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TORG
83304
TORCH Profile IgG
Clinical Information: Toxoplasma: 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 cysts.
Infection of the normal adult is commonly asymptomatic. In cases with clinical manifestations, the most
common symptom is lymphadenopathy, which 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. Rubella: Primary postnatal rubella infection
(German or 3-day measles) is typically a mild, self-limiting disease characterized by a maculopapular
rash, fever, malaise, and lymphadenopathy. Conversely, primary prenatal rubella infections may have
devastating results. In utero infections may severely damage the fetus, particularly if the infection occurs
during the first 4 months of gestation. Congenitally infected infants may exhibit 1 or more defects
including congenital heart disease and mental retardation. Prior to the introduction of the rubella vaccines,
approximately 15% of childhood sensorineural deafness and 2% of congenital heart defects were
attributed to congenital rubella infection in both the United States and the United Kingdom. During the
epidemic of 1962 to 1965, rubella infections during pregnancy were estimated to have caused 30,000
stillbirths and 20,000 malformed infants in the United States. The US rubella vaccination program, which
calls for vaccination of all children, has significantly reduced the incidence of rubella. Cytomegalovirus
(CMV): CMV is a significant cause of morbidity and mortality, especially in organ transplant recipients
and individuals with AIDS.(1,2) CMV is also responsible for congenital disease of the newborn.
Infections with CMV result from reactivation of latent virus from a previous infection, transmission of the
virus from a donor organ or blood product, or initial or primary contact with the virus in a seronegative
patient. Infection in immunologically normal patients can cause mononucleosis similar to that produced
by infection with Epstein-Barr virus (EBV). Infection in immunocompromised hosts commonly results in
more severe disease. Herpes Simplex Virus (HSV): The herpes virus family contains HSV types 1 and 2,
varicella-zoster virus, CMV, EBV, and human herpesvirus 6, 7, and 8 (Kaposi sarcoma). HSV types 1 and
2 produce infections that are expressed in various clinical manifestations, ranging from mild stomatitis to
disseminated and fatal disease. The more common clinical conditions include gingivostomatitis, keratitis,
encephalitis, vesicular skin eruptions, aseptic meningitis, neonatal herpes, genital tract infections, and
disseminated primary infection. Infections with HSV types 1 and 2 can differ significantly in their clinical
manifestations and severity. HSV type 2 is the cause of the majority of urogenital infections and is almost
exclusively found in adults. Type 1 HSV is associated closely with orolabial infection, although genital
infection with this virus can be common in some populations.
Useful For: Determination of rubella immune status in individuals >6 months of age As an indication
of past or recent infection with Toxoplasma gondii, cytomegalovirus, or herpes simplex virus in
individuals >6 months of age
Interpretation: Toxoplasma: 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
recent or previous infection and is present in up to 70% of the adult population in the United States. 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
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