Should stored serum of patients previously tested for celiac disease serology be retested for transglutaminase antibodies?

Introduction: Tissue transglutaminase (tTG) antibodies are currently recognized as a highly sensitive indicator of celiac disease (CD). Although a high concordance rate between tTG antibodies and anti-endomysial antibodies (EMA) has been reported up to a third of known CD patients are positive for only one of these antibodies. Aim: To determine whether in laboratories in which serum samples previously examined for CD serology markers had not been discarded, these samples should be tested for tTG antibodies. Methods: Fifty-eight stored (frozen at -70) serum samples of patients previously found to be EMA-negative but positive for one or more of the non-EMA markers: antigliadin antibodies (AGA)-IgA, AGA-IgG, antireticulin antibodies, were tested for anti-tTG antibodies (IMMCO Diagnostics). In patients found to be tTG positive, medical charts were reviewed and patients or their physicians contacted. Results: Twelve of fifty-eight (20.7%) samples were found to be anti-tTG positive. These included: group A: 3/3 samples previously positive for AGA-IgA, AGA-IgG, and antireticulin antibodies. Group 13: 3/16 samples positive for AGA-IgA and AGA-IgG. Group C: 3/4 samples positive for AGA-IgA and group D: 3/35 samples positive for AGA-IgG. Of the 12 positive patients, 1 was a 2-year-old boy, 5 were lost to follow up, and 7 underwent an intestinal biopsy. In 3 of these 7 patients, the biopsy was compatible with CD; 2 of these 3 patients were from group A and I from group B. Conclusions: In laboratories where stored serum samples are available, EMA-negative samples previously found to be positive for at least 2 other CD markers should be retested for tTG antibodies.