Objectives: False-positive results of anti-tissue-transglutaminase (tTG) IgA autoantibodies have been reported in subjects with a genetic risk for celiac disease (CD). The aims of this retrospective study were to assess the prevalence of false-positive tTG titers in patients at risk of CD compared with symptomatic children and to evaluate the influence of age and indication for testing on tTG titers.
Patients and methods: All tTG results measured in our institution during a 33-month period were evaluated. Patients with known CD were excluded. Indications for testing were either symptoms suggestive of CD (group 1) or history of being at risk for CD (group 2). Duodenal biopsies were recommended if titers were positive (> or =10 U/mL) and offered if borderline (> or =4 to <10 U/mL).
Results: The final analysis included 2056 patients, 1707 belonged to group 1, and 349 to group 2. All 65 patients with positive tTG results underwent biopsy (group 1: 57, group 2: 8). Celiac disease was confirmed in 61 subjects (median titer: 107.8 U/mL, range 12.0-1748 mL, NS between group 1 and 2), whereas 4 had normal histology (10.2-25.2 U/mL). Three out of 16 patients with borderline results underwent biopsy and had normal histology. Borderline titers were more common in group 2 patients (2.6% vs 0.4%, P<0.001). Multiple regression analysis in patients with negative tTG results (n=1975) revealed that titers were independently related to age (P<0.05) and indication for testing (P<0.001).
Conclusions: The influence of age and genetic predisposition/risk has to be taken into account when interpreting tTG results.