Randomised clinical study: Gluten challenge induces symptom recurrence in only a minority of patients who meet clinical criteria for non-coeliac gluten sensitivity

Background
It is unknown whether symptoms in non-coeliac patients (non-CD) meeting
clinical diagnostic criteria for noncoeliac gluten sensitivity (NCGS) are
specifically triggered by gluten.
Aim
To assess gluten sensitivity in patients diagnosed with NCGS.
Methods
We studied 35 non-CD subjects (31 females) that were on a gluten-free diet
(GFD), in a double-blind challenge study. Participants were randomised to
receive either gluten-containing flour or gluten-free flour for 10 days, followed
by a 2-week washout period and were then crossed over. The main outcome
measure was their ability to identify which flour contained gluten.
Secondary outcome measures were based upon Gastrointestinal Symptoms
Rating Scale (GSRS) scores.
Results
The gluten-containing flour was correctly identified by 12 participants (34%),
who were classified as having NCGS. Their mean GSRS dimension scores
were significantly higher following gluten challenge compared to baseline.
The scores were: pain, 1.7 0.8 vs. 2.6 1.0; reflux, 1.6 0.5 vs. 2.2 0.9;
indigestion, 1.9 0.7 vs. 3.2 1.1; diarrhoea, 1.6 0.7 vs. 2.9 1.5 and
constipation, 1.9 0.9 vs. 2.9 1.3. Seventeen participants (49%) erroneously
considered the gluten-free flour to contain gluten. Their mean GSRS
dimension scores were significantly higher following gluten-free flour challenge
compared to baseline. The scores were: pain, 1.6 0.9 vs. 3.0 0.9;
reflux, 1.4 0.5 vs. 2.3 1.1; indigestion, 2.0 1.1 vs. 3.7 1.1; diarrhoea,
1.6 0.7 vs. 3.0 1.2 and constipation, 1.6 0.9 vs. 2.6 1.3. The other
six participants (17%) were unable to distinguish between the flours.
Conclusion
Double-blind gluten challenge induces symptom recurrence in just one-third of
patients fulfilling the clinical diagnostic criteria for non-coeliac gluten sensitivity.