Antigliadin Antibodies: Test Purpose and Results Explained

Antigliadin antibodies (AGA) are immune proteins your body produces in response to gliadin, a component of the gluten found in wheat, barley, and rye. The test measures these antibodies in your blood and was once a frontline tool for diagnosing celiac disease, but it has largely been replaced by more accurate tests. AGA testing still has a role today, though it is narrower and more specialized than most people expect, showing up in the workup for non-celiac gluten sensitivity, certain neurological conditions, and specific situations where newer tests fall short.

What Gliadin Does in the Body and Why Antibodies Form

Gliadin is one of the main protein fractions in gluten. When you eat wheat bread or pasta, digestive enzymes break most proteins down into small, harmless fragments. Gliadin is different: parts of it resist full digestion, leaving larger peptide fragments intact in the gut. In people who are genetically susceptible, these undigested fragments trigger immune responses. One pathway involves the adaptive immune system, where specialized T cells recognize the gliadin fragments as foreign and mount an attack against the gut lining. Another involves the innate immune system, where the gliadin fragments provoke stress responses in the cells lining the small intestine, driven partly by the signaling molecule interleukin-15.

As part of these immune reactions, the body produces antibodies targeted at gliadin itself. These are the antigliadin antibodies. They come in two main types: IgA (the antibody class that dominates in mucosal surfaces like the gut) and IgG (a more general antibody found throughout the bloodstream). The IgA version tends to be more diagnostically useful for celiac disease, while the IgG version shows up in a wider range of conditions and is the main marker studied in non-celiac gluten sensitivity.

Why AGA Fell Out of Favor for Celiac Diagnosis

For decades, AGA IgA and IgG were among the few blood tests available to screen for celiac disease. That changed as researchers developed tests targeting tissue transglutaminase (tTG) and endomysial antibodies (EMA), which turned out to be far more accurate. A study comparing the older AGA test to these newer markers found that serum IgA antigliadin antibody had a sensitivity of about 84% and specificity of 95% for detecting untreated celiac disease, which sounds reasonable until you compare it to what came next.¹ Modern tTG IgA assays now achieve sensitivity and specificity around 99% and 100%, respectively, with excellent agreement with EMA testing.² That gap matters. A test with 95% specificity will flag roughly one in twenty people who don’t actually have celiac disease, leading to unnecessary worry and follow-up biopsies.

Research evaluating AGA directly against newer serological markers concluded that traditional gliadin antibodies generally lack the accuracy required for proper celiac diagnosis.³ Most current clinical guidelines no longer recommend conventional AGA as a first-line celiac screening test. If your doctor is testing for celiac disease, you will almost certainly get a tTG IgA test, possibly alongside an EMA test, rather than an AGA panel.

Deamidated Gliadin Peptide Tests Are Not the Same Thing

A common point of confusion: when labs report “gliadin antibodies” today, they may be measuring antibodies to deamidated gliadin peptides (DGP) rather than to native, unmodified gliadin. These are different tests with different performance characteristics. Deamidation is a chemical change that gliadin undergoes inside the body, catalyzed by the enzyme tissue transglutaminase. The modified peptides are more strongly recognized by the immune system in celiac disease, which makes antibodies against them more specific for the condition.

Tests for anti-DGP antibodies showed higher diagnostic accuracy than traditional antigliadin antibodies and, while slightly less sensitive than tTG and EMA tests, demonstrated significantly higher specificity than tTG for ruling out false positives.⁴ If your lab report mentions “anti-DGP” or “deamidated gliadin peptide antibodies,” that is this newer, more accurate test. If it says “anti-gliadin” or “AGA” without the word “deamidated,” it is the older, less specific test. The distinction matters for how confidently you and your doctor can interpret the result.

When AGA Testing Still Matters

Even though AGA has been sidelined for routine celiac screening, there are situations where it remains clinically useful or is the primary marker under investigation.

IgA Deficiency

Selective IgA deficiency is the most common primary immune deficiency, and it occurs at higher rates in people with celiac disease than in the general population. The problem is that most celiac screening tests measure IgA-class antibodies. If your body doesn’t produce much IgA, those tests come back negative even if you have active celiac disease, a classic false negative. In one Italian study, every IgA-deficient celiac patient tested negative for IgA gliadin and IgA endomysial antibodies, but almost all of them had high IgG antigliadin antibodies.⁵ IgG-based tests for gliadin, endomysium, and tissue transglutaminase all proved useful in identifying celiac disease in IgA-deficient patients.⁶

That said, IgG AGA alone is not always reliable in this group. One study found that while all IgA-deficient celiac patients tested positive for IgG anti-tissue-transglutaminase, only about half were positive for IgG antigliadin. Meanwhile, every patient who tested positive for IgG AGA alone, without a positive tTG result, turned out to have a normal biopsy.⁷ So IgG AGA can contribute to the workup in IgA-deficient patients, but it performs best when interpreted alongside IgG tTG rather than on its own.

Non-Celiac Gluten Sensitivity

Non-celiac gluten sensitivity (NCGS) is a condition where people experience digestive and systemic symptoms after eating gluten but do not have celiac disease or a wheat allergy. There is no definitive blood test for NCGS, but AGA IgG is the antibody that shows up most often in these patients. In a Japanese study of individuals with suspected NCGS, about a third tested positive for AGA IgG, compared to about 13% of controls.⁸ That’s a statistically significant difference, but the sensitivity of only about a third means two out of three people with NCGS will test negative. The specificity was better, around 87%, meaning most people without NCGS will test negative.

Other researchers have been less optimistic. An analysis using multiple statistical approaches found that AGA IgG had poor overall diagnostic accuracy for NCGS.⁹ The honest state of the science is that a positive AGA IgG test in someone with gluten-related symptoms and a negative celiac workup is suggestive of NCGS, but a negative result doesn’t rule it out. NCGS remains a diagnosis made primarily by excluding celiac disease and wheat allergy, then observing symptom improvement on a gluten-free diet, rather than by any single blood marker.

AGA IgG as a Monitoring Tool on a Gluten-Free Diet

One area where AGA IgG has shown genuine practical value is tracking the immune response to dietary change. In a study of NCGS patients who adopted a strict gluten-free diet, over 93% saw their IgG antigliadin antibodies disappear within six months. By contrast, only about 60% of celiac patients cleared these antibodies in the same period, with 40% showing persistent levels despite avoiding gluten.¹⁰

This difference is useful in two ways. First, for NCGS patients, a drop in AGA IgG after starting a gluten-free diet provides some objective confirmation that the diet is working and that the immune system’s reaction to gliadin has subsided. Second, the fact that celiac patients often retain these antibodies longer suggests that the underlying autoimmune process in celiac disease involves deeper tissue damage that takes more time to resolve, or that even small amounts of inadvertent gluten exposure keep the antibodies circulating. For celiac monitoring specifically, tTG IgA is the preferred follow-up marker, but AGA IgG can add information, particularly in the NCGS context where tTG is typically negative to begin with.

Neurological Conditions and Gluten Ataxia

Perhaps the most surprising use of antigliadin antibody testing is in neurology. Gluten ataxia is a condition in which the immune response to gluten damages the cerebellum, the brain region that coordinates movement. People with gluten ataxia may develop unsteady gait, difficulty with fine motor tasks, and balance problems, sometimes without any gastrointestinal symptoms at all. Studies have consistently found a higher prevalence of antigliadin antibodies in patients with gluten sensitivity and neurological dysfunction compared to the general population.¹¹

The challenge is that AGA levels in these patients are often low, sometimes falling below the standard cutoff values used by laboratories. Research on patients with ataxia and low-level AGA found that these individuals still benefited from a strict gluten-free diet, leading the authors to argue that the serological cutoff for AGA needs to be redefined for neurological presentations.¹² In one small study of patients with unexplained sporadic ataxia, IgG AGA was positive in a small percentage, and those patients had positive endomysial antibodies but no celiac changes on duodenal biopsy, fitting the pattern of neurological gluten sensitivity without classic gut involvement.¹³

This is an area where the evidence is still evolving, but the practical takeaway is real: if you have unexplained balance problems or ataxia and your doctor orders an antigliadin antibody test, even a mildly elevated result may be worth pursuing with a trial gluten-free diet, especially when standard celiac tests are negative.

Testing in Young Children

The immune system in very young children is still maturing, which affects how well different antibody tests perform. Standard tTG IgA testing can have suboptimal sensitivity in infants and toddlers, partly because their immune systems haven’t yet mounted the full autoimmune response that produces high tTG levels. Antibodies to deamidated gliadin peptides, particularly IgG anti-DGP, may appear earlier than IgA tTG in very young children with celiac disease, making them a useful early screening tool in this age group.¹⁴

However, the older-style AGA tests measuring antibodies against native (unmodified) gliadin are a different story in pediatrics. Research on children up to two years old found that IgG and IgA antibodies against native gliadin were not helpful for diagnosing celiac disease in this group, with tTG IgA, EMA, and anti-DGP IgG all outperforming them.¹⁵ The difference between native gliadin and deamidated gliadin peptide tests matters even more in pediatrics than it does in adults. If your child’s lab work includes a gliadin antibody, ask whether it was the native or deamidated version.

AGA and Conditions Beyond the Gut

Antigliadin antibodies have been found at elevated rates in several conditions that aren’t traditionally thought of as gluten-related. One of the most studied is schizophrenia. Researchers have noted elevated AGA levels in some patients with schizophrenia, a link that has been postulated for years based on reports of increased gliadin antibodies in this population.¹⁶ The connection doesn’t mean gluten causes schizophrenia, and the antibody pattern in these patients appears to differ from the classic celiac pattern, suggesting a distinct immune response to gliadin rather than the same autoimmune process.

Another association is with latent autoimmune diabetes of adults (LADA), a slow-onset form of autoimmune diabetes sometimes initially mistaken for type 2 diabetes. In a study comparing LADA patients to type 2 diabetes patients, antigliadin antibody rates were significantly higher in the LADA group: about 19% for IgG AGA and 13% for IgA AGA, versus roughly 3.5% for each in the type 2 diabetes group. Endomysial antibody rates, by contrast, were very low in both groups, indicating that most of these gliadin-positive LADA patients did not have full-blown celiac disease.¹⁷ The finding fits a broader pattern in autoimmunity: people with one autoimmune condition tend to produce a wider range of autoantibodies, and antigliadin antibodies may be part of that broader immune dysregulation rather than a sign of celiac disease specifically.

How to Read Your Results

If you’ve had an AGA test and are staring at a lab report, here’s what the different scenarios typically mean:

AGA IgA positive, tTG IgA positive: Strongly suggestive of celiac disease. Your doctor will almost certainly recommend an intestinal biopsy for confirmation.
AGA IgA or IgG positive, tTG negative, EMA negative: Celiac disease is unlikely. The positive AGA could reflect non-celiac gluten sensitivity, a transient immune response, or one of the non-gut-related associations described above. It could also simply be a false positive, given AGA’s lower specificity.
AGA IgG positive with known IgA deficiency: Worth investigating further, especially if IgG tTG is also positive. IgG-based testing is the workaround when your body doesn’t produce enough IgA.
AGA IgG positive with unexplained neurological symptoms: Raises the possibility of gluten ataxia or other neurological gluten sensitivity, even if celiac tests are negative and gut symptoms are absent.
All antibodies negative: Celiac disease and immune-mediated gluten sensitivity are unlikely, though not completely excluded. NCGS can exist with negative serology.

Reference ranges vary between laboratories and between test manufacturers. A result that is borderline or just above the cutoff at one lab might have been negative at another. This is especially relevant for the neurological applications, where research suggests that even low-level positivity may be clinically meaningful.

Antigliadin Antibodies in the Gut’s Compartmentalized Immune System

One of the more intriguing findings about AGA is that your body doesn’t produce them uniformly across all mucosal surfaces. Research comparing IgA antigliadin antibodies in blood, saliva, and intestinal fluid found that the gut and the bloodstream behave as separate immunological compartments. Intestinal IgA AGA levels were elevated in both untreated and treated celiac patients compared to controls, while salivary IgA AGA levels were not elevated at all, and serum IgA AGA was the most diagnostically useful of the three.¹

This compartmentalization means that a blood test is not a perfect window into what’s happening at the gut lining. Treated celiac patients who had adopted a gluten-free diet still showed elevated intestinal AGA even though their serum levels had dropped. The practical implication is that a normalized blood AGA result on a gluten-free diet doesn’t guarantee that the local immune response in the intestine has fully quieted. This is one reason why celiac follow-up often involves periodic biopsy rather than relying on blood markers alone, and why some patients feel ongoing symptoms despite “normal” serology.

For researchers, this compartmentalized response also explains why different body fluids tell different stories about gluten immunity. The saliva, for instance, is immunologically disconnected from the gut’s gliadin response, so salivary tests for AGA have never gained clinical traction despite being less invasive than blood draws. The biology simply doesn’t cooperate.