Coeliac disease (1)
A standard gluten challenge consists of the equivalent of 2 serves of gluten containing food (~10 g) per day for up to 8 weeks, followed by serological testing and small bowel biopsy. However, this amount and duration of gluten ingestion is often poorly tolerated, and there has been considerable interest in developing abbreviated challenge protocols to improve adherence without sacrificing diagnostic sensitivity. A recent study by Leffler et al has shown that:
- Over 75% of adults will meet diagnostic criteria for coeliac disease after a 2-week gluten challenge.
- No differences were seen between 3 and 7.5 g of gluten per day suggesting that high doses of gluten exposure are not routinely needed.
- Antibody response in coeliac disease is delayed in comparison with measurable histological changes.
- Coeliac serological titres continue to rise significantly after the end of gluten challenge.
Based on these results, if a patient is already on a gluten free diet at presentation, it is reasonable to recommend the following diagnostic approach:
- perform baseline serology (IgA anti-tTG and IgG anti-gliadin) and HLA DQ2/8 genotyping;
- proceed to small bowel biopsy if serological results are >2x upper limit of normal;
- if not, undertake challenge with 3 g gluten per day (equivalent to ~1½ slices of bread) for 2-3 weeks (or longer if tolerated);
- wait a further 2 weeks after the end of the challenge, then repeat serology and perform small bowel biopsy.