Introduction
Coeliac disease (CD) guidelines allow biopsy-free diagnosis in children and adults <45 years when levels of IgA anti-tissue transglutaminase antibodies (TG2) exceed ten times the upper limit of normal (>10xULN). This threshold was defined mainly using enzyme-type immunoassays such as ELISA and FEIA. Nowadays, chemiluminescence immunoassays (CLIA) are becoming widespread due to their high analytical throughput, yet they are not explicitly addressed in the guidelines. The >10xULN cut-off may not be directly applicable to these methods.
Aims & Methods
The aims were to establish CLIA-based thresholds for anti-TG2 antibodies with high specificity and positive predictive value (PPV) for CD duodenal atrophy and to evaluate performance differences across age and sex groups. A retrospective observational study was conducted across 3 hospitals in the Vallès Occidental area (Hospital Universitari Mútua de Terrassa, Hospital Universitari Consorci Sanitari de Terrassa, and Consorci Corporació Sanitària Parc Taulí). Patients tested for anti-TG2 antibodies (Catlab laboratory) between 2020 and 2024 were included, provided they had no prior diagnosis of coeliac disease and had undergone a duodenal biopsy while on a gluten-containing diet. Antibody levels were measured using the QUANTA Flash® h-tTG IgA CLIA kit.
Results
203 patients with CD duodenal atrophy were included (n=85 <18 years; 65.5% females): 39 Marsh 3a, 82 Marsh 3b and 82 Marsh 3c with median anti-TG2 antibody levels of 380.0, 758.1, and 1226.8 CU, respectively. The control group included 562 patients (n=50 <18 years; 71.7% females): 285 with normal biopsies, 78 non-coeliac lymphocytic enteritis, 105 potential CD, 90 Marsh 1 CD and 4 non-coeliac atrophy. During the study period, 100 patients were diagnosed according to ESPGHAN 2020 criteria (median anti-TG2 antibody 3145.4 CU; IQR: 921.85-4965.5) (not included for accuracy calculations). The overall cut-off for atrophy, providing a PPV of 99.1% (95% CI: 94.4-100) and a specificity of 99.8% (95% CI: 98.9-100), was 628 CU (31.4xULN), which was similar between children (628 CU) and adults (635.6 CU). The cut-off values differed between men (513.8 CU) and women (379.9 CU) (Table 1). At values above 600 CU, a specificity >99% and a positive predictive value >98% were achieved across all sex and age groups. Fifteen cases were diagnosed by ESPGHAN 2020 criteria with values <600 CU.
Table 1: Sensibility, Specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of the cut-off of TG2 for each study group (95% CI).
Group
| N
| Cut-off
| % Sensibility
| % Specificity
| % PPV
| % NPV
|
Global
| 765
| 628.0
| 54.2 [47.1-61.1]
| 99.8 [98.9-100]
| 99.1 [94.4-100]
| 85.8 [82.8-88.3]
|
Women
| 536
| 379.9
| 66.9 [58.2-74.7]
| 99.3 [97.7-99.8]
| 96.7 [90.1-99.2]
| 90.1 [86.8-92.6]
|
Men
| 229
| 513.8
| 48.6 [36.6-60.7]
| 100 [97.1-100]
| 100 [87.4-100]
| 81.5 [75.2-86.6]
|
<18
| 135
| 628.0
| 41.2 [30.8-52.4]
| 100 [91.1-100]
| 100 [87.7-100]
| 50.0 [40.4-59.6]
|
≥18
| 630
| 635.6
| 63.6 [54.1-72.1]
| 99.8 [98.7-100]
| 98.7 [91.9-99.9]
| 92.2 [89.6-94.3]
|
Conclusion
A cut-off of 600 CU (30xULN) is recommended for CD biopsy-free diagnosis with IgA anti-tissue transglutaminase antibodies measured by QUANTA FLASH® h-tTG IgA chemiluminescence assay. The application of guidelines without considering analysis method can lead to an incorrect prediction of the degree of histological injury.
References
1. Husby S, Koletzko S, Korponay-Szabó IR, et al. European society for pediatric gastroenterology, hepatology, and nutrition guidelines for the diagnosis of coeliac disease. J Pediatr Gastroenterol Nutr. 2012;54(1):136-160. doi:10.1097/MPG.0b013e31821a23d0
2. Husby S, Koletzko S, Korponay-Szabó I, et al. European Society Paediatric Gastroenterology, Hepatology and Nutrition Guidelines for Diagnosing Coeliac Disease 2020. J Pediatr Gastroenterol Nutr. 2020;70(1):141-156. doi:10.1097/MPG.0000000000002497
3. Rubio-Tapia A, Hill ID, Semrad C, et al. American College of Gastroenterology Guidelines Update: Diagnosis and Management of Celiac Disease. Am J Gastroenterol. 2023;118(1):59-76. doi:10.14309/ajg.0000000000002075
4. Al-Toma A, Zingone F, Branchi F, et al. European Society for the Study of Coeliac Disease 2025 Updated Guidelines on the Diagnosis and Management of Coeliac Disease in Adults. Part 1: Diagnostic Approach. United Eur Gastroenterol J. Published online September 2025. doi:10.1002/ueg2.70119
5. Pjetraj D, Pulvirenti A, Moretti M, et al. Diagnostic Accuracy of IgA Anti-Transglutaminase Assessed by Chemiluminescence: A Systematic Review and Meta-Analysis. Nutrients. 2024;16(15). doi:10.3390/nu16152427
