Trip Answers

Question answered:30/09/07 Warning! this question is over two years old.

It would appear that gluten in the diet is necessary before carrying out diagnostic tests.  However, it should be noted that all the guidelines we located appear to focus on symptomatic or asymptomatic patients who have included gluten in their diet, and these guidelines emphasise the need for the patient to remain on or to resume a gluten-containing diet whilst autoantibody levels are checked.

 

The NIH Consensus Development Conference on Celiac Disease states:

 

“All diagnostic tests need to be performed while the patient is on a gluten-containing diet. The first step in pursuing a diagnosis of celiac disease is a serologic test. Based on very high sensitivities and specificities, the best available tests are the IgA antihuman tissue transglutaminase (TTG) and IgA endomysial antibody immunofluorescence (EMA) tests that appear to have equivalent diagnostic accuracy (TTG is the specific protein that is identified by the IgA-EMA).  Antigliadin antibody (AGA) tests are no longer routinely recommended because of their lower sensitivity and specificity. Serologic testing for celiac disease in children less than 5 years of age may be less reliable and requires further study.” [1]

 

The North American Society for Paediatric Gastroenterology, Hepatology and Nutrition notes:

 

“There is strong evidence for an increased occurrence of CD in children with dermatitis herpetiformis, dental enamel defects, type 1 diabetes, immunoglobulin A (IgA) deficiency, Down syndrome, Turner syndrome, Williams syndrome, and first-degree relatives of patients with CD.”

 

“It is recommended that testing of asymptomatic children who belong to groups at risk begin around 3 years of age provided they have had an adequate gluten-containing diet for at least 1 year before testing.”

 

“Based on the current evidence and practical considerations, including accuracy, reliability, and cost, measurement of IgA antibody to human recombinant tissue transglutaminase (TTG) is recommended for initial testing for CD.” [2]

 

A third source, the Lab Tests Online website adds:

 

“Autoantibody levels should initially be ordered when a patient still has gluten in their diet. Positive or indeterminate results will then be confirmed with a biopsy.

 

If the person being tested has not consumed any gluten for several weeks prior to testing, then celiac disease tests may be negative (although this may require many months of gluten-free diet). If the doctor still suspects celiac disease, she may do a gluten challenge – have the patient introduce gluten into his diet for several weeks or months to see if the symptoms return…” [3]

 

An e-Medicine article on sprue (celiac disease) offering the following information on pathophysiology:

 

“Celiac disease is an autoimmune disease, and tissue transglutaminase (tTG) has been discovered to be the autoantigen against which the abnormal immune response is directed. Gluten is the single major environmental factor that triggers celiac disease, which has a narrow and highly specific association with class II haplotypes of human leukocyte antigen (HLA) DR17-DQ2 and, to a lesser extent, DR4-DQ8…” [4]

 

References
1. NIH Consens State Sci Statements. 2004 Jun 28-30;21(1):1-23. NIH Consensus Development Conference on Celiac Disease. (http://consensus.nih.gov/2004/2004CeliacDisease118PDF.pdf)
2. Hill, I. D. et al. “Guideline for the diagnosis and treatment of celiac disease in children: recommendations of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition.” Journal of pediatric gastroenterology and nutrition, Jan 05, 40 (1), pgs 1 – 19.
(http://www.guideline.gov/summary/summary.aspx?doc_id=6819&nbr=4186&ss=6&xl=999)
3. Lab Tests Online. Celiac disease. March 2007. (http://www.labtestsonline.org/understanding/analytes/celiac_disease/test.html
4. Busshots N. Sprue. E-Medicine. February 2006. (http://www.emedicine.com/ped/topic2146.htm)
 

---

DISCLAIMER: TRIPanswers is a collection of clinical questions and answers.  Each provider will have their own methodology in answering questions and these are likely not to be as rigorous as systematic review.  If you have any doubt as to the implications of this contact the Q&A Service Provider for further information. This document is presented for information purposes only. This document cannot and should not be used as a basis of diagnosis or choice of treatment, and is in no way intended to replace professional medical care or attention by a qualified practitioner. TRIPanswers and TRIP Database Ltd are not responsible or liable for, directly or indirectly, ANY form of damage whatsoever resulting from the use/misuse of information contained in or implied by this document.  Also, ensure you have read the terms and conditions for using the site.