Related tests: TORCH
TORCH complex
The term “TORCH complex” refers to a series of tests recommended for women when they are planning to have a baby or, at the latest, when they find out they are pregnant, because they help prevent infections that affect the embryo and foetus.
The letters of the TORCH complex stand for:
T for Toxoplasma (the parasite) or toxoplasmosis (the infection it causes)
O for Others, a group of tests that it is advisable to have before a pregnancy to avoid unpleasant consequences for the future baby (such as syphilis or the various forms of hepatitis; over the years more have been added, for example HIV/AIDS).
R for Rubella (the infection) or rubella test (the name of the test)
C for Cytomegalovirus (the name of the virus)
H for Herpes simplex (the name of the virus, which can be type 1 if the infection is on the lips or type 2 if it is sexually transmitted).
The tests in the TORCH complex check whether a person’s blood contains antibodies against a specific infection. There are two categories, and both must be tested:
IgG: if present, these antibodies indicate that the person has come into contact with that particular infection; they remain in the body for life, even after the person has recovered from the disease.
IgM: if present, these antibodies indicate not only that the person has caught the infection, but also that it is still under way, i.e. in the acute phase, or at least relatively recent (after recovery they gradually disappear). So if IgM antibodies are absent but IgG antibodies are present, the infection has been caught but is now over.
Why they are done
These tests are generally carried out on the advice of the gynaecologist before or at the start of a pregnancy (and also for monitoring during pregnancy) to rule out or keep under control the possibility that the baby could be born with problems caused by one of these infections. The tests check whether the woman has developed antibodies against each disease, because if she has, the infection has already been caught and she cannot catch it again (so it cannot be passed on to the baby). The exceptions are cytomegalovirus and herpes simplex virus, which always remain latent in the body and can reactivate when the body’s defences are weak; if there are no antibodies, the woman could still catch the disease. Individually, i.e. one by one, these tests can also be used to diagnose whether an infection is present when a person feels unwell and is suspected of having one of these diseases.
How they are done
These laboratory tests are carried out with a normal blood test, preferably on an empty stomach.
Results
NORMAL VALUES
Anti-Toxoplasma IgG antibodies 0-8 IU/ml
Anti-Toxoplasma IgM antibodies up to 0.200 absent
0.200-1.000 borderline
above 1.000 present
Anti-Toxoplasma antibody “avidity” absent
Anti-rubella IgG antibodies 0-10 IU/ml
Anti-rubella IgM antibodies up to 0.600 absent, 0.600-1.000 borderline, above 1.000 present
Anti-cytomegalovirus IgG antibodies 0-15 AU/ml
Anti-cytomegalovirus IgM antibodies 0-0.5 AU/ml
What they mean
Anti-Toxoplasma IgG antibodies: a result within the normal range indicates that the infection has never been caught.
• If the result is higher than the normal value, the person has caught the disease and may already have recovered or it may still be under way, so it is always advisable to test for IgM antibodies as well.
Anti-Toxoplasma IgM antibodies: a result within the normal range indicates that there is no current infection.
A result above this value, between 0.200 and 1.000, indicates that antibodies are probably present in the blood and therefore that there is probably a current or recent Toxoplasma infection (testing for anti-Toxoplasma antibody avidity will remove any doubt).
A result above 1.000, on the other hand, indicates the presence of anti-Toxoplasma antibodies and therefore a current infection (appropriate treatment must be given, especially if the woman is pregnant).
Anti-Toxoplasma antibody avidity: this is done when both IgG and IgM are high.
If the result is “absent” or “negative”, the infection is not in the acute phase.
If, on the other hand, the result is “present” or “positive”, the infection is under way.
Rubella IgG test: if the value is within the normal range, the person has no antibodies against rubella and, if she is a woman planning to have a baby, she is advised to be vaccinated to protect herself against the risk of catching the infection.
• If the result is higher than normal, the person has been exposed to the virus, but this does not show whether there is a
current infection (so it is always advisable to test for rubella IgM antibodies as well).
Rubella IgM test: a value below 0.600 is normal and indicates that there has been no recent rubella infection.
A value between 0.600 and 1.000 is borderline, so it is advisable to repeat the test 7-15 days later to see how the antibodies are changing.
A value above 1.000, on the other hand, indicates a recent infection.
Anti-cytomegalovirus IgG antibodies: a value between 0 and 15 IU (international units) per millilitre of blood indicates that there has been no infection with the virus.
• If the value is higher, the person has had the disease, but it is not known whether it is current or recent (so IgM antibodies must be tested).
Anti-cytomegalovirus IgM antibodies: a value between 0 and 0.5 IU (international units) per millilitre of blood indicates that there has been no recent infection with the virus.
• A higher value, on the other hand, indicates a recent infection. If a pregnant woman is about to give birth, the gynaecologist will recommend a cervical swab to check for the virus on the neck of the womb. If the infection is present on the mucosa, a caesarean section is preferable to a natural birth, so that the baby is not at risk of infection.
Anti-herpes simplex type 1 (lips) or type 2 (sexually transmitted) IgG antibodies: a result of “absent” or “negative” means that the person’s blood does not contain antibodies against this infectious agent and therefore that they have never had the disease. This means they could still catch it, and in pregnancy this poses a risk to the future baby.
If, on the other hand, the result is “present” or “positive”, the person has come into contact with the disease at some point in their life. To find out whether it is in the acute phase, it is always advisable to test for IgM antibodies as well.
Anti-herpes simplex type 1 (lips) or type 2 (sexually transmitted) IgM antibodies: a result of “absent” or “negative” means that the disease is not in the acute phase, and if IgG antibodies are “positive”, the person has come into contact with the virus in the past and it remains latent.
If, on the other hand, the result is “present” or “positive”, the disease is current or at least recent. For herpes simplex type 2, the same applies regarding the cervical swab (see cytomegalovirus).