Published online Mar 21, 2019. doi: 10.3748/wjg.v25.i11.1409
Peer-review started: December 14, 2018
First decision: December 28, 2018
Revised: January 8, 2018
Accepted: January 14, 2019
Article in press: January 14, 2019
Published online: March 21, 2019
Processing time: 96 Days and 12.2 Hours
Until now, there was no objective test to reveal objectively ingested gluten in clinical practice. Recently developed stool and urine laboratory tests based on monoclonal antibody technology specifically determine consumption of gluten by assessing the excretion of gluten immunogenic peptides (GIP). These tests were proposed to help in the monitoring of adherence to the gluten-free diet (GFD). More recently, point-of-care tests (PoCT) for stool and urine have been developed that may encourage patient self-monitoring and better compliance with disease management.
Despite recent research, there are at least three unsolved issues regarding the use of objective tests to detect gluten consumption. (1) The utility of GIP excretion tests, in patients with CeD who consider themselves adherent to the GFD, has not been compared with conventional monitoring methods in a real-life-scenario; (2) It is unknown whether consumption of gluten as measured by GIP excretion is different in symptomatic and asymptomatic CeD patients while on GFD; and (3) It is unclear how the new PoCT tests compare with laboratory-performed GIP tests.
We assessed (1) the performance of enzyme-linked immunosorbent assays (ELISA) and point-of-care (PoCTs) GIP excretion tests in patients with CeD on GFD; and (2) its relation to the presence of symptoms.
We conducted an observational, prospective, cross-sectional study in CeD patients on a GFD for at least two years. Patients were categorized as asymptomatic or symptomatic at enrollment, using the Gastrointestinal Symptom Rating Scale questionnaire. Gluten consumption was assessed by 3-d dietary recall and GIP excretion in stool by ELISA, and by PoCTs in stool and urine using commercial kits.
Forty-four of the sixty-two screened CeD patients were enrolled; nineteen (43.2%) were symptomatic despite being on a GFD. Overall, 83 sets of stool and/or urine samples were collected. At least one positive GIP test was detected in 11 out of the total 44 (25.0%) patients,32% of whom were asymptomatic. GIP was concordant with dietary reports in 65.9% of cases (Cohen´s kappa: 0.317). PoCT tests detected dietary indiscretions. Excretion of GIP was detected in 7(8.4%) stool and/or urine samples from patients considered to be strictly compliant with the GFD by dietary reports.
Our study shows that GIP determination in stool and urine detects dietary transgressions in patients on long-term GFD who are unaware of gluten consumption. Our data also suggest that PoCT for GIP detection in stool and urine constitutes simple home-based methods that may aid in self-assessment of dietary indiscretions, especially inadvertent contaminations.GIP excretion is evident in treated patients, irrespective of the presence of symptoms. This observation confirms that patients should be assessed even when they are asymptomatic and/or have negative serology.
The results support the use of specific GIP tests in stool and urine in conjunction with conventional strategies used to determine adherence to the GFD. One potential future research direction includes the use of these new tools to determine patterns of adherence in patients who believe to be adherent to the GFD. PoCT tests might encourage patients to be involved in self-monitoring and, thus, improve adherence to the diet.