Celiac disease is an autoimmune condition where the ingestion of gluten, a protein found in wheat, rye, and barley, triggers an immune response that damages the small intestine. This reaction specifically attacks the villi, the small, finger-like projections lining the intestine responsible for nutrient absorption. Because the disease presents with many non-specific symptoms, misdiagnosis is common. Difficulty in accurate identification can lead to significant delays for patients seeking appropriate care.
Conditions That Present Similarly
The greatest obstacle to a correct diagnosis is that celiac disease shares numerous symptoms with several other common disorders. This overlap often leads physicians to initially diagnose a patient with a more prevalent condition, delaying celiac-specific testing.
Irritable Bowel Syndrome (IBS) is a frequent misdiagnosis, as both conditions cause chronic symptoms like bloating, abdominal pain, diarrhea, and fatigue. Unlike celiac disease, IBS is a functional disorder that does not cause physical damage to the small intestine. Non-Celiac Gluten Sensitivity (NCGS) also mimics celiac disease, causing similar symptoms after consuming gluten, but diagnostic tests for celiac disease are negative. NCGS is not an autoimmune response and does not result in intestinal damage, yet symptomatic relief from a gluten-free diet makes differentiation challenging.
Other inflammatory conditions, such as Crohn’s disease and Ulcerative Colitis (types of Inflammatory Bowel Disease or IBD), share symptoms like diarrhea, anemia, and weight loss. Like celiac disease, IBD involves an immune response that damages the intestinal tract. Additional conditions, including Small Intestinal Bacterial Overgrowth (SIBO), microscopic colitis, and lactose intolerance, can produce similar digestive complaints. Since celiac disease lacks a single, unique symptom, diagnosis requires carefully ruling out these other possibilities.
Common Mistakes in Diagnostic Testing
The most frequent error in the diagnostic pathway is the failure to maintain a full gluten-containing diet throughout testing. The body must be actively reacting to gluten for serology (blood) tests to produce accurate results. Patients must consume an adequate amount of gluten daily, typically for several weeks, before testing. If a patient has already begun a gluten-free diet, low antibody levels can lead to a false negative result. This requirement for a “gluten challenge” is often overlooked, especially when patients have noted symptom improvement.
Another pitfall occurs during the small intestinal biopsy, often considered the gold standard for diagnosis. Errors arise from taking an insufficient number of tissue samples or from poor sample orientation, preventing accurate assessment of villi damage. The characteristic damage, known as villous atrophy, can be patchy, meaning the affected area may be missed if few samples are taken. Misinterpretation of biopsy results can also occur, particularly in cases of mild or early-stage damage.
Over-reliance on genetic testing, which identifies the presence of the HLA-DQ2 or HLA-DQ8 genes, is a third common mistake. While nearly all people with celiac disease carry one of these genes, they are also present in 30 to 40% of the general population without the condition. A positive genetic test indicates only susceptibility and cannot confirm a diagnosis. A negative genetic test is highly effective at ruling out the disease, but a positive result should never be the sole basis for diagnosis.
Health Consequences of Misdiagnosis
An incorrect diagnosis can have distinct health outcomes, depending on whether the diagnosis was a false positive or a false negative. When a patient is incorrectly diagnosed, they are often placed on a gluten-free diet unnecessarily. This diet is socially restrictive and expensive, and if not properly managed, it can lead to deficiencies in nutrients like B vitamins, iron, and fiber.
The failure to diagnose celiac disease (a false negative) allows the autoimmune reaction to continue, leading to chronic damage to the small intestine. This untreated damage prevents proper nutrient absorption, resulting in long-term complications. The delay in treatment caused by a misdiagnosis can lead to irreversible damage and a greater impact on the patient’s long-term health.
Long-Term Complications of Untreated Celiac Disease
- Malnutrition.
- Iron-deficiency anemia and osteoporosis due to poor calcium absorption.
- Increased risk of developing other autoimmune disorders, such as Type 1 diabetes and thyroid disease.
- In rare cases, a type of intestinal cancer called enteropathy-associated T-cell lymphoma.
Ensuring a Definitive Diagnosis
To navigate the diagnostic process correctly, patients should seek a gastroenterologist specializing in celiac disease or complex gastrointestinal disorders. This expertise helps ensure the correct sequence and interpretation of tests are followed, minimizing procedural errors.
The primary protocol requires sequential testing, starting with blood tests to measure specific antibodies, such as tissue transglutaminase IgA (tTG-IgA). A total IgA level must also be measured alongside the antibody test to check for selective IgA deficiency, which could cause a false negative result.
If the blood test suggests celiac disease, the next definitive step is an upper endoscopy with a small bowel biopsy. This procedure allows the gastroenterologist to visually inspect the intestinal lining and collect multiple tissue samples for microscopic examination, confirming villous atrophy. It is paramount that the patient remains on a gluten-containing diet until both the blood tests and the biopsy are completed. Only after receiving a documented diagnosis from a specialist should a patient begin a gluten-free diet.