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Tissue transglutaminase antibody levels predict IgA deficiency
  1. A Shahnaz1,
  2. G Maguire2,
  3. R Parker3,
  4. R B Heuschkel1,
  5. M Zilbauer1
  1. 1Department of Paediatric Gastroenterology, Hepatology and Nutrition, Addenbrooke's Hospital, Cambridge University Hospital NHS Trust, Cambridge, UK
  2. 2Department of Biochemistry, Addenbrooke's Hospital, Cambridge University Hospital NHS Trust, Cambridge, UK
  3. 3Department of Public Health and Primary Care, Institute of Public Health, Centre of Applied Medical Statistics, University of Cambridge, Cambridge, UK
  1. Correspondence to Dr Matthias Zilbauer, Department of Paediatric Gastroenterology, Hepatology and Nutrition, Box 267, Addenbrooke's Hospital, Cambridge University Hospital NHS Trust, Hills Road, Cambridge CB2 0QQ, UK; mz304{at}medschl.cam.ac.uk

Abstract

Objective Measuring serum tissue transglutaminase immunoglobulin A (tTG IgA) levels is the most widely used screening test for coeliac disease. However, given an increased prevalence of IgA deficiency among coeliac patients there is a risk of false negative results. Hence, in addition to specific serum tTG IgA, screening tests frequently include total IgA levels. The objective of this study was to determine whether tTG IgA antibody levels might be used to predict IgA deficiency and hence avoid unnecessary testing of total IgA levels in all individuals.

Design Retrospective analysis of 9429 serum tTG IgA and corresponding total IgA levels obtained from children and young adults in the East of England between 2007 and 2011.

Results The overall prevalence of IgA deficiency was found to be very low with only 0.9% of individuals affected. Using receiver operating characteristic curve analysis we identified a cut-off value for tTG IgA of ≥0.10 μ/mL to be predictive for the absence of total IgA deficiency (IgA<0.06 g/L). Specifically, using this cut-off value, total IgA deficiency could be excluded with a sensitivity of 0.92 and specificity of 0.84. In our cohort, only 16.4% of our patient sample would have needed total IgA measurement to rule out a false negative result due to IgA deficiency.

Conclusions Our data provide a simple means of avoiding unnecessary total IgA measurements in the assessment of coeliac disease. By using tTG IgA value quantitatively, only values <0.10 μ/mL require total IgA measurements to rule out IgA deficiency and hence a potentially false negative screening result.

  • Costing
  • Immunology
  • General Paediatrics
  • Gastroenterology

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