Generality
Anti-transglutaminase (tTG) antibodies are IgA / IgG type immunoglobulins found in people with celiac disease.
Together with anti-endomysial antibodies (EMA), the tTg represent the most specific serological marker for the diagnosis of celiac disease.
Anti-transglutaminase antibodies are directed against a tissue protein (called transglutaminase antigen), located in the mucosa of the small intestine; this protein interacts with gliadin, playing a fundamental role in the pathogenesis of celiac disease.
CELIAC DISEASE is an autoimmune disease triggered, in genetically predisposed persons, by the ingestion of gluten (protein contained in wheat and other cereals). This results in malabsorption and morphological alterations of the intestinal mucosa (atrophy of the villi, hypertrophy of the crypts, thinning of the intestinal wall and infiltration of the mucosa by inflammatory cells).
In the organism affected by celiac disease there is also an altered immune system response, which causes the formation of auto-antibodies against gluten (called anti-gliadin antibodies) and against the intestinal mucosa (EMA or tTG).
Celiac disease therapy is a gluten-free diet. Failure to adhere to this diet is the main cause of persistent or recurrent symptoms.
What's this
Biological role and types of transglutaminase?
Transglutaminases are a group of enzymes involved in particularly important biological reactions.
Currently the existence of at least 8 different types of transglutaminases (TGs) has been recognized:
- plasma transglutaminase (coagulation factor XII);
- tissue translutaminase (liver, erythrocyte or endothelium);
- keratinocytic transglutaminase;
- epidermal transglutaminase;
- prostatic transglutaminase;
- transglutaminase X and others.
Transglutaminase and diagnosis of celiac disease
Tissue transglutaminase (tTG or TG2) is known to be the specific autoantigen of celiac disease.
The search for IgA antibodies against tissue transglutaminases is one of the most recent and widespread tests for the diagnosis of celiac disease (it supports or replaces the traditional search for anti-endomysial antibodies - EMA - and anti-gliadin - AGA). The exam uses an operator-independent and inexpensive immunoenzymatic technique, with sensitivity * and specificity ** close to 100% (respectively of 94 and 98% according to a study published in the European journal gastroenterology hepatology in 2005).
* ability to correctly identify the sick
** ability to correctly identify healthy people.
Why do you measure
The dosage of anti-transglutaminase antibodies is useful for a first gluten intolerance screening. The dosed antibody class is mainly IgA. In case of deficiency of these, the IgG class tTG antibodies are assayed.
The search for anti-transglutaminase (tTG) antibodies is also used in the monitoring of celiac patients on a gluten-free diet.
The dosage of tTG is indicated by the doctor in the presence of symptoms such as:
- Unexplained chronic diarrhea, with or without malabsorption;
- Flatulence;
- Abdominal pain and / or swelling;
- Iron deficiency anemia;
- Folate deficiency;
- Weight loss;
- Fatigue and fatigue;
- Depression and other mood disorders;
- Joint and bone pain.
In children, in the case of celiac disease, other symptoms may occur, including:
- Growth delay;
- Excessive and recurrent irritability;
- I made the color too light.
Normal values
Normally, anti-transglutaminase antibodies must be absent (ie the search yields a negative outcome).
Normal values:
- Negative tTG search <7 U / ml;
- Doubtful tTG research 7-10 U / ml;
- Positive tTG research> 10 U / ml.
Note : the reference interval of the exam can change according to age, sex and instrumentation used in the analysis laboratory. For this reason, it is preferable to consult the ranges listed directly on the report. It should also be remembered that the results of the analyzes must be assessed as a whole by the general practitioner who knows the patient's medical history.
Antibodies High - Causes
When the values of anti-transglutaminase antibodies are high, it is likely that the person is suffering from celiac disease. In general, the greater the presence of these antibodies, the more severe the gluten intolerance.
Low antibodies - Causes
If the presence of anti-transglutaminase antibodies is not found in the blood, it means that the patient is not affected by celiac disease. Low levels of tTG are not usually associated with medical problems and / or pathological consequences.
How to measure it
The search for anti-transglutaminase (tTG) antibodies is carried out through a simple blood sample.
Preparation
The dosage of anti-transglutaminase antibodies is a laboratory analysis that does not require any specific preparation. The doctor can indicate if it is necessary to observe a fast of at least 8 hours, during which a modest amount of water can be taken.
Interpretation of Results
The patient subjected to the tTG antibody dosage does not suffer from celiac disease if the test is "negative" or "absent", while the disease is present if it is "positive" or "present". This analysis is more sensitive and specific than the search for anti-endomysial antibodies (EMA).
During therapy (gluten-free diet) the test tends to become negative, so it is useful in monitoring the disease.
Reliability of the test
The risk of false positives (subjects that from the results of the examination appear to be celiac when in reality they are not), is superior for patients with Crohn's disease, ulcerative colitis, systemic lupus erythematosus or other inflammatory diseases, allergies, and chronic liver diseases.
If the antibody test produces positive results, an intestinal biopsy is still necessary for the diagnostic confirmation of celiac disease. During this examination the doctor gently drops a thin tube, introduced orally, to the first tracts of the small intestine, and using a microdevice mounted at the end, takes a piece of mucosa, subsequently analyzed in the laboratory.
