*5.1.2.4 Dietary questionnaires and interviews*

Adherence to GFD can be assessed through dietary interviews or questionnaires conducted by a specialist. Dietitian has an important role in providing practical advice on lifestyle and food choices [16]. Evaluation of adherence to the diet through dietary interviews has been suggested because of its low cost and because it is not invasive; however, they are difficult to standardize and are subjective.

Different questionnaires assess the frequency of food and self-reported adherence to GFD [84]. Some of the more specific questionnaires are—(a) Gluten Free Score by Biagi et al. [85], whose four items provide a score from 0 to IV and in which levels 0 and I indicate poor adherence to the diet and, (b) the Celiac Dietary Adherence Test (CDAT) developed by Leffler et al. [86], which is a brief questionnaire that allows a rapid and standardized evaluation. This last questionnaire comprises seven easy-toapply questions with optimal psychometric characteristics that assess CD symptomatology, self-efficacy expectations, reasons for maintaining GFD, knowledge of the disease, associated risk behaviors, and the perceived degree of adherence.

Nevertheless, there is considerable controversy about the validity of dietary questionnaires in the assessment of GFD because some patients with CD do not record the actual gluten consumed intentionally in some cases. Therefore, the measurement of adherence to GFD through questionnaires appears to be subjective and imprecise and does not allow involuntary infractions to be identified [25, 84].
