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PTH-192 Once Negative always Negative? – the Clinical Utility of Repeating TTG
  1. S Merson1,
  2. K So1,
  3. R Brown1,
  4. T Ahmad1
  1. 1Royal Devon and Exeter Hospital, Exeter, UK


Introduction Patients with chronic or recurrent abdominal symptoms, or anaemia, often undergo repeated rounds of investigations including tissue transglutaminase (TTG) antibody testing. The aim of this study was to investigate a) the number of patients having multiple TTG tests b) the risk of having a positive TTG after a past negative test.

Methods A list of all TTG requests between 01/01/02–15/07/12 at our laboratory was created. Patients with an initial negative result, but subsequent positive result, were identified, and their hospital and GP records reviewed. Our institution employed the Aesku (Grifols) test prior to 2007 and then the Orgentec test (Launch Diagnostics) and has not used these tests to monitor patients with known Coeliac disease.

Results 44,985 unique patients (65.8%female, 13.5% under 18 years old) had at least one TTG test carried out over the 10.5-year study period. Use of the TTG test has increased (4 new patient tests in 2002 vs. 11,466 in 2011). 2.0% of first TTG tests were positive (2.2% of the total children and 2.0% of the total adults).5,872 patients (69.6% female, 16.6% of the total children and 12.5% of the total adults) had more than 1 test, of which 4,813patients (10.7%) had 2 tests and 1059(2.3%) had 3–10 tests. The median interval between the first and the last test was 21 months (range 1 day - 12.6 yrs). Of the patients with more than one test 17 (7 children), without a prior diagnosis of coeliac disease (CD), had a negative TTG test (whilst taking a normal diet) followed by a positive test. These included 0.7% of the multiply tested children and 0.2% of the multiply tested adults. Reasons for re-testing included persistence or worsening of initial symptoms (53%) or development of new symptoms (76%). There were more women (ratio 3:1). 14/17 (82%) patients had 1 initial negative then a subsequent positive test, with a median time between the tests of 20 months (range 3 – 71 months). 3 (18%) had 2 negative tests then a subsequent positive test with a median time between the first negative test and the positive test of 36 months (range 30 – 41 months). No patients had a positive test after 3 or more negative tests. Of the 17 patients with a negative followed by positive test, 3 had a family history of CD and 2 children had Down’s Syndrome.

Conclusion Clinicians often repeat TTG tests in adults and children when the initial test is negative. The chances of having a positive TTG test after a negative test, even if symptomatic, is low after a median interval of 21 months - in adults this risk is 0.2% and in children 0.7%. In patients with a low pre-test probability of coeliac disease repeat TTG testing following a negative test is not necessary.

Disclosure of Interest None Declared.

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