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Test Name:
Toxoplasma Avidity Test
- SBMF No:
45197 - Performance Lab Name:
Toxoplasma Serology Laboratory, Palo Alto Medical Foundation - Test Mnemonic:
TOXO AVID - ABN:
Not required - CPT Code:
86777; 86777-59; 86778 - Test Includes:
Toxoplasma IgG Antibody, Dye Test
Toxoplasma IgG Antibody Avidity
Toxoplasma IgM Antibody, ELISA - Also See:
28137 Toxoplasma IgG & IgM Antibodies, Serum - Spec Type:
Serum - Spec Container:
Red top (serum) tube - Pref Vol:
1.0 mL - Min Vol:
0.5 mL - Fasting:
No - Spec Collect:
Do not use gel-barrier tubes for specimen collection
Routine venipuncture - Spec Process:
Clot 30 minutes
Promptly centrifuge 15 minutes
Immediately transfer serum to separate plastic tube - Spec Store Transport:
Refrigerated (2-8°C) preferred
Room temperature or frozen acceptable - Clinical Significance:
The functional affinity of specific IgG antibodies is initially low after primary antigenic challenge and increases during subsequent weeks and months. Protein-denaturing reagents including urea are used to dissociate the antibody-antigen complex. The avidity result is determined using the ratios of antibody titration curves of urea-treated and untreated serum.
The avidity test is an additional confirmatory diagnostic tool for those patients with a positive and/or equivocal IgM test. Health care providers and clinical laboratories involved in the care of pregnant women should be aware that avidity testing is a confirmatory test and not the ultimate test for decision-making. Its highest value is observed when laboratory test results reveal high IgG avidity antibodies and the serum is obtained during the time window of exclusion of acute infection for a particular method (i.e. 12 weeks for the Labsystems method, 16 weeks for the VIDAS-bioMérieux method). Low or equivocal IgG avidity antibody results should not be interpreted as diagnostic of recently acquired infection. These low or equivocal avidity antibodies can persist for months to one year or longer.
- Reference Range:
High avidity excludes infection within the previous 4 months - Day Run:
Mon, Wed - Time Reported:
Within 6 days - Test Type:
INFECTIOUS ANTIBODY
