Toxoplasmosis other diagnostic studies
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Other Diagnostic Studies
The diagnosis of toxoplasmosis cna be established by:
- Observation of parasites in patient specimens, such as bronchoalveolar lavage material from immunocompromised patients, or lymph node biopsy.
- Isolation of parasites from blood or other body fluids, by intraperitoneal inoculation into mice or tissue culture. The mice should be tested for the presence of Toxoplasma organisms in the peritoneal fluid 6 to 10 days post inoculation; if no organisms are found, serology can be performed on the animals 4 to 6 weeks post inoculation.
- Detection of parasite genetic material by PCR, especially in detecting congenital infections in utero.
- Serologic testing is the routine method of diagnosis, because the techniques described above are technically complex and generally not rewarding.
There is an algorithm for the immunodiagnosis of toxoplasmosis for individuals greater than one year of age.
- The IFA and EIA tests for IgG and IgM antibodies are the tests most commonly used today.
- Persons should be initially tested for the presence of Toxoplasma-specific IgG antibodies to determine their immune status.
- A positive IgG titer indicates infection with the organism at some time. If more precise knowledge of the time of infection is necessary, then an IgG positive person should have an IgM test performed by a procedure with minimal nonspecific reactions, such as IgM-capture EIA.
- A negative IgM test essentially excludes recent infection, but a positive IgM test is difficult to interpret because Toxoplasma-specific IgM antibodies may be detected by EIA for as long as 18 months after acute acquired infection.