What is being tested?

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:

• Toxoplasmosis is a parasitic infection that can be passed from mother to baby through the placenta during pregnancy. An infection with Toxoplasma gondii can cause eye or central nervous system infections. If acquired during the pregnancy, it may result in a miscarriage or cause birth defects. Toxoplasmosis may be acquired after ingesting the parasite through eating contaminated undercooked meat or contaminated raw fruit or vegetable, when handling the excrement of infected cats, or by drinking contaminated unpasteurised  milk.
• Rubella is a vaccine preventable disease caused by a virus, and is also known as German measles. If contracted early in the pregnancy the infant may develop hearing loss, vision problems, heart disease, liver or kidney disease, restricted growth, blood disorders, or pneumonia. Problems that may develop during childhood include autism, intellectual disability, immune disorders, diabetes, or thyroid disease.
• Cytomegalovirus (CMV) is a viral infection that the mother may acquire and pass to the fetus. Many adults have been infected with CMV at some point in their life and it usually causes a mild illness. It may pass to the fetus during the pregnancy, during the birth process, or infect newborns through breast milk. An infection acquired early in pregnancy may be associated with neurological problems for the baby such as seizures, hearing loss, eye disease or developmental delay.  An fetus infected late in pregnancy is more likely to have hepatitis, pneumonia or blood disorders. 
• Herpes simplex virus (HSV) is a common viral infection. The two most common infections with HSV are 'cold sores' affecting the lips and genital herpes. Both of these infections can recur. HSV is most commonly acquired through oral or genital contact. Newborns who contract the virus usually do so during travel through the birth canal of a woman who has a genital infection with HSV. The virus may spread throughout the newborn’s body, attacking vital organs. Treatment with specific antiviral medication should begin as soon as possible in the infected newborn. Even if treated, surviving babies may have permanent damage to the central nervous system.

How is it used?

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.

When is it requested?

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:

• exceptionally small size relative to the gestational age
• deafness
• seizures
• heart defects
• cataracts
• enlarged liver or spleen
• low platelet level 
• jaundice

What does the result mean?

Results are usually given as positive or negative, indicating the presence or absence of IgG antibodies for each of these infectious agents (toxoplasma, rubella, and  CMV. 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 at least 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.

Is there anything else I should know?

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 can be done earlier in the disease process and are more specific.

Common questions

• If I have a positive antibody test, does that mean I am infected?

A positive IgG antibody test is usually a sign of past exposure to the TORCH agent and is not a marker for current active infection. Detection of IgM antibody is more difficult, and false negative and false positive results may occur. Any positive results should be confirmed with additional specific tests before the diagnosis is considered valid. If your doctor suspects that you or your newborn may have one of these infections, even though the results were negative, other tests for the suspected infection should be done.

• What type of testing is used to confirm infection with these microorganisms?

To make the diagnosis of an active infection with one of the TORCH agents, more specific confirmatory tests may be required. In a baby, cerebrospinal fluid testing (requiring a lumbar puncture or “spinal tap”) is often used to confirm toxoplasmosis, herpes and rubella; urine may be tested for cytomegalovirus; and skin lesions may be scraped and tested for herpes simplex virus. Making the diagnosis of toxoplasmosis in the pregnant woman or the baby may require additional blood samples, which are sent to a reference lab that specialises in this testing.

Making the diagnosis while the mother is still pregnant may require tests such as amniocentesis which will be discussed with you and organised by your doctor.