The study will be a prospective, randomized, placebo-controlled, single center clinical trials. Patients diagnosed with SS, fulfilling the American-European Consensus Group criteria for SS, will be recruited at the outpatient clinic of the Rheumatology Department, University Hospital 'P. Giaccone' of Palermo, Italy.
Inclusion criteria of SS patients
* age \>18 and \<65 years;
* negativity of anti-deamidated gliadin protein (anti-DGP) immunoglobulins (Ig) class A (IgA) and immunoglobulins (Ig)G, anti-tissue transglutaminase (anti-tTG) class IgA and IgG, and Endomysium antibodies (EmA);
* absence of intestinal villous atrophy, documented in all the patients carrying the DQ2 and/or the DQ8 Human Leukocyte Antigen (HLA) haplotypes (thus irrespective of CD-specific serum antibody negativity
* absence of WA (negative prick-test and/or specific serum immunoglobulin (Ig) E assay for wheat, gluten, and gliadin).
Exclusion criteria of SS patients
* age \<18 and \>65 years;
* self-exclusion of gluten/wheat from the diet and refusal to reintroduce it, for diagnostic purposes, before entering the study;
* pregnancy;
* alcohol and/or drug abuse;
* Helicobacter pylori and other bacterial and/or parasitic infections;
* diagnosis of chronic inflammatory bowel disease and other organic pathology affecting the digestive system (e.g., severe liver disease), nervous system diseases, major psychiatric disorders, immunological deficits, and impairments that limit physical activity;
* diagnosis of cancer
* patients undergoing chemotherapy and/or radiotherapy.
Study design In a preliminary phase of the study, all patients who access the SS outpatient clinic of the Rheumatology Department of the University Hospital 'P. Giaccone' of Palermo, Italy, will be asked to answer, consecutively, to a questionnaire for the self-assessment of wheat and other foods' intolerance.
After this evaluation, individual's enrollment will start. A database will be predisposed to register demographic, clinical, laboratory, cytofluorimetric and immunohistochemistry data. A repository bank will be used to collect samples from patients at different timepoints.
Patients enrolled based on the inclusion and exclusion criteria and who have agreed to enter the study, after having signed the informed consent, will be randomized, matched for age/gender/racial origin, through a computerized system into an intervention group and a control group. The two groups, each of 15 subjects, will be asked to follow a diet for 2 months. Intervention group will be asked to eliminate wheat and all cow's milk (both fresh and aged) products from the diet (i.e., WFD plus CMPFD). The control group will be asked to eliminate rice and turkey's meat products from the diet. The elimination diet in the control group must be considered as a 'placebo diet' because both rice and turkey's meat are foods known to be used in standard 'oligoantigenic' elimination diet.
Before starting the elimination diet (at time 0, T0), patients will be evaluated by experienced rheumatologists to assess their clinical features, as well as by physicians with expertise in the field of food intolerance about GI and extraintestinal symptoms which could be related to foods intake. Moreover, at this time point, all subjects will be subjected to:
* salivary flux study, by standard sialometry, and salivary samples collection (treated to block enzymatic digestion of proteins), to dose immunologic and inflammatory markers;
* a blood sample, for the analysis of inflammatory markers, cytokine profile, and intestinal permeability markers;
* a urine collection, after the administration of the lactulose/mannitol (LA/MA) test, to define intestinal permeability;
* a collection of stools, for calprotectin assay and definition of the gut microbiota;
* a dietary consult to better explain the dietary approach and provide any information useful to allow adherence to the elimination diet;
* finally, an alimentary (for the self-assessment of adherence to the diet) and symptom's diary will be provided to all patients, which must be filled-in daily.
After 2 months of elimination diet (at time 1, T1), intervention and control patients will be evaluated again both clinically and by laboratory techniques, repeating exactly what have been done at T0. Moreover, they will have to deliver alimentary and symptom's diary, and will discuss the results with physicians.
At this time-point, the subjects enrolled in the intervention group will go to an open challenge, with reintroduction of wheat. After 2 weeks of open diet or whenever rheumatologic, intestinal and/or extraintestinal symptoms should return or intensify (T2int), patients will be valued again both clinically and by laboratory techniques, repeating exactly what have been done at T0 and T1. Patients in this group will end the study at this time-point.
At the same timepoint, patients enrolled in the control group will be asked to repeat the elimination diet, this time removing from the diet wheat and all cow's milk (both fresh and aged) products (i.e., i.e., WFD plus CMPFD, in the context of a cross-over design), for further 2 months (T2con). At the end of these 2 months patients will be valued again both clinically and by laboratory techniques repeating exactly what have been done at T0 and T1. As described before for the intervention group, at this time-point patients of the control group will go to an open challenge with reintroduction of wheat. After 2 weeks of open diet or whenever rheumatologic, intestinal and/or extraintestinal symptoms should return or intensify (T3con), patients will be valued again both clinically and by laboratory techniques repeating exactly what have been done at T0, T1 and T2con. Patients in this group will end the study at this time-point.
Sample size The sample size is difficult to determine as no precise data are known about the effectiveness of a WFD and the response to wheat re-exposure after challenge in SS patients, as well as NCWS frequency in these subjects; previously reported data suggest that about 25% of NCWS patients suffer from an autoimmune disease, and in a study evaluating the effect of a GFD on quality of life, GI symptoms, and immune system in patients with fibromyalgia and NCWS, statistical significance was reached with 10 subjects. Other studies assessing NCWS immunological pattern obtained statistical significance with 26, 30, 22, and 12 patients. Therefore, considering the nature of this prospective and pilot study the investigators planned to enroll a total of 30 patients suffering from SS, 15 with GI symptoms and 15 without, fulfilling the American-European Consensus Group criteria for SS.
Definition of 'positivity' to the open challenge During the open challenge period, patients will be asked to note the possible onset of intestinal and/or extraintestinal symptoms using the food and symptom's diary, using a 10-point Visual Analogic Scale (VAS). The challenges will be stopped when a clinical reaction will occur for at least two consecutive days with a \>3-point increase in the patient's recorded symptom VAS scale. The challenges will be considered positive if the same symptoms, which were initially present, will reappear after their disappearance on elimination diet and if the GSRS score and/or the extraintestinal symptoms rating scale will be 25% higher than the same score recorded on elimination diet. Finally, from a strictly rheumatologic point of view, the challenge will be considered positive if a 5% increase in the ESSPRI and ESSDAI score will be registered compared to the same score recorded on the elimination diet.
Statistical Analysis Statistical analysis will be performed using commercial software. Parametric and non-parametric statistical analysis will be performed calculating the mean ± standard deviation (SD) and median, respectively. For comparison of parametric and non-parametric data, the t-test and Mann-Whitney rank-sum test will be used where appropriate. Spearman's correlation analysis will be used to quantify the association between analysed variables. Data will be expressed as mean ± SD. P values less than 0.05 will be considered significant.
All subjects will agree to participate in the study. The study protocol will conform to the ethical guidelines of the Declaration of Helsinki, will be preliminary approved by the Human Research committee of the University Hospital of Palermo, Italy, and registered on the CliniaclTrials.gov. All authors will have access to the study data and will review and approve the final manuscript.
