Background: The demand for screening for coeliac disease has grown
rapidly over the last few years. Laboratories depending on immunofluorescence assays
are faced with an increasing workload using a labour-intensive test, and an
alternative to this test has been sought. This study compares tissue transglutaminase
(TTG) and endomysium antibodies (EMA) in a routine clinical laboratory situation.
Methods: An immunofluorescence IgA EMA test was compared with a guinea
pig TTG antibody ELISA for 816 unselected requests for gut antibody screening.
Discrepant results were investigated more fully using a variety of human source TTG
antigen kits.
Results: Guinea pig TTG ELISA and EMA assays showed agreement for 93·6%
of samples. Four samples were misclassified and 48 samples gave false positive TTG
results. Study of 46 EMA samples (this group included 39 of the 'discrepant' negative
EMA/positive guinea pig TTG group) using three different human purified and/or
recombinant TTG sources showed that 42 patients had no TTG antibodies using human
sources, three were misclassified and one patient had negative EMA and positive TTG
results that could not be readily explained. Further study of 32 EMA positive samples
showed almost complete agreement between the human source TTG kits.
Conclusions: We can recommend the replacement of EMA with ELISA for TTG
antibodies for the routine screening for coeliac disease, but all positive TTG
antibodies should still be followed up with IgA EMA and samples should be screened
for IgA deficiency.
