Treating coeliac disease. How do we measure adherence to the gluten-free diet?

Abstract

Coeliac disease (CD) is a systemic autoimmune disorder triggered by gluten consumption in genetically susceptible individuals. It exhibits several clinical features, such as blood auto-antibodies (anti-endomysial antibodies EMA, anti-transglutaminase antibodies tTG, anti-deamidated gliadin peptides PGD), plus variable degrees of damage in the small intestinal mucosa. In Chile, tTG is positive in 0.76% in individuals >15 years, with the prevalence of CD being estimated at 0.6%. Approximately17% of first-degree relatives of coeliac patients have been reported tTG positive. To date, the gluten free diet (GFD) is the only known treatment for CD. To be effective, this must be lifelong, permanent, and strict. Gluten content in the GFD is not zero, but is limited to a cut-off of 3 ppm (or mg/kg of product) in Chile. Mortality higher than that of the general population has been reported among coeliac patients, and poor adherence to GFD is associated with complications (mainly autoimmune processes and cancer). GFD is difficult to maintain strictly and poor adherence is by far the main cause of lack of response to treatment. Follow-up of adherence is also difficult because there are no objective measurements to assess it. In clinical practice determination of serum EMA, tTG and PGD is routinely used for these purposes, although more recently, the interview by an expert dietitian, validated questionnaires and measurement of faecal 33-mer peptide are being assessed as alternatives or complements to measure adherence to GFD. A review is presented with the current concepts on the available tools to follow up patients on GFD, emphasising those available in Chilel.