To test for several infectious diseases that can cause birth defects in newborns and illness in adults.
If you are exposed to certain infectious diseases, if you become ill while pregnant or if a baby is born with congenital abnormalities that may be caused by an infection with one of these organisms.
A blood sample is drawn from a vein in the arm by needle or by heelprick for infants.
TORCH is an acronym for a group of four infectious diseases that may cause illness in pregnant women and may cause birth defects in their newborns depending on the stage of pregnancy when the mother is infected. The test is a screen for the presence of any of the antibodies to these infections. Confirmation of an active infection may require more specific tests.
The following tests make up the TORCH panel:
A blood sample is required for the test. Blood can be collected by a heelprick from an infant or a needle is used to draw blood from a vein in the arm.
Blood may be tested from either the mother or the newborn infant to determine if the illness observed in the newborn is caused by one of these infections. A blood test can determine if the person has had a recent infection, a past infection, or has never been exposed to the organism. Patients with recent infection with one of the TORCH agents will have IgM antibody to the specific agent, and those with a past infection will have an IgG antibody and no IgM antibody, and the IgG should remain for life. If neither immunoglobulin is detectable, it is likely there has been no infection with these microorganisms. Sometimes, if the infection is too recent to detect an antibody response, your doctor may ask you to repeat the test to look again for these antibodies.
The test is ordered if a pregnant woman is suspected of having any of the TORCH infections. Rubella infection during the first 16 weeks of pregnancy presents major risks for the unborn baby. If a pregnant woman has a rash and other symptoms of rubella, laboratory tests are required to confirm the diagnosis. A physician cannot tell if a person has rubella by their clinical appearance since many other infections may look the same. Women infected with toxoplasma or CMV may have flu-like symptoms that are not easily differentiated from other illnesses. Antibody testing will help the physician diagnose an infection that may be harmful to the unborn baby.
The test may be ordered on the newborn if the infant shows any signs suggestive of these infections, such as:
Results are usually given as positive or negative, indicating the presence or absence of IgG and IgM antibodies for each of these infectious agents (toxoplasma, rubella, CMV, and HSV). Presence of IgM antibodies in the mother can suggest a recent infection with that organism. IgM antibodies produced in the mother cannot cross the placenta so presence of this type of antibody in the infant strongly suggests an active infection. Presence of IgG and absence of IgM antibody in the infant may reflect passive transfer of maternal antibody to the baby and may not indicate active infection in the baby.
Likewise, the presence of IgM antibody in the pregnant woman suggests a recent infection or reactivation of the virus or parasite. Further testing must be done to confirm these results since IgM antibody may be present and persist for other reasons. IgG antibody in the pregnant woman may be a sign of past infection with one of these infectious agents. By testing a second blood sample drawn two weeks later, the level of antibody can be compared. If the second blood draw shows an increase in IgG antibody, it strongly suggests a recent infection with the infectious agent.
Use of the TORCH panel to diagnose these infections is becoming less common since more specific and sensitive tests to detect infection are available. Relying on the presence of antibodies may delay the diagnosis since it takes days to weeks for the antibodies to be produced. Detection of the antigen, detection of nucleic acids or growing the microorganism in culture can be done earlier in the disease process and are more specific.
Rubella, herpes, CMV, toxoplasmosis
Conditions: Pregnancy, Genital herpes
Familydoctor.org: Neonatal infections (USA)
Last Review Date: October 6, 2015