Test Catalog

Test ID: RCHAG    
Trypanosoma cruzi IgG Antibody, Lateral Flow Assay, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosis of chronic Trypanosoma cruzi infection (Chagas disease) via lateral flow assay

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Only orderable as a reflex. For more information see CHAG / Trypanosoma cruzi IgG Antibody, ELISA, Serum.

 

If ELISA result is positive or equivocal, then this test is performed at an additional charge.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Chagas disease (American trypanosomiasis) is an acute and chronic infection caused by the protozoan hemoflagellate, Trypanosoma cruzi is endemic in many areas of South and Central America. The parasite is usually transmitted by the bite of reduviid (or "kissing") bugs of the genus Triatoma, but may also be transmitted by blood transfusion, organ transplantation, vertically from mother to fetus, and also by food ingestion. The acute febrile infection is most often undiagnosed and often resolves spontaneously. Diagnosis of acute T cruzi infection is most frequently confirmed by microscopic identification of trypomastigotes in fresh preparations of anticoagulated blood or buffy coat. Parasitemia decreases and is undetectable within 90 days of infection.

 

Chronic T cruzi infections are often asymptomatic but may progress to produce disabling and life-threatening cardiac (cardiomegaly, conduction defects) and gastrointestinal (megaesophagus and megacolon) disease. These damaged tissues contain the intracellular amastigote of T cruzi. The parasite is not seen in the blood during the chronic phase. Diagnosis of chronic T cruzi infection relies on serologic detection of antibodies to this organism. However, no single serologic assay is sensitive and specific enough to be relied upon alone. Therefore, per current guidelines and the CDC, serologic confirmation of chronic T cruzi infection requires positivity on 2 tests utilizing 2 different methodologies or 2 different T cruzi antigen preparations. When results are discordant, a testing by a third assay is recommended to resolve the initial results or, alternatively, repeat testing on a new sample may be required.

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.

Only orderable as a reflex. For more information see CHAG / Trypanosoma cruzi IgG Antibody ELISA, Serum.

 

Negative

Interpretation Provides information to assist in interpretation of the test results

Positive:

Antibodies to Trypanosoma cruzi detected suggesting chronic T cruzi infection. Diagnosis of chronic T cruzi infection relies on the presence of appropriate exposure history and positive results by 2 distinct serologic assays. This patient was positive by both an anti-T cruzi IgG ELISA using purified, extracted T cruzi antigens and a lateral flow assay using recombinant T cruzi antigens.(1)

 

Negative:

No antibodies to T cruzi detected. Chronic T cruzi infection cannot be confirmed due to the discordant serologic results. Further testing (offered through the CDC) or repeat testing on a new sample is recommended.(1)

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

False-positive results may occur in patients infected with Leishmania species or other Trypanosoma species, including Trypanosoma rangeli. Additionally, false-positive results with the T cruzi lateral flow assay have been detected in patients with hepatitis C, toxoplasmosis, or syphilis.

 

A diagnosis of chronic Chagas disease requires both clinical evaluation (including exposure history) and laboratory results. Chagas disease should not be diagnosed based on a single serologic result alone.

 

A single negative result does not exclude the diagnosis of Chagas disease as antibodies to the pathogen may not yet detectable. Sensitivity of the assay may also be decreased in significantly immunosuppressed patients.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Bern C, Montgomery SP, Herwaldt BL, et al: Evaluation and treatment of Chagas disease in the United States: A Systematic Review 2007;298(18):2171-2181