Anti-tissue Transglutaminase Antibody Levels Indicate Severity of Villous Abnormalities in Celiac Disease
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Celiac.com 06/06/2014 - Celiac disease guidelines suggest that some patients with high anti-tTG ab levels might be diagnosed without biopsy.
A team of Indian researchers recently reviewed their celiac disease database to determine if anti-tissue transglutaminase (tTG) antibody (ab) titers correlate with severity of villous abnormalities in Indian patients, and to find out a cutoff value of anti-tTG ab fold-rise that might best predict celiac disease. The researchers included P. Singh, L. Kurray, A. Agnihotri, P. Das, A.K. Verma, V. Sreenivas, S. Datta Gupta, and G.K. Makharia. The are affiliated with the Departments of Gastroenterology and Human Nutrition, Pathology, and Biostatistics at the All India Institute of Medical Sciences in New Delhi, India.
The team reviewed data on 366 anti-tTG ab-positive individuals who received duodenal biopsies. The team conducted anti-tTG ab screens before patients began a gluten-free diet, and they expressed anti-tTG ab results in terms of fold-rise by calculating ratio of observed values with cutoff value. Celiac disease was diagnosed only in patients with positive serology, villous atrophy greater than Marsh grade 2, and clear response to gluten-free diet.
Average anti-tTG fold-rise in groups with Marsh grade ≤2 was 2.6 (±2.5), grade 3a was 4.0 (±3.9), 3b was 5.7 (±5.1), and 3c was 11.8 (±8.0). Overall positive likelihood ratio for diagnosing celiac disease was 15.4 and 27.4 at 12- and 14-fold-rise of anti-tTG ab titer, respectively.
The positive predictive value of diagnosis of celiac disease was 100% when anti-tTG ab titer was 14-fold higher over the cutoff value. Fifty-seven (43.9%) patients with anti-tTG titer rise less than 2-fold also had celiac disease. Levels of anti-tTG rise directly with severity of villous abnormality. High anti-tTG ab titers indicate likely villous atrophy.
Contrary to emerging wisdom, even patients with anti-tTG ab levels less than 2-times baseline should receive mucosal biopsies, because many patients with celiac disease have such low levels.
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