Sorted By Test Name - Mayo Medical Laboratories

TOXOG
8267
amniotic fluid specimens (PTOX/81795 Toxoplasma gondii, Molecular Detection, PCR). For
confirmation of a diagnosis, the FDA issued a Public Health Advisory (7/25/1997) suggesting that sera
found to be positive/equivocal for Toxoplasma gondii IgM antibody be sent to a Toxoplasma reference
laboratory. CDC or Jack Remington, M.D., Palo Alto Medical Foundation, 860 Bryant Street, Palo Alto,
CA 94301, were recommended. (Reviewed 12/2011)
Reference Values:
Toxoplasma ANTIBODY, IgG
or =8 IU/mL (positive)
Toxoplasma ANTIBODY, IgM
Test value threshold or =0.55- or =0.65 is positive
Clinical References: 1. Luft BJ, Remington JS: Toxoplasmic encephalitis in AIDS. Clin Infect Dis
1992 August;15(2):211-222 2. Wong SY, Remington JS: Toxoplasmosis in pregnancy. Clin Infect Dis
1994 June;18(6):853-862
Toxoplasma Antibody, IgG, Serum
Clinical Information: Toxoplasma gondii is an obligate intracellular parasite that is capable of
infecting a variety of intermediate hosts including humans. Infected definitive hosts (cats) shed oocysts in
feces that rapidly mature in soil and become infectious. Toxoplasmosis is acquired by humans via
ingestion of food or water contaminated with cat feces or undercooked meats containing oocysts.
Infection of the normal adult is commonly asymptomatic. In cases with clinical manifestations, the most
common symptom is lymphadenopathy that may be accompanied by an array of other symptoms making
differential diagnosis difficult. Severe-to-fatal infections do occur in adults immunocompromised by
cancer chemotherapy or other immunosuppressive treatment and in patients with AIDS. These infections
are thought to be caused by reactivation of latent infections and often involve the central nervous system.
Transplacental transmission of the parasites resulting in congenital toxoplasmosis can occur during the
acute phase of acquired maternal infection. The risk of fetal infection is a function of the time at which
acute maternal infection occurs during gestation. The incidence of congenital toxoplasmosis increases as
pregnancy progresses; conversely, the severity of congenital toxoplasmosis is greatest when maternal
infection is acquired early during pregnancy. A majority of infants infected in utero are asymptomatic at
birth, particularly if maternal infection occurs during the third trimester, with sequelae appearing later in
life. Congenital toxoplasmosis results in severe generalized or neurologic disease in about 20% to 30% of
the infants infected in utero; approximately 10% exhibit ocular involvement only and the remainder are
asymptomatic at birth. Subclinical infection may result in premature delivery and subsequent neurologic,
intellectual, and audiologic defects.
Useful For: Indication of past or recent infection with Toxoplasma gondii
Interpretation: Diagnosis of acute central nervous system, intrauterine, or congenital toxoplasmosis is
difficult by routine serological methods. A single positive IgG result is only indicative of exposure to
toxoplasma at some point in time (past or recent) and is present in up to 70% of the adult United States
population. The absence of IgG is helpful in that it usually indicates the absence of infection. However, a
negative result could mean either no previous exposure or could also be seen in cases of remote exposure
with subsequent loss of detectable antibody. Seroconversion from negative to positive IgG is indicative of
recent Toxoplasma gondii infection. Seroconversion indicates infection subsequent to the first negative
specimen. Specimens interpreted as equivocal may contain very low levels of IgG. A second specimen
should be drawn and tested.
Reference Values: