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Comparing urine and stool gluten immunogenic peptides for detecting compliance to gluten-free diets
Konstantinos Gkikas1, Laura Gianolio2, Miles Kavanagh1
1Human Nutrition, School of Medicine, University of Glasgow, New Lister Building, Glasgow Royal Infirmary, Glasgow, UK.
Insights
New point-of-care kits accurately detect gluten immunogenic peptides (GIP) in stool, identifying non-adherence to gluten-free diets (GFD) in children with Crohn's disease. Urine GIP detection was less reliable.
Area of Science:
- Gastroenterology
- Biomarker Development
- Dietary Adherence Monitoring
Background:
- Gluten immunogenic peptides (GIP) are potential biomarkers for monitoring gluten-free diet (GFD) adherence.
- Current GIP detection methods require specialized laboratory facilities and are time-consuming.
- Objective biomarkers are needed to complement subjective dietary assessments.
Purpose of the Study:
- To evaluate novel point-of-care (POC) kits for detecting GIP in stool and urine.
- To assess the utility of POC GIP kits as an objective biomarker for GFD adherence.
- To compare POC GIP detection with reference ELISA methods.
Main Methods:
- Children with Crohn's disease (n=10) and healthy adults (n=17) provided stool and urine samples.
- Samples were collected during and after exclusive enteral nutrition (EEN) and GFD periods.
- Stool GIP was measured using reference ELISA (S-REF) and POC (S-POC) kits; urine GIP using POC (U-POC) kits.
Main Results:
- POC stool GIP detection (S-POC) showed high agreement with reference ELISA (88% concordance, kappa=0.74).
- S-POC identified 8/10 patients as non-adherent to GFD, compared to 2/10 by conventional assessment.
- S-POC demonstrated high sensitivity (100%) and specificity (91%) for GIP detection.
- Urine GIP detection (U-POC) showed lower agreement with S-REF (73% concordance, kappa=0.39).
Conclusions:
- The S-POC kit is a viable, sensitive, and specific alternative for stool GIP detection.
- POC GIP kits can objectively identify GFD non-adherence, potentially improving treatment outcomes.
- Urine GIP detection using POC kits is less accurate and not recommended for monitoring GFD adherence.
Background:
Detection of gluten immunogenic peptides (GIP) is a potential objective biomarker of adherence to gluten-free diet (GFD). As current methods require specialized laboratories, we evaluated novel point-of-care (POC) kits for GIP detection in stool and urine.
Methods:
Ten children with Crohn's disease followed a 3-week GFD, after 8 weeks of exclusive enteral nutrition (EEN). 78 stool and urine samples were collected; one before EEN completion, six during the GFD, and one after return to unrestricted diet. Single samples were collected from 17 healthy adults after a 7-day EEN. Stool GIP was measured with reference ELISA (S-REF) and POC (S-POC) kits; urine GIP with POC kits (U-POC).
Results:
Non-adherence to GFD was detected in 8/10 patients using S-REF, compared to 2/10 patients using conventional dietary assessment. Substantial inter-class agreement was noted between S-REF and S-POC (88% concordance, kappa = 0.74). Lower GIP levels, measured with S-REF, were seen in discordant compared to positive concordant samples. The optimal S-POC detection threshold was 0.11 mg/kg (sensitivity: 100%, specificity: 91%, p < 0.001). Agreement between S-REF and U-POC was lower (concordance: 73%, kappa = 0.39).
Conclusions:
The S-POC kit is a suitable alternative for GIP detection, demonstrating high sensitivity and specificity except at very low GIP levels. Detection of GIP in urine is less accurate.
Impact:
Detection of gluten immunogenic peptides (GIP) offers a promising objective biomarker for monitoring adherence to gluten-free diets. However, current methods require specialized labs and long processing times. By measuring GIP in stool, we identified children with Crohn's disease who were non-adherent despite standard assessments indicating otherwise. A point-of-care GIP kit demonstrated high sensitivity and specificity in detecting GIP in stool making it a potential alternative to the reference ELISA method. In contrast, GIP detection using urine kits was suboptimal. Our study supports the potential clinical utility of bedside point-of-care GIP kits that may improve treatment adherence and efficacy of gluten-free-diets.
