Specimen

Serum

Collection Medium:

Minimum:

2 mL red top tube (no additive)

Testing Schedule:

Test is performed twice weekly.

Analytic Time:

5 days

Reference Range:

Anti-T.gondii IgM   Anti-T.gondii IgG   Interpretation

Negative            Negative            No active or prior T. gondii
                                        infection.

Negative            Positive            Previous infection with
                                        T. gondii.   Reactivation
                                        status cannot be determined.

Negative            Equivocal           Obtain a new specimen for
                                        repeat IgG testing.

If patient has an equivocal or positive IgM result, a new specimen will 
be requested and sent to a reference laboratory for further testing.  
The patient may or may not be acutely infected with T. gondii.

Comments:

This test is a semiquantitative enzyme-linked fluorescent immunoassay 
(ELFA) for detection of anti-Toxoplasma  gondii IgG to aid in 
determining immune status.  A qualitiative ELFA for presumptive 
detection of anti-Toxoplasma gondii IgM to aid in the diagnosis of 
acute, recent, or reactivated T. gondii infection is also performed.

T. gondii is a parasite that infects many humans, but uncommonly causes 
disease (toxoplasmosis).  The seroprevalence of anti-T. gondii IgG 
antibodies varies within the U.S.  In immunocompetent individuals, 
toxoplasmosis infection is usually subclinical.  Women who become 
infected during pregnancy are at risk for transmitting the infection to 
the fetus.  Primary or reactivation of T. gondii infection in 
immunocompromised patients can be life-threatening.

Test
Limitations:

Positive results for the IgM assay are presumptive. Further testing 
must be performed to determine the presence or absence of IgM 
antibodies.

Negative test results may occur early in the course of infection.

During reactivation, an IgM response may not occur, or be present at 
levels to low to be detected.

Positive results from cord blood are usually the result of passive 
transfer of antibodies from the mother to the fetus.

Interpret positive results with caution if patients have received blood 
products within the past three months.

In an immunocompromised patient, a negative result may not rule out 
infection, because of a diminished immune response.

References:

Berrebi A, Kobuch WE. Toxoplasmosis in pregnancy. The Lancet 344:950, 
1994.

Thulliez P, Daffos F, Forestier F. Diagnosis of toxoplasma infection in 
the pregnant woman and the unborn child, current problems. Scand J 
Infect Dis 84:18-22, 1992.

Zufferey J et al. Prevalence of latent toxoplasmosis and serological 
diagnosis of active infection in HIV-positive patients. Eur J Clin 
Microbiol Infect Dis 12:591-595, 1993.

Methodology:

Enzyme-Linked Fluorescent Immunoassay (ELFA)

CPT Code:

86778

See also:
Toxoplasmosis Antibody, IgG, Serum

See Additional Information:
Microbiology Specimen Collection and Transport