Gluten-Free diet tested as back pain remedy

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: To diagnose IBP the standard Berlin Criteria will be adopted. IBP is defined by at least 2 positive responses among four items: * morning stiffness \>30 min of duration * improvement in back pain with exercise but not with rest * awakening because of back pain during the second half of the night only * alternating buttock pain. To diagnose CD the standard criteria will be adopted. All the patients will meet the following criteria: * positive serum anti-transglutaminase (anti-tTG) and anti-endomysium (EmA) immunoglobulin (Ig)A and IgG antibodies * presence of intestinal villous atrophy. To diagnose NCWS the recently proposed criteria will be adopted. All the patients will meet the following criteria: * negative serum anti-transglutaminase (anti-tTG) and anti-endomysium (EmA) immunoglobulin (Ig)A and IgG antibodies * absence of intestinal villous atrophy * negative IgE-mediated immune-allergy tests to wheat (skin prick tests and/or serum specific IgE detection) * resolution of the IBS symptoms on standard elimination diet, excluding wheat, cow's milk, egg, tomato, chocolate, and other self-reported food(s) causing symptoms * symptom reappearance on double-blind placebo-controlled (DBPC) wheat challenge. As the investigators previously described in other studies, DBPC cow's milk protein challenge and other "open" food challenges will be performed too. Exclusion Criteria: Exclusion criteria for NCWS diagnosis will be: * positive EmA in the culture medium of the duodenal biopsies, also in the case of normal villi/crypts ratio in the duodenal mucosa * self-exclusion of wheat from the diet and refusal to reintroduce it before entering the study * other previously diagnosed gastrointestinal disorders * other previously diagnosed rheumatic diseases * nervous system disease and/or major psychiatric disorder * physical impairment limiting physical activity.