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Test Code TXPG Toxoplasma gondii Antibody, IgG, Serum


Ordering Guidance


IgG antibodies in patients younger than 6 months of age are typically the result of passive transfer from the mother. To assess possible Toxoplasma gondii infection in patients younger than 6 months, order TXPM / Toxoplasma gondii Antibody, IgM, Serum.



Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.6 mL

Collection Instructions: Centrifuge and aliquot serum into plastic vial


Secondary ID

621838

Useful For

Quantitative detection of IgG antibodies to Toxoplasma gondii.

 

This test is not useful for diagnosing infection in infants younger than 6 months of age. In that age group, IgG antibodies usually are the result of passive transfer from the mother.

Method Name

Electrochemiluminescence Immunoassay (ECLIA)

Specimen Type

Serum

Specimen Minimum Volume

0.6 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 21 days
  Frozen  90 days
  Ambient  72 hours

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
Additives (eg, biocides, antioxidants) Reject

Reference Values

Negative

<1 IU/mL Negative

≥1-<3 IU/mL Borderline

≥3 IU/mL Positive

Reference values apply to all ages.

Interpretation

Negative:

Toxoplasma gondii IgG not detected. False-negative results may occur in immunocompromised patients or if testing was performed within 1 to 2 weeks of initial exposure. Repeat testing may be helpful. A single negative result should not be used to rule out toxoplasmosis, and repeat testing is recommended for patients at high risk for infection.

 

Borderline

Repeat testing on a new sample collected in 2-3 weeks is recommended to assess for seroconversion. Borderline Toxoplasma IgG results may be due to very low levels of circulating IgG during the acute stage of infection. Seroconversion from negative to positive IgG is indicative of T gondii infection after the first negative specimen.

 

Positive

Toxoplasma gondii IgG antibodies detected, indicating recent or past infection. A significant change in T. gondii IgG levels suggests recent infection. For confirmation of toxoplasmosis, the US Food and Drug Administration issued a Public Health Advisory (07/25/1997) that recommends sera found to be positive for T gondii IgM antibodies should be sent to a Toxoplasma reference laboratory.

Method Description

The electrochemiluminescence immunoassay for the in vitro quantitative determination of IgG antibodies to Toxoplasma gondii in human serum is a sandwich test principle. During the first incubation, 6 mcL of sample a biotinylated recombinant T. gondii-specific antigen labeled with a ruthenium complex form a sandwich complex. In the second incubation, streptavidin-coated microparticles are added and the complex becomes bound to the solid phase via interaction of biotin and streptavidin. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell II M. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier. Results are determined by a calibration curve which is instrument-specifically generated by 2-point calibration and a master curve provided via the cobas link.(Package insert: Elecsys Toxo IgG, Roche Diagnostics GmbH, 02/2022)

Day(s) Performed

Monday through Saturday

Report Available

Same day/1 to 3 days

Specimen Retention Time

14 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

86777

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TXPG Toxoplasma Ab, IgG, S 8039-0

 

Result ID Test Result Name Result LOINC Value
GTXP Toxoplasma Ab, IgG, S 40677-7
DEX04 Toxoplasma IgG Value 8039-0