Celiac disease is an autoimmune disorder triggered by gluten, a protein found in wheat, barley, and rye. For adults, diagnosing celiac disease accurately is the first step towards managing symptoms and preventing long-term health complications. Many adults live with undiagnosed celiac disease, experiencing a range of symptoms that can be easily mistaken for other conditions. Recognizing the signs and understanding the diagnostic process are crucial for early detection and effective treatment.
Two primary blood tests play a vital role in the initial diagnosis of celiac disease in adults: serology testing and genetic testing.
Serology Testing: Identifying Immune Response
Serology testing is a blood test that looks for specific antibodies in your blood. These antibodies are elevated when your immune system reacts to gluten. In adults, the most common serology tests for celiac disease include:
- Tissue Transglutaminase IgA (tTG-IgA) test: This is usually the first-line serology test for celiac disease. High levels of tTG-IgA antibodies strongly suggest an immune reaction to gluten and are highly indicative of celiac disease.
- Deamidated Gliadin Peptide (DGP IgA and IgG) tests: These tests measure antibodies to deamidated gliadin, another component of gluten. DGP IgA and IgG tests can be particularly useful in individuals with IgA deficiency, a condition where the body doesn’t produce enough IgA antibodies, potentially leading to false negative tTG-IgA results.
- Endomysial Antibody (EMA) test: This test looks for antibodies against endomysium, a connective tissue surrounding muscle fibers. EMA is highly specific for celiac disease, but it is often more expensive and labor-intensive than tTG-IgA.
Elevated levels of these antibodies in adults indicate that their immune system is reacting to gluten, making celiac disease a strong possibility. However, it’s important to note that serology tests are not definitive and further testing is usually required to confirm a Celiac Diagnosis In Adults.
Genetic Testing: Ruling Out Celiac Disease
Genetic testing for human leukocyte antigens (HLA-DQ2 and HLA-DQ8) is another blood test used in the diagnostic process for celiac disease in adults. These genes are present in the vast majority of people with celiac disease.
- HLA-DQ2 and HLA-DQ8 testing: This genetic test identifies whether you carry the HLA-DQ2 and/or HLA-DQ8 genes. While these genes are necessary for developing celiac disease, they are not sufficient on their own. Approximately 30-40% of the general population carries one or both of these genes, but only a small percentage of these individuals will develop celiac disease.
The primary utility of genetic testing in adults is to rule out celiac disease. If you do not have either the HLA-DQ2 or HLA-DQ8 genes, it is highly unlikely you have celiac disease. However, the presence of these genes does not confirm a diagnosis; it simply means you are genetically predisposed to developing the condition. Genetic testing is particularly helpful in certain situations, such as:
- Individuals with negative serology results but high suspicion of celiac disease: In some cases, adults may have celiac disease but test negative on serology tests (e.g., in IgA deficiency or if they have already started a gluten-free diet). Genetic testing can help determine if further investigation is warranted.
- Family members of individuals with celiac disease: Genetic testing can help assess the risk of developing celiac disease in family members of diagnosed individuals.
- Differentiating between celiac disease and non-celiac gluten sensitivity: Genetic testing can sometimes help distinguish between these two conditions, as non-celiac gluten sensitivity is not associated with HLA-DQ2 or HLA-DQ8 genes.
It is critical to undergo testing for celiac disease before starting a gluten-free diet. Eliminating gluten from your diet prior to testing can significantly affect the accuracy of blood tests and subsequent diagnostic procedures, potentially leading to false negative results and delaying a correct diagnosis.
If blood tests suggest celiac disease, further confirmatory testing is typically required. The gold standard for diagnosing celiac disease in adults is an upper endoscopy with biopsies. In some cases, capsule endoscopy may also be used.
Endoscopy: Visual Examination and Biopsy
Endoscopy procedure for celiac disease diagnosis in adults.
An upper gastrointestinal endoscopy is a procedure where a gastroenterologist uses a thin, flexible tube with a light and camera attached (endoscope) to visualize the lining of your upper digestive tract, including the esophagus, stomach, and duodenum (the first part of the small intestine).
During an endoscopy for celiac diagnosis in adults:
- Procedure Details: The endoscope is gently inserted through your mouth and down into your esophagus, stomach, and duodenum. The camera transmits real-time images to a monitor, allowing the doctor to carefully examine the lining of these organs.
- Biopsy Collection: The crucial part of the endoscopy for celiac diagnosis is the collection of multiple small tissue samples (biopsies) from the duodenum. These biopsies are taken even if the lining appears normal to the naked eye, as microscopic damage characteristic of celiac disease may be present even without visible inflammation.
- Villi Damage Assessment: The biopsies are then sent to a pathologist who examines them under a microscope to assess for damage to the villi. Villi are small, finger-like projections that line the small intestine and are responsible for nutrient absorption. In celiac disease, the immune reaction to gluten damages and flattens these villi, leading to malabsorption of nutrients. The pathologist will look for specific changes in the villi, such as villous atrophy (flattening), crypt hyperplasia (increased depth of crypts between villi), and increased intraepithelial lymphocytes (immune cells).
Endoscopy with biopsy is essential for confirming celiac disease in adults because it directly visualizes and assesses the damage to the small intestine, which is the hallmark of the condition. It also helps to rule out other conditions that may cause similar symptoms.
Capsule Endoscopy: Imaging the Small Intestine
Capsule endoscopy, a non-invasive method for celiac disease diagnosis.
Capsule endoscopy is a less invasive procedure that can be used in certain situations to examine the small intestine, especially when a more complete view of the small intestine beyond the duodenum is needed.
In capsule endoscopy for celiac diagnosis in adults:
- Procedure Details: You swallow a small, disposable capsule about the size of a large vitamin pill. This capsule contains a tiny camera, a light source, and a transmitter.
- Image Capture and Transmission: As the capsule naturally travels through your digestive tract, propelled by normal intestinal contractions, the camera takes thousands of images of the lining of your small intestine. These images are wirelessly transmitted to a recorder you wear on a belt around your waist.
- Small Intestine Visualization: Capsule endoscopy provides images of the entire small intestine, which is longer and more difficult to reach with a traditional endoscope.
- Limited Biopsy Capability: A key limitation of capsule endoscopy is that it cannot collect biopsies. Therefore, it is not typically used as the primary diagnostic tool for celiac disease.
Capsule endoscopy may be considered in adults in specific situations, such as:
- When endoscopy results are inconclusive but suspicion remains high: If an upper endoscopy with biopsies is negative or non-diagnostic, but there is still strong clinical suspicion of celiac disease, capsule endoscopy may be used to look for damage further down in the small intestine that might have been missed during a standard endoscopy.
- To evaluate for complications of celiac disease: In adults with known celiac disease who are experiencing persistent symptoms despite a gluten-free diet, capsule endoscopy can be used to investigate for complications such as ulcerative jejunitis (inflammation and ulceration of the jejunum, part of the small intestine) or to rule out other conditions.
Dermatitis Herpetiformis Diagnosis
Dermatitis herpetiformis (DH) is a chronic, intensely itchy skin rash that is another manifestation of celiac disease. For adults presenting with DH, a skin biopsy is often used for diagnosis.
- Skin Biopsy: A small sample of skin is taken from the affected area and examined under a microscope. Specific antibody deposits (IgA) in the skin are characteristic of DH and can confirm the diagnosis.
Adults diagnosed with dermatitis herpetiformis are considered to have celiac disease, even if they do not have typical gastrointestinal symptoms. In these cases, intestinal biopsies are often not required for diagnosis, as the skin biopsy is sufficient.
Further Testing After Celiac Diagnosis
Once celiac disease is diagnosed in adults, additional testing may be recommended to assess for nutritional deficiencies and other complications. This may include blood tests to check levels of:
- Vitamins and Minerals: Vitamins A, B12, D, E, folate, iron, copper, and zinc levels may be checked, as malabsorption due to celiac disease can lead to deficiencies.
- Hemoglobin: To assess for anemia, which can be a complication of celiac disease.
- Liver Enzymes: To evaluate liver function, as liver enzyme abnormalities can sometimes be associated with celiac disease.
- Bone Density Scan (DEXA scan): To check for osteoporosis or osteopenia (reduced bone density), as celiac disease can affect calcium absorption and bone health over time.
These additional tests help to determine the impact of celiac disease on an individual’s overall health and guide appropriate management strategies, including nutritional supplementation if needed.
Conclusion: Taking the Next Steps After Diagnosis
Accurate and timely diagnosis is paramount for adults with celiac disease. If you experience symptoms suggestive of celiac disease, such as chronic diarrhea, abdominal pain, bloating, fatigue, anemia, or unexplained neurological symptoms, it is crucial to discuss these concerns with your doctor. Early diagnosis and adherence to a strict gluten-free diet are essential for managing celiac disease, alleviating symptoms, promoting intestinal healing, and preventing long-term complications. If you are diagnosed with celiac disease, working with a healthcare team, including a registered dietitian, will be vital to successfully navigate a gluten-free lifestyle and maintain optimal health.
