The determination of the affinity (avidity) of specific IgG antibodies against Toxoplasma is used to distinguish recent from past infection with the parasite in pregnant women in cases where specific IgM or IgA antibodies do not help determine the phase of the infection.
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Toxoplasmosis is a systemic, parasitic disease caused by the protozoan Toxoplasma gondii. It is transmitted to humans by consuming undercooked meat from infected animals or ingesting oocysts from handling cat litter containing contaminated feces. The parasite can also be transmitted to the fetus through the mother's placenta. After ingestion, the parasites travel to various body tissues and cluster together in large numbers to form oocysts.
Acquired toxoplasmosis is usually asymptomatic in patients with intact immune systems. In immunosuppressed cases, it can cause hyperpyrexia, lymphadenopathy, lymphocytosis, and, in some cases, encephalitis, pneumonitis, myocarditis, myositis, and possibly death. Congenital fetal toxoplasmosis can cause severe abnormalities, including blindness, hydrocephalus, and mental retardation, and can lead to intrauterine or postnatal death.
Serological testing for antibody titer to Toxoplasma gondii is recommended for all pregnant women. If the antibody titer is positive, indicating past infection, there is no risk to the fetus. However, the fetus is at risk if the disease occurs during pregnancy. Thus, if the antibody titer indicates active infection or is initially negative, the test should be repeated at every microbiological check-up in the first 5 months of pregnancy and shortly before delivery. When toxoplasmosis is acquired early in pregnancy, abortion may be recommended. Toxoplasmosis is common in patients with AIDS.
The determination of avidity is a diagnostic method used to differentiate recent (acute) from past infection with Toxoplasma gondii in a patient's serum. Avidity is defined as the binding strength of the antibody (in a serum sample) for the corresponding antigen. The low affinity of IgG antibodies in the early stage of infection can be differentiated from the high affinity of antibodies associated with past infection. Determining IgG antibody avidity is an additional analysis of the classic serological test concerning infection status with Toxoplasma gondii.
Important Note
Laboratory test results are the most critical parameter for diagnosing and monitoring all pathological conditions. Between 70 to 80% of diagnostic decisions are based on laboratory tests. Correctly interpreting laboratory results allows a doctor to distinguish "healthy" from "diseased."
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be analyzed based on each case and family history, clinical findings, and the results of other laboratory tests and information. Your physician should explain the importance of your test results.
At Diagnostiki Athinon, we answer any questions you may have about the test you perform in our laboratory and contact your doctor to ensure you receive the best possible medical care.
