers. Humans become infected when ingesting the environmentally resistant parasite cysts in water, food, and by the fecal-oral route (eg, on hands or fomites).


Following ingestion, each cyst releases two trophozoites, which infect the small intestine by attaching to the mucosa with a ventral sucking disc. Infection may be associated with a variety of outcomes ranging from asymptomatic disease (estimated to occur in 50% of infected individuals) to acute and chronic giardiasis. When present, symptoms generally appear 7 to 14 days after infection and consist of watery diarrhea, malaise, malodorous steatorrhea, flatulence, abdominal cramping, nausea or vomiting, weight loss, and low-grade fever. Less commonly, patients experience constipation and urticaria. Symptoms will resolve in most patients after a period of several weeks. However, approximately 15% to 20% will remain chronically infected without treatment and experience ongoing loose stools, weight loss, malabsorption, steatorrhea, abdominal cramping, flatulence, and burping. Longstanding malabsorption may result in vitamin deficiencies and hypoalbuminemia. Acquired lactose intolerance may also occur and persist for months after successful parasite eradication.


Giardiasis is the most common intestinal parasitic infection in the United States reported to the Centers for Disease Control and Prevention and is a common cause of diarrhea in children (especially in daycare centers), travelers, and campers or hikers. It is also responsible for waterborne epidemics. Although Giardia parasites (cysts and trophozoites) may be seen using the microscopy-based stool parasitic exam (OAP / Ova and Parasitic, Concentrate and Permanent Smear, Microscopy, Feces.), this is an insensitive method for detection and requires examination of three or more specimens. Instead, detection of parasite antigen or DNA is recommended for optimal sensitivity. The Giardia antigen test is ideal for settings in which giardiasis is specifically suspected (eg, outbreak scenarios), whereas the multiplex gastrointestinal polymerase chain reaction  panel (GIP / Gastrointestinal Pathogen Panel, PCR, Feces) is better suited for evaluating multiple potential causes of diarrhea, including parasitic, viral, and bacterial pathogens.


For more information about diagnostic tests that may be of value in evaluating patients with diarrhea see the following:


-Parasitic Investigation of Stool Specimens Algorithm

-Laboratory Testing for Infectious Causes of Diarrhea


A positive enzyme-linked immunosorbent assay indicates the presence in a fecal specimen of Giardia antigens.


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


Small numbers of organisms residing only in the duodenum may not yield a positive test result.


Giardia antigen detection should be used as an aid in diagnosis of giardiasis. A single diagnostic assay should not be used as the only criteria to form a clinical conclusion.


Testing of at least 2 consecutive fecal specimens by enzyme-linked immunosorbent assay is recommended before considering the results negative.


Feces containing large amounts of leukocytes or red blood cells may give false-positive results.

Clinical Reference

1. Garcia LS, Arrowood M, Kokoskin E, et al: Practical Guidance for Clinical Microbiology Laboratories: Laboratory Diagnosis of Parasites from the Gastrointestinal Tract. Clin Microbiol Rev. 2017 Nov 15;31(1):e00025-17

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 Feb;39(2):474-477

3. Centers for Disease Control and Prevention (CDC) National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Division of Foodborne, Waterborne, and Environmental Diseases (DFWED): Parasites-Giardia. CDC; Updated May 19, 2022. Accessed October 31, 2022. Available at

Method Description

Giardia antigens present in the stool supernatant are captured by antibodies coating the wells of a microtiter plate. The bound antigen is sandwiched by the addition of a second antibody, and the signal is amplified by adding biotin-streptavidin horseradish peroxidase. Blue color develops with the presence of bound antigen. The reaction is stopped with the addition of acid and read visually or with the aid of a spectrophotometer.(Rosenblatt JE, Sloan LM, Schneider SK: Evaluation of an enzyme-linked immunosorbent assay for the detection of Giardia lamblia in stool specimens. Diagn Microbiol Infect Dis. 1993 May-Jun;16:337-341; package insert: ProSpecT Giardia Microplate Assay. Oxoid; 03/2012)

Report Available

Same day/1 to 4 days

Specimen Retention Time

Fresh/Frozen: 1 week; Preserved specimens: 1 week

Reject Due To

Grossly bloody feces (containing no visible specimen)
Very mucoid feces
Specimens preserved in ECOFIX (green cap), C and S (orange cap), or methiolate formalin (MF)

NY State Approved


Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Secondary ID


Supportive Data

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