SHOW NOTES

Using TTG for celiac diagnosis compared to biopsy [0:45]

• Biopsy - invasive, costly, but most definitive diagnostic test for celiac disease
• Can miss information if you don’t have a biopsy
• Can use anti-tissue transglutaminase antibodies to determine if patient should proceed to biopsy
• Antibodies towards the specific enzyme tissue transglutaminase
• Can be IgA or IgG derived
  

Tissue transglutaminase definition [3:00]

• Not an antibody, but can have antibody reaction associated with it
• Tissue transglutaminase is an enzyme that in celiac disease patients is highly dependant on the mineral calcium
• Tissue transglutaminase combined with calcium caused the transamidation of proteins
  • Transamidation = transferring an amide group (COHN2) from one compound to another & changing the chemical structure
    • Taking compound of atoms and switching the way they’re put together
• TTG is part of a family of enzymes known as protein-glutamine gamma-glutamyltransferases [4:50]
  • These enzymes catalyze & stimulate the modification of proteins (the building blocks within the body)
  • Structure changes can make the protein look so foreign and unrecognizable to the immune system that the immune system will bind to & attack it
  • Causes protein modifications at specific sites (side-chains) of amino acids (broken down protein)
    • Amino acids such as lysine & glutamine
      • Lysine residue can cause crosslinking
    • Involved in process called deamidation - changing structure
    • Through enzymatic activity, converting amino acids into completely different amino acids
      • Glutamine into glutamic acid
      • Asparagine into aspartic acid
• Amide: substance that contains group of molecules, that is being transferred over to something else which changes the chemical structure
• In organic chemistry, conversion of amide to carboxylic acid [6:30]
  • Carboxyl group is carbon + 2 oxygen + 1 hydrogen on every fatty acid
  • Conversion of amide to carboxylic acid causes end result of leaving different protein structure that is either completely or highly resistant to being broken down through enzymes & digestion
    • Process known as proteolysis - enzyme protein breakdown
    • Proteolysis is incredibly slowed down or stopped when amide is converted to carboxylic acid
• Tissue transglutaminase are found throughout the human body, even in those without celiac disease
  • Part of a family of enzymes known as protein-glutamine gamma-glutamyltransferases
  • Used during apoptosis (signal when cells are done growing and terminate)
  • Involved in metastatic cancers
  • Involved in neurodegenerative diseases
  • Enzyme found in heart muscle tissue
  • Elevated levels of TTG are a crucial link for celiac disease progression

Gluten vs. glutamine vs. glutaminase - they’re all different [8:45]

• TTG is the enzyme that plays a role in changing the protein structure within the gluten protein gliadin
  • TTG changes gliadin’s charge and structure as a molecule
  • Morphs it into a structure the body sees as a threat
• TTG = enzyme
• Gluten  = a protein group found in foods
• Glutamine = an amino acid critical for gut health, specifically the small intestine
  • Makes other substances in the body

TTG within celiac disease patients [10:55]

• Celiac person consumes gluten → gluten enters duodenum (area of small intestine) where digestion and absorption of key minerals occurs → gluten taken up by submucosa (second layer of the intestinal lining)→ results in a production of antibodies to TTG
• TTG appears when gluten is in the submucosa
• TTG is released as a sign of injury and inflammation
• TTG is hard at work on the gluten molecule to change its charge and structure
  • Creates binding to unique celiac genes HLADQ2 & HLADQ8
• Immune system reaction, TTG changes structure of gluten molecule, fosters binding of new gluten molecule to HLA gene receptors which stimulates pro-inflammatory autoimmune cytokine response
  • Interferon gamma, lymphocyte presence, gliadin specific CD4 T-cells
• Autoimmune response in celiacs causes atrophy (breakdown) of villi and microvilli while also opening intestinal tight junction cells to allow antigen & antibody response to travel outside gastrointestinal tract, circulating through the bloodstream to other parts of the body
  • Due to the circulation, shows up in a blood test for the majority

TTG antibodies are specific [13:40]

• Antitissue transglutaminase antibodies are specific to an immunoglobulin
  • Immunoglobulins have different letters & different functions
• Predominant immunoglobulin in the gastrointestinal tract is sIgA - secretory immunoglobulin IgA
  • Starts floating around in bloodstream attached to a TTG gluten-based structure as an enemy calling the immune system to attack it

TTG Blood Tests for celiacs [14:45]

• Most common TTG test for celiacs is tissue transglutaminase IgA (TTG IgA)
  • Has sensitivity & specificity of over 90% in children and adults
  • Sensitivity = ability to identify individuals with the disease (true positive rate)
  • Specificity = ability to identify individuals without the disease (true negative rate)
    • Children sensitivity: 93.1 - 95.7%
    • Children specificity: 96.3 - 99%
    • Adult sensitivity: 90 - 95%
    • Adult specificity: 95.3 - 98%

Dr Pastore recommends additional testing beyond TTG IgA [17:00]

• Start with secretory immunoglobulin IgA, or l run with the TTG IgA with a sIgA total
  • Celiac patients have a 15x greater change of total IgA deficiency
    • Well below “normal” reference range
      • Less than 1
      • Check aged-matched values (levels based on age)
    • Don’t produce sufficient antibodies/antigens to test for a reaction to gluten
  • TTG IgA would not flag a celiac on a blood test if sIgA is deficient
• If you’re deficient in total IgA, try TTG IgG
  • Gliadin deamidated antibody IgG (DGGL) blood test
  • Don’t need a TTG IgG if you have sufficient sIgA
    • Used when sIgA is deficient but still believe it could be celiac disease
• TTG IgA and TTG IgG and DGLDN blood test should be run when sIgA based on age is below normal

When sIgA is normal, TTG IgA numbers mean….[22:00]

• As per the Mayo Clinic scale
• 4.0 - 10.0 units/mL of anti-TTG IgA antibodies for gluten is equivocal (potential)
  • Don’t wait, continue testing for a definitive answer
  • Run a DAGL (gliadin deamidated antibody IgA) and Endomysial antibody IgA
    • Endomysial antibody IgA is expensive, may not be 100% accurate but necessary to get a true diagnosis
• Over 10 units/mL go straight to biopsy
  • Still get the biopsy to be definitive - could be elevated for other reasons
  • No one test is 100% accurate
  • Biopsy can also provide additional pathology - small intestinal cancer, secondary infections, h-pylori & ulcers

Must be consuming gluten for antibody to be TTG tests to be accurate for celiac disease testing [24:30]

• TTG has 2 critical roles in celiac disease
  • Enzyme acts upon gluten & creates immunological event to connect it with the HLA celiac genes
  • Gives target auto-antigen for immune system response to measure
• Gliadin (fragment in gluten) causes TTG to elevate via IgA or IgG
• Small amounts of gluten such as one crouton should be sufficient for testing
  • “It takes a crumb”
  • In general, 20 parts per million exposure will trigger the immune reaction & cytokine storm in the gut

Once diagnosed as a celiac, get your TTG IgA and/or TTG IgG reevaluated at 3 and/or 6 months, and 12 months after diagnosis [32:00]

• Repeat any tests that were done to diagnose celiac disease
• Shows healing of gastrointestinal tract & show any instances of gluten exposure
• In Dr. Pastore’s practice, if someone had TTG IgA of 10 to be diagnosed, it should drop down to 4-7 in first 3-6 months of being militantly gluten-free, then below 4 by month 12
  • Downward trend is ideal
  • If TTG IgA is increasing or not going down, likely consuming gluten unknowingly
    • Spices, condiments, supplements, medications all have hidden gluten
• Get TTG IgA retested at yearly physical check up too, elevated after being normal requires investigation for unknown gluten contaminants

Diagnosis pathway [39:00]

• (Genetics) → Bloodwork → Biopsy
• If you have the gene, you still may not have celiac disease
• If you don’t have the gene variances, you can’t have celiac disease (but can still have a gluten intolerance)
• sIgA and TTG IgA and/or TTG IgG should show first warning signs

Wrap-Up [42:30]

• Help your doctor help you - provide them with the resources they need to diagnose you
• www.drrobetpastore.com & @drrobetpastore

To share with your physician:

Diagnosing celiac disease accurately

Recommendations by Dr. Robert Pastore, PhD, CNS & Celiac

Rather than start with a TTG IgA, I prefer to either start with sIgA or run an sIgA in addition to the TTG IgA so that we do not miss any chance for IgA insufficiency (there is a 15 fold increase risk for sIgA deficiency in celiac disease).

In the case of a selective IgA deficiency, we need to run TTG IgG and Gliadin deamidated antibody IgG (known as a DGGL blood test).

Now if the sIgA is below age-matched values then we run the TTG IGA and IGG along with DGLDN (gliadin deamidated antibodies IgG and IgA.

If the sIgA is completely normal or elevated, then we simple look at the TTG IgA results and see where they land on a scale. Using the Mayo Clinic scale as a reference, if TTG IgA is between 4.0 U/mL and 10 U/mL I do like a follow up that includes DAGL (gliadin deamidated antibody IgA) and Endomysial antibody IgA.

If the TTG igA is greater than 10 U/mL that patient should be referred directly to a biopsy.

For more information, consult “Physician Review of a Celiac Disease Risk Estimation and Decision-Making Expert System” - PubMed ID: 31063433