From the Guidelines
A positive Anti-tissue Transglutaminase (Anti-tTGA) IgA test result is highly significant in diagnosing celiac disease, serving as the preferred initial screening test due to its excellent sensitivity and specificity, as supported by the most recent study in 2022 1. This blood test detects antibodies that target the tissue transglutaminase enzyme, which is released during the autoimmune response triggered by gluten consumption in celiac patients. When the test shows elevated Anti-tTGA IgA levels, it strongly suggests celiac disease with high sensitivity and specificity. However, this test should be performed while the patient is on a gluten-containing diet, as following a gluten-free diet can lead to false-negative results, as noted in the 2019 guidelines 1. It's also important to consider IgA deficiency, which can cause false-negative results, and measure total IgA levels simultaneously, as recommended in the 2014 guidelines 1. Some key points to consider in the diagnosis of celiac disease include:
- The patient should be on a gluten-containing diet when the test is performed
- Total IgA levels should be measured to rule out IgA deficiency
- A positive Anti-tTGA IgA test result strongly suggests celiac disease, but definitive diagnosis may require confirmation with duodenal biopsies obtained during endoscopy, especially in adults, as suggested in the 2022 study 1. The combination of positive serology and characteristic histological findings provides the most reliable diagnosis of celiac disease. In clinical practice, the diagnosis of celiac disease should be based on a combination of clinical presentation, serological testing, and histological findings, as supported by the 2019 guidelines 1 and the 2022 study 1. Overall, the Anti-tTGA IgA test is a valuable tool in the diagnosis of celiac disease, and its results should be interpreted in the context of the patient's clinical presentation and other diagnostic findings.
From the Research
Significance of a Positive Anti-tissue Transglutaminase IgA Test Result
A positive Anti-tissue Transglutaminase (Anti-tTGA) Immunoglobulin A (IgA) test result is significant in diagnosing celiac disease. The key points to consider are:
- The sensitivity and specificity of the Anti-tTGA IgA test are high, with values ranging from 90% to 96% and 93% to 98%, respectively 2, 3, 4.
- The test is useful for diagnosing celiac disease in patients with selective IgA deficiency, with IgG anti-tissue transglutaminase antibodies being a reliable alternative 5, 6.
- The test can detect celiac disease in patients with a wide range of clinical manifestations, from asymptomatic to severe enteropathy 2, 3.
Diagnostic Accuracy
The diagnostic accuracy of the Anti-tTGA IgA test is high, with:
- Sensitivity: 90% to 96% 2, 3, 4
- Specificity: 93% to 98% 2, 3, 4
- Positive predictive value: 55% to 98% 3, 4
- Negative predictive value: 87% to 97% 3, 4
Clinical Applications
The Anti-tTGA IgA test has several clinical applications, including: