Why Antibody Tests Matter

Blood tests are usually the first step in celiac diagnosis. Understanding them helps you understand your diagnosis, and your ongoing monitoring.

The Basic Concept

In celiac disease, your immune system produces antibodies against:

1. Gluten (specifically, modified gluten proteins)
2. Your own tissue (specifically, tissue transglutaminase)

Blood tests detect these antibodies. Their presence suggests celiac disease; their absence (after treatment) suggests the diet is working.

The Main Tests

tTG-IgA (Tissue Transglutaminase IgA)

What it is: Antibodies against tissue transglutaminase, an enzyme in your body.

Why it matters: This is the primary screening test for celiac disease. It’s:

• Highly sensitive (catches most cases)
• Highly specific (positive results usually mean celiac)
• Relatively inexpensive
• Good for monitoring

Numbers:

• Normal: Typically below a cutoff (varies by lab)
• Mildly elevated: Suggests possible celiac
• Highly elevated: Strongly suggests celiac

After diagnosis: Should decrease on GF diet. Many doctors use this for monitoring, checking periodically to see that levels remain normal/low.

Total IgA

What it is: Your overall IgA antibody level.

Why it matters: About 2-3% of celiacs are IgA deficient. If you can’t make IgA, tests that rely on detecting IgA will be falsely negative.

How it’s used: Run alongside tTG-IgA to rule out IgA deficiency. If total IgA is low, different tests (IgG-based) are used.

EMA (Endomysial Antibodies)

What it is: Antibodies against endomysium (connective tissue in muscle).

Why it matters:

• Very specific (positive almost always means celiac)
• Good confirmatory test
• More expensive and labor-intensive than tTG
• Often used to confirm borderline tTG results

DGP (Deamidated Gliadin Peptide)

What it is: Antibodies against modified gluten proteins.

Why it matters:

• Useful in IgA-deficient patients (DGP-IgG)
• May be positive earlier in disease development
• Good for monitoring in some cases

Anti-Gliadin Antibodies (AGA)

What it is: The older test for celiac, detecting antibodies against gliadin (a gluten component).

Why it matters:

• Less specific than newer tests
• Not recommended for diagnosis anymore
• May still be used in research or specific situations

How the Tests Are Used

For Diagnosis

Standard approach:

1. tTG-IgA + Total IgA (screening)
2. If positive/borderline: Possibly EMA confirmation
3. If Total IgA is low: Use IgG-based tests
4. Positive serology → Endoscopy with biopsy (still gold standard for confirmation)

Some newer protocols in pediatric patients allow diagnosis without biopsy if tTG-IgA is highly elevated (>10x normal) and EMA is positive. This is not universal.

For Monitoring

After diagnosis and starting the GF diet:

What most doctors do:

• Check tTG-IgA periodically (every 6-12 months initially, then annually)
• Look for normalization (antibodies returning to normal range)

What it tells you:

• Decreasing antibodies → Diet is working, healing is happening
• Persistently elevated → Possible ongoing gluten exposure (intentional or not)
• Rising after being normal → Something changed (gluten exposure)

Limitations:

• Antibody levels don’t correlate perfectly with intestinal healing
• Some people heal faster/slower than antibodies suggest
• Not a replacement for how you feel

Interpreting Your Results

At Diagnosis

High tTG-IgA + Positive EMA + Intestinal damage on biopsy → Definitive celiac disease

Positive serology + Normal biopsy → Possible early/potential celiac, may need follow-up

Negative serology + Positive biopsy → Less common, but possible (seronegative celiac)

Negative serology + Normal biopsy → Celiac unlikely (assuming you were eating gluten)

On Treatment

tTG-IgA normalizes: Great, your immune system is calming down

tTG-IgA decreasing but not normal yet: Progress; give it more time

tTG-IgA staying elevated: Suggests ongoing gluten exposure; investigate sources

tTG-IgA rises after being normal: Red flag, something is introducing gluten

Why “Must Be Eating Gluten”

Antibody tests only work if you’re being exposed to gluten. If you’re already GF:

• Antibodies will be low/negative even if you have celiac
• The test can’t detect a disease that isn’t currently active
• This is why diagnosis before starting GF diet is important

If you went GF before testing and now want diagnosis, you may need to do a “gluten challenge”, eating gluten for several weeks before testing. Discuss with your doctor.

Common Questions

How often should I be tested?

After diagnosis:

• First year: Every 6-12 months
• After stabilization: Annually (or as doctor recommends)
• If symptoms recur: Test to check for exposure

My levels are normal but I don’t feel great. What gives?

Antibody normalization doesn’t equal complete healing or symptom resolution:

• Intestinal healing lags behind antibody changes
• You might have other issues (lactose intolerance, etc.)
• Symptoms can persist despite serological improvement

My levels are elevated but I’m strict about GF. What’s happening?

Possibilities:

• Hidden gluten sources you haven’t identified
• Cross-contamination
• Your body is slow to normalize (give it more time)
• Rarely: refractory celiac disease

Work with your doctor to investigate.

Can I use home tests?

Home celiac screening tests exist. They’re:

• Less reliable than lab tests
• May give false negatives
• Not recommended as sole diagnostic tool
• Possibly useful for monitoring if unable to access lab tests

Lab tests through your doctor are preferred.

The Bigger Picture

Antibody tests are tools:

• They help diagnose
• They help monitor
• They provide objective data

But they’re not the whole picture. How you feel, how your intestines look on biopsy, your nutritional status, all matter too.

Use the tests as information, not as the only measure of your health.