Lecture 3: Coeliac

Question 1

How does a leaky barrier lead to inflammation

Answer 1

Diagram on lecture

Intact:
ID involving T cell responses to autoantigens – if there are no autoantigens, T cells do not get the signal to activate and thus die by apoptosis

However, in the case of a leaky lamina propria, antigens may pass through where innate immune cells can recognise it and activate T cells and thus become activated, secreating various cytokines (TNF alpha and IFN gamma) inducing inflammation

Question 2

Causes of inflammation

Answer 2

1.Diet
poorly digested foods causes..
Swelling develops in the internal organs
autoimmune system views the inflammation as a toxin or a disease
It attacks the organ to stop the inflammation
makes the swelling worse

2.Lack of good bacteria in the GI Tract
A healthy balance of good bugs within your digestive tract keeps your bowel movements regular and helps you healthy.

if good bacteria are eliminated from your body…
Your immune system will then send agents to fight the bad bacteria
which can leave you feeling sick

Question 3

IBD types and symptoms

DWARF

Answer 3

Types of IBD
Ulcerative colitis
Crohn’s

Characterised by diarrhea, rectal bleeding, abdominal pain, fatigue and weight loss

• UC causes pseudopolyps (regenerating intestine cells)

Question 4

Draw the difference and describe difference between crohns and ulcerative colitis

Answer 4

UC – affects the colon ( distal progressing to the proximal colon) (large bowel or intestine)

Crohn’s – any part of the intestine from mouth to anus (Has skip lesiosn and located typically in the distal ileum and caecum).

Question 5

Causes of IBD

Answer 5

AID

Genetic factors
Human gene NOD2

Genetic:
Cytokines
Handling of bacteria
Antimicrobial peptide

Environment:
Toxins
Smoking
Antibiotics
Diet
Infections
Microorganisms

Question 6

Testing for IBD

Answer 6

1. FBC (particularly WBC)
   Can’t provide a definite diagnosis of IBD it can provide clues that you may be suffering from IBD.
   If your FBC shows a higher white blood cell count and/or an increase in the number of platelets (which help to stop bleeding by forming blood clots) this can indicate that you have inflammation - and inflammation can be a sign of IBD.
   A FBC test can also detect anaemia by measuringred blood cells. People with IBD can be at risk of anaemia.
2. Serology Markers of inflammation: pANCA, ASCA, CBir1, OmpC
   These are tests that look at serum and other bodily fluids and the proteins that are found within. In recent years various antibodies have been identified as being associated with IBD. Has the potential to look at autoantibodies that might lead to IBD. It can help to determine if you have IBD and, if so, which type of IBD you may have and its severity. Markers tested for include pANCA (antineutrophil cytoplasmic antibodies), ASCA (Saccharomyces cerevisiae antibodies), anti-CBir1 (common antigen), and OmpC (outer membrane protein C).
   But, these markers are not always present in all people with IBD
3. Ferritin and transferrin
   Ferritin is a protein which can be measured to indicate inflammation. It also stores iron and a low level of ferritin can be a good way of showing if you have low levels of iron in your blood. Anaemia is often caused by a lack of iron and people with IBD often suffer from anaemia. Transferrin is another protein which binds to iron. A test can be done to show how much iron is actually being carried by transferrin and if it is low this, again, can indication an iron deficiency.
4. Urea and electrolytes: measure urea and electrolytes potentially lost by diarrhoea and thus dehydration

People who are suffering with acute diarrhoea can often become dehydrated
A U&E test will measure the levels of electrolytes and given an indication of dehydration. It will also measure the levels of urea and it may also be requested to measure the levels of creatinine in your blood. A U&E test measures how well your kidneys are functioning.

Question 7

IBD treatment options

Answer 7

Main aim is to stop inflammation and prevent flare ups

Medication (eg coristeroids, biologics)

Special diets (crohns eat more pasta, potatoes, fish, steamed vegetables etc)

surgery (remove parts of colon (UC and crohns)

*very similar to CTD treatment

Question 8

What is coeliac disease

Answer 8

An immune reaction to eating gluten

Over time, the immune reaction to eating gluten creates inflammation that damages the small intestine’s lining,
leading to medical complications
prevents absorption of some nutrients (malabsorption)

Question 9

Symptoms and treatment for coeliac disease

Answer 9

The classic symptom is diarrhoea, bloating, wind, fatigue, low blood count (anaemia) and osteoporosis.

Treatment is a strict gluten-free diet
helps manage symptoms and promote intestinal healing

Question 10

Process of inflammation in coeliac disease

DRAW diagram and explain

Answer 10

Celiac disease is caused by an abnormal immune response to gluten peptides in the upper small intestine.

When gluten reaches the small intestine, it breaks down into gliadin. In celiac disease, gliadin is able to pass through the leaky junctions in the epithelial barrier in the small intestine and reach the underlying lamina propria. Once gliadin reaches the lamina propria, it binds to tissue transglutaminase and this deamidates (amide group is removed from an amino acid) it. Deamidated gliadin then reacts with antigen-presenting immune cells of the HLA-DQ2 or HLA-DQ8 subtype. Antigen-presenting cells stimulate T-cell and B-cell responses that promote cytokine release, antibody production, and lymphocyte infiltration. Antibodies made include:
Gliadin antibodies
Endomysial antibodies
tissue transglutaminase antibodies

These inflammatory processes lead to villous atrophy and crypt hyperplasia in epithelial cells (cilia shrinks)

Question 11

Cause of Coeliac disease and general inflam process

Effects?

Answer 11

an abnormal reactionby your immune systemto the protein gluten
Immune system mistakes gluten as a threat to the body; producing autoantibodies

these antibodies cause inflammation and flattening of tiny, finger-like projections called villi, which line the inside of your small bowel

The villi are responsible for absorbing nutrients and minerals from food.
can lead to nutritional deficiencies (low levels) of iron, folic acid andcalcium.

Question 12

3 main tests for coeliac disease and explanation

Answer 12

1.Blood tests; tTG A and looking at total IgA

tTG-IgA is an enzyme that helps with repairing of tissue damage, auto-antibodies, particularly IgA against tTG can be an indication of coeliacs disease. Tissue transglutaminase is an endomysial enzyme that is released in response to cellular stress.

Biopsy – gold standard
This involves a gastroscopy procedure in which several tiny samples (biopsies) of the small bowel are taken.because between 30% and 50% of the population who willneverdevelop the disease also have this gene.

Gene test
Coeliac disease is associated with genetic markers known as HLA DQ2 and HLA DQ8, which can be tested for with a simple blood test. This can be a very helpful test to do when the diagnosis is uncertain, because a negative test more-or-less rules out coeliac disease. This is because more than 95% (and perhaps as many as 99%) of people with coeliac disease will have one or the other of these markers. However, a positive HLA test isnotenough to confirm that a person has coeliac disease

Question 13

List the other coeliac tests

Answer 13

Tissue transglutaminase IgA and IgG

Gliadin antibodies

Deaminated Gliadin Peptide (IgG)

Endomysial antibodies (EMA)

Question 14

Anti-tTg (tissue transglutaminase) test description role of tTG
enzyme released by?
correlation of titres to state of inflam

Answer 14

ELISA

tTG are enzymes that catalyze the transfer of protein-bound glutamine residues to primary amines

tTG deamidates glutamine residues creating epitopes that have increased binding affinity to antigen presenting immune cells thus mounting an immune response

The enzyme is released by inflamed cells and is the primary antigen for autoantibodies of celiac disease patients

Anti-Gliadin titers correlate with the inflammation and with the condition of the mucous membrane of the small intestine

Question 15

Anti-DGP (deamidated gliadin peptide) Test description
Determining level of IgA antibodies make it possible to … (2)

Answer 15

• ELISA
• In serum samples from celiac patients, IgA and IgG antibodies against deamidated gliadin peptide epitopes are found.

The IgA antibodies make it possible to
1.determine the level of disease activity
2.monitor adherence to a gluten-free diet.

Question 16

Endomysial antibodies Test
test type
substrate

Answer 16

Immunofluorescence assay to detect IgA
The endomysium is connective tissue that lines muscle fibers, and it contains a form of TTG. Antibodies that bind TTG in endomysial tissue are called endomysial antibodies, and they are highly specific for celiac disease.

Indirect immunofluorescence using monkey oesophagus. Substrate used is primate oesophagus

Staining indicates a unique pattern

Question 17

Diabetes Causes and Symptoms

Answer 17

Pancreas fails causing the inability to make insulin or use the insulin in the body

Excessive thirst
Fatigue
Frequency urination
Weight loss/gain

Question 18

Hasimoto Causes and Symptoms

Answer 18

AID causing the thyroid gland to be destroyed by immune system causing low production of thyroid hormones

Intolerance to cold
Constipation
Dry hair/hair loss
Giotre
Irregular menstrual cycle
Weight gain

Question 19

Graves Causes and Symptoms

Answer 19

AID causing the thyroid gland to over produce thyroid hormones

Bulging eyes
Diarrhoea
Fatigue
Goitre
Heat intolerance
Rapid, pounding and irregaulr heart rate
weight loss

Question 20

Hyperthyroidism and Hypothyroidism Causes and Symptoms

Answer 20

Hyper: Overactive thyroid gland (same as Graves)

Hypo: Underactive thyroid gland (same as hashimoto)

Question 21

Process of Graves and Hashimoto starting at genetic and environmental factors

Answer 21

Lecture Slide

Question 22

Information about Graves disease..
Raises what?
Causes?
Genetic and environmental causes examples

Answer 22

causes goiters, hyperthyroidism, ophthalmopathy, and occasionally dermopathy.

Decrease in thyroid-stimulating hormone (TSH)
raises the thyroxine (T4) levels - hyperthyroidism
in approximately 10% of cases, an increase in triiodothyronine (T3) levels.

has both genetic causes, such as a lack of suppressor t-cells causing an increase in TSH receptor antibodies, and environmental causes which includes, stress, smoking, postpartum, and infections

Question 23

Test results for Graves, Hashimoto, Secondary hypo
Sick euthyroid

TSH, T3, T4 and antibodies

Answer 23

Graves
TSH: Low
T3: High
T4: High
Antibodies: Anti-TSH

Hashimoto
TSH: High
T3: Low
T4: Low
Antibodies: Anti-TPO, anti-Tg

Secondary hypo
TSH: Low
T3: Low
T4: Low

Sick euthyroid
TSH: High
T3:Low
T4: Low

Question 24

Diabetes 1 description

Answer 24

causes the level of glucose in your blood to become too high

your body is not able to produce enough insulin (hormone), which controls blood glucose

mainly diagnosed in childhood

Question 25

Diabetes type 1 signs/symptoms

Answer 25

The signs and symptoms of type 1 diabetes can appear suddenly. The classic symptoms are:
Excessive or constant thirst
Frequent urination (peeing)
Extreme hunger

Other signs and symptoms include:
Unexplained weight loss
Nausea
Fatigue and weakness
Blurred vision
Irritability
Bedwetting in children
Vaginal thrush

Question 26

Diagram of type 1 diabetes

Answer 26

Lecture slide

Question 27

Type 1 vs Type 2

Answer 27

Lecture slide

Question 28

Diagnose Diabetes

Answer 28

classic symptoms of diabetes
Blood glucose
Random blood glucose test
Fasting blood glucose test
Oral glucose tolerance test

HbA1c (glycosylated haemoglobin)
a measure of a person’s average blood glucose level over the past 2–3 months
monitor the effect of treatment

Question 29

Describe the pathophysiology of crohns and UC + diagram

Answer 29

Lecture Slide
There is damage to the M cells or barrier function of the intestinal epithelial cells causing the microbials to enter and are phagocytosed by APC. This activates the immune response by activating CD4+ cells which stimulate macrophages to released cytokines (TNF-alpha, IL1/6) which cause the chronic inflammation and therefore systemic and local complications. TNF-alpha has the role in angiogenesis, increased immune response, intestinal cell death and myofibral tissue damage.

Question 30

why are Endomysial IgA made in celiac ?

Answer 30

Tissue Transglutaminase (tTG): Tissue transglutaminase is an enzyme found in various tissues, including the endomysium, which is a connective tissue that surrounds muscle fibers.

Immune Response: In celiac disease, when gluten is ingested, it triggers an immune response in the small intestine. Part of this immune response involves the production of antibodies against gluten.

Antibodies Against tTG: As part of the autoimmune response triggered by gluten, the immune system produces antibodies, including EMA IgA, that target tissue transglutaminase (tTG). These antibodies are specific to tTG.

Damage to the Intestine: When EMA IgA antibodies bind to tTG, they contribute to the autoimmune damage that occurs in the small intestine. This damage is a hallmark of celiac disease and results in inflammation and villous atrophy (damage to the finger-like projections called villi) in the small intestine.

So, EMA IgA antibodies are not directly targeting the endomysium itself but rather tissue transglutaminase, which is present in the endomysium and other tissues. The production of EMA IgA antibodies is a key feature of the autoimmune response in celiac disease, leading to intestinal damage and the characteristic symptoms of the condition.

Question 31

EMA IgA test method

Answer 31

A patient’s serum, which contains antibodies (in this case, EMA IgA antibodies), is applied to tissue sections (e.g., primate esophagus). This tissue contains the endomysium, a connective tissue component that surrounds muscle fibers and contains tissue transglutaminase (tTG)

If EMA IgA antibodies are present in the patient’s serum, they will bind to the TTG in the endomysium on the tissue section.

A secondary antibody labeled with a fluorescent dye (typically an anti-human IgA antibody) is applied. This secondary antibody specifically binds to any EMA IgA antibodies that have attached to TTG in the endomysial tissue.

When the prepared slide is examined under a fluorescence microscope, any EMA IgA antibodies bound to the endomysium will emit fluorescence when exposed to specific wavelengths of light. A positive result suggests that the patient’s immune system has produced antibodies against tTG, which is a characteristic feature of celiac disease

The pattern of fluorescence produced in the tissue is characteristic of EMA IgA antibodies binding to the endomysium, and this pattern is used as a diagnostic marker for celiac disease.

Question 32

Why do the symptoms of andominal pain, blaoting, doarrhoea happen

AND

why do coeliac people have stinky stool, anaemia and failure to thrive

Answer 32

The inflammation caused by the cytokines released by CD4 and CD8 activated cells against the intestinal linin causes those symtpoms

Stinky stool due to the lack of finger like projections allowing the absorption of iron, B12 (ANEMIA), nutrients (FAILURE TO THRIVE) and fats (STEATORRHOEA)

REFER TO DIAGRAM

Question 33

2 additonal functions of TTG other than deamidation gluten

Answer 33

1. Involved in the process of tissue repair and wound healing. It helps in the formation of a stable fibrin clot by cross-linking fibrinogen, which is important for blood clotting
2. TGase is responsible for catalyzing the formation of covalent bonds between protein molecules. This cross-linking helps stabilize the structure of tissues and proteins, making them more resistant to degradation.

Question 34

Testing alogthrim:
1. Suspected patient
2.relative with coeliac history
3.Coeliac known patient

Answer 34

1. Suspected patient
   TtG IgA
   POS = Duodenual biopsy to confirm
   NEG = unrelaible if IgA deficent, or TRUE neg

2.relative with coeliac history
Perform TtG IgA
POS = duodenual biopsy

3.Coeliac known patient
TtG for monitoring
HIGH - observe diet

Question 35

how does IgA deficent affect testing?

Answer 35

Anti-TTG and Anti-EMA are both IgA antibodies and therefore IgA def (shown through testing total IgA) causes a decreased starting level of anti-TTG and anti-EMA and therefore leading to a FALSE NEGATIVE. As no matter if the celiac is severe, the deficency will always cause a low level of these antibodies. SO test for IgG version of these antibodies.

Question 36

Explain why celiac causes these parameters:
LOW albumin
LOW Hemoglobin
LOW Ferritin, folic acid, B12
POS TTG
HIGH Fecal fat

Answer 36

The intestine is lined with villi that absorb nutrients from the liquid mixture called chyme produced in the stomach from the food we eat. So causes low albumin due to villi atrophy causing lack of absorption of amino acids needed for the liver to make albumin. This combined with the diarrhoea, bloating and abdominal pain this causes a lack of desire to eat causing lack of food intake and thus proteins.

The lack of iron able to be absroped from food from the villi in the intestine causes malabsorption. Therefore the biody cant absorb any or adequate levels of iron from foods causing low serum iron and results in the use of stored iron (ferritin) and draining this source.
Iron is used to make hemoglobin and is the majority of these molecule, without it hemoglobin cant be made and therefore causes the anaemia/lack of RBC (made of hemoglobin).

This malabssorpin causes B12, folate etc deficencies and the high fecal fat.

Question 37

Cause of celiac disease

Answer 37

1. Family History
   - Celiac disease is hereditary, meaning that it runs in families. People with a first-degree relative with celiac disease (parent, child, sibling) have a 1 in 10 risk of developing celiac disease.
   - HLA DQ2/8: around 90% have variants of these HLA and causes celiac disease to occur upon consumption of gluten.
2. Other autoimmune conditions
   - TD1
   Both type 1 diabetes and celiac disease have a strong association with specific genes in HLA complex. In the case of type 1 diabetes, the HLA genes DR3 and DR4 are most strongly associated with the disease. In celiac disease, the HLA-DQ2 and HLA-DQ8 genes are closely linked to an increased risk. Some individuals may carry variants of these genes or genetic overalp that make them more susceptible to both conditions.
3. Genetic conditions
   - Downs syndrome
   -Williams syndrome
   Turner Syndrome
   People with genetic syndromes like Turner syndrome, Williams syndrome, and Down syndrome may have unique genetic variations that can increase the likelihood of having the HLA-DQ2 or HLA-DQ8 genes. These genetic syndromes can affect the composition and expression of genes in various ways, which may contribute to an increased risk of carrying these HLA genes. Also these conditions are known to have immune systme dysfunction causing individuals more susceptible to celiac disease.

the genetic influence from having an extra chromosome 21, in combination with a specific genetic variation on at least one other chromosome, leads to the development of celiac disease

4. Infections
   - Adenovirus type 12, HCV, Campylobacter jejuni, Giardia lamblia, enterovirus, and rotavirus trigger celiac. Viral infections, such as with adenovirus or hepatitis C, have long been known to be associated with a higher risk of developing CeD (induce loss of oral tolerance to gluten and dietary antigens). Specific viruses were capable of mediating TH1 responses to dietary antigens.

Some viral infections of the intestine alter the immune response to oral antigens such as gluten and lead to development of CD. Examples are Reovirus strains stimulates type 1 IFNs leading to this change in intestinal environment.

5. Childhood
   -Early and substantial exposure of infants to dietary gluten (Children exposed to gluten in the first 3 months of life have a 5× increased risk of CD compared with children exposed to gluten at between 4 and 6 months of age. Children exposed to gluten after 7 months have a marginally increased risk of developing CD in comparison with those exposed at 4–6 months)

The primary trigger for celiac disease is the consumption of gluten-containing foods. Gluten is found in wheat, barley, and rye, as well as in related grains like spelt and triticale. Even small amounts of gluten can trigger the immune response in individuals with celiac disease.

6. early infection with enteropathic viruses (interfere with the maturation of the mucosal immune system and the composition of the microbiome and thus favor the subsequent induction of an inflammatory T cell responses and the loss of oral tolerance to dietary gluten)

Question 38

TWO tests for diagnose celiac disease

Answer 38

Serology Tests:
a. Anti-tissue transglutaminase antibodies (tTG-IgA) and Anti-endomysial antibodies (EMA-IgA)

Endoscopy with biopsy of the duodenum. Small samples of tissue (biopsies) from the lining of the duodenum is taken and observed under microscope for villi atrophy, lymphycte infiltration and crypt hyperplasia.

Question 39

why does HLA cause activation of T cells (deem gluten as foreign in some but not in others)

Answer 39

Specific variants or alleles of the HLA-DQ2 and HLA-DQ8 genes are associated with increased risk of developing celiac disease due to their immunogenic properties. These variants create a specific HLA protein structure that has a high binding affinity for gluten-derived peptides and allows for enhanced antigen presentation to T cells all leading to enhanced immunogenicity. The peptide-binding properties of HLA-DQ2 are linked directly to disease development. This was confirmed by the observation of gliadin specific, HLA DQ2-restricted T cells are commonly found in small intestinal biopsies from coeliac disease patients

α-gliadins constitute the most immunogenic fraction since they contain the main T-cell stimulating epitopes causing the activation of HLA restricted T cells as this is what is recongised as foreign.

Gluten-reactive T cells are a hallmark of celiac disease. These cells recognize DGP presented on disease-associated HLA-DQ molecules and play pivotal roles in the pathogenesis of celiac disease. As due to being HLA-DQ2/8 restricted, if gluten is bound to the HLA, it will cause the activation of these T cells and the cells will recongise the α-gliadins as foreign. CD4+ T cells reactive to these epitopes of gluten can only be found in the intestinal tissue of celiac disease patients indicating that theses gluten specific TH1 cells are celiac specific due to the presence of disease-associated HLA-DQ molecules.

Therefore, HLA class II molecules are expressed on the surface of APC where they can bind and subsequently present “foreign” α-gliadins peptides to of CD4 T cells which recognize the DQ2- or DQ8-peptide complex. Once bound these complexes activate DQ2 or DQ8 restricted T cells in the small intestinal mucosa driving TH1 differentiation . These gluten-specific TH1 cells contribute to the inflammatory process through the production of the inflammatory cytokines Interferon (IFN)-γ and Interleukin (IL)-21

Question 40

Describe the Gold standard test for Celiac disease and the expected results

Answer 40

Intestinal duodenal endoscopy and biopsy

The biopsy is usually performed during an upper gastrointestinal endoscopy. During the EGD, the patient is sedated, and a flexible, thin tube (endoscope) with a camera at the tip is passed through the mouth and into the stomach and duodenum.

Biopsy: Once the endoscope is in the duodenum, forceps take several tiny tissue samples (biopsies) from the lining of the duodenum.

Expected Celiac Results:
1.Villous Atrophy:
villi that line the small intestine are flattened or blunted. This reduces the surface area available for nutrient absorption. When the T cells encounter these antigen-presenting cells in the mucosa, they release inflammatory cytokines, such as interferon-gamma and tumor necrosis factor-alpha. The cytokines and immune response lead to inflammation in the small intestine, particularly in the villous structures that project from the intestinal lining. The inflammation, in turn, causes damage to the intestinal villi. Over time, the continuous inflammation and immune response result in damage to the intestinal villi. This damage includes a flattening and shortening of the villi, which is referred to as villous atrophy. Villous atrophy significantly reduces the surface area available for nutrient absorption in the small intestine

2. Lymphocyte infiltration:
   In celiac disease, there is an increase in the number of lymphocytes within the epithelial layer of the small intestine.
   - The activated CD4+ T cells migrate to the lining of the small intestine (the mucosa). This is where the gluten is digested and processed, and where they encounter antigen-presenting cells displaying gluten peptides. When these T cells encounter these antigen-presenting cells in the mucosa, they release cytokines and other signaling molecules that further stimulate the immune response. The release of cytokines by the activated T cells leads to inflammation in the small intestine. This inflammatory response recruits more immune cells, including other lymphocytes (such as B cells), to the site of inflammation. This results in the infiltration of lymphocytes into the intestinal lining

3.Crypt Hyperplasia: Crypts become longer and more numerous
- increase in length of crypts
- increase in the number of cells within the crypt as well as the length of the cyrpt. This is because the crypts are the sites of active cell production in the small intestine. When the body senses damage, it stimulates the production of new epithelial cells in the crypts to replace damaged cells and maintain the integrity of the intestinal barrier. Therefore, crypt hyperplasia can occur as a compensatory mechanism to counteract the shortening of the villi (longer crypts make the villi appear longer).

4. Inflammation: Inflammation of the intestinal lining upon endoscopy often present.

To confirm a diagnosis of celiac disease, pathologists will typically look for a combination of these features, particularly villous atrophy and increased IELs. The degree of damage seen in the biopsy can also help gauge the severity of the disease. It’s important to note that a normal biopsy does not definitively rule out celiac disease, as the disease can be patchy, and the damage may not be present in every part of the small intestine. Additionally, it’s essential to consider the patient’s clinical symptoms, serologic test results, and genetic markers in the diagnostic process.

Question 41

Why is it the GOLD standard

Answer 41

Direct Visualization of Tissue Damage: Intestinal biopsy involves the direct visualization and examination of the tissue in the small intestine. It allows healthcare professionals to see and assess the characteristic damage that occurs in celiac disease, such as villous atrophy and inflammation. This visual confirmation is highly specific and hallmarks of celiac disease.

Objective Measurement of Mucosal Damage: Biopsy provides an objective measurement of the extent of mucosal damage. This is essential for determining direct severity of the disease and guiding treatment decisions. The severity of villous atrophy can vary among individuals with celiac disease, and biopsy quantifies this damage accurately

Confirmation of Diagnosis: While serologic blood tests, such as measuring antibodies like tTG-IgA and EMA-IgA, can provide preliminary indications of celiac disease, they are not conclusive on their own and are subject to interferences such as IgA deficency, false increase (HIV) or false low (igA deficency). The duodenal biopsy is essential for definitively confirming the diagnosis. It reveals characteristic histological changes in the intestinal lining that are unique to celiac disease. Other tests like serology can produce variable results, including false positives and negatives, and they are less specific than histological examination. Other conditions can also lead to elevated antibody levels, causing potential confusion

Distinguishing from Similar Conditions: Celiac disease shares symptoms with other gastrointestinal disorders, such as Crohn’s disease and irritable bowel syndrome. The biopsy is crucial for defiantly distinguishing celiac disease from these conditions.

Validation of Genetic Testing: Genetic testing can identify the presence of HLA-DQ2 and HLA-DQ8 genes associated with celiac disease. However, it cannot diagnose active celiac disease and some people with celiac lack these genetic marker due to the multifactorla causes of celiac.

Monitoring Disease Progression: Intestinal biopsies can be used to monitor the direct progression of celiac disease and assess the healing of the intestinal lining in response to a gluten-free diet. This is crucial for evaluating the effectiveness of treatment and guiding long-term management.

An intestinal (duodenal) biopsy is considered the “gold standard” for diagnosis because it will tell you (1) if you have celiac disease, (2) if your symptoms improve on a gluten-free diet due to a placebo effect (you feel better because you think you should) or (3) if you have a different gastrointestinal disorder or sensitivity which responds to change in your diet.