The use of urine peptidomics to define dietary gluten peptides from patients with celiac disease and the clinical relevance

INTRODUCTION

Determination of urinary gluten immunogenic peptides (GIP) has emerged as one of the most attractive test to monitor the adherence to the gluten-free diet (GFD) of patients with celiac disease (CD), being a simple, noninvasive and direct method to detect gluten contamination of the GFD.

AREAS COVERED

We conducted a scoping review in Medline (PubMed) of articles published up to April 2023 that analyzed any aspect of the clinical relevance of the use of urinary GIP measurement in patients with CD. A total of 17 articles reporting the clinical use of urinary peptidomics for the follow-up of CD patients were finally included.

EXPERT OPINION

Available data suggest that a negative urinary GIP result is a reliable noninvasive predictor of intestinal mucosa healing in CD patients treated with the GFD, especially if testing three urine samples on different days including the weekend. Due to conflicting results about the sensitivity and the specificity of the urinary GIP determination, additional in-depth information is needed, particularly related to (1) the relationship between the amount of ingested gluten and the quantity of urinary GIP excreted in treated CD patients, (2) the GIP kinetics and best timing for sample collection.

Determination of Urinary Gluten Immunogenic Peptides to Assess Adherence to the Gluten-Free Diet: A Randomized, Double-Blind, Controlled Study

INTRODUCTION

The adherence to a gluten-free diet (GFD) is a trending topic in the management of celiac disease. The aim of our study was to evaluate the diagnostic performance of urinary gluten immunogenic peptides (GIP) determination to detect gluten contamination of the GFD.

METHODS

In study A, 25 healthy adults on a standard GFD performed 6 gluten challenges (0, 10, 50, 100, 500, and 1,000 mg) with quantification of urinary GIP before (T0) and during the following 24 hours. In study B, 12 participants on a gluten contamination elimination diet underwent urinary GIP determination at T0 and after challenge with 5 or 10 mg gluten. Urine GIP concentration was determined by an immunochromatographic assay.

RESULTS

In study A, 51 of 150 baseline urine samples were GIP+ on GFD and 7 of 17 were GIP+ after the zero-gluten challenge, whereas only 55 of 81 were GIP+ after the 10-1,000 mg gluten challenges. There was no significant change in the 24-hour urinary GIP when increasing gluten from 10 to 1,000 mg. In study B, 24 of 24 baseline urine samples were GIP-, whereas 8 of 24 were GIP+ after 5 or 10 mg of gluten.

DISCUSSION

Traces of gluten in the standard GFD may cause positivity of urinary GIP determination, whereas a false negativity is common after a gluten intake of 10-1,000 mg. Owing to the impossibility of standardizing the test in normal conditions, it seems unlikely that urinary GIP determination may represent a reliable tool to assess the compliance to the GFD of patients with celiac disease or other gluten-related disorders.

Iodine Absorption in Celiac Children: A Longitudinal Pilot Study

Background: non-autoimmune thyroid disorder is a common finding in celiac patients, more frequent than in the general population. An impairment of iodine absorption has been hypothesized, but it has never been investigated so far. We aimed to evaluate the iodine absorption in children and adolescents with newly diagnosed celiac disease. Methods: 36 consecutive celiac patients (age 7.4 years, range 2.4-14.5 years) before starting a gluten-free diet (GFD) were enrolled. We assayed the urinary iodine concentration (UIC) in a 24-h urine sample, at baseline (T0) after 3 (T1) and 12 months (T2) of GFD. Results: UIC at T0 was 64 μg/L (IQR 45-93.25 μg/L) with an iodine deficiency rate of 77.8%. UIC was not different according to histological damage, clinical presentation (typical vs atypical); we found no correlation with the thyroid function tests and auxological parameters. UIC was not statistically different at T1 (76 μg/L) and T2 (89 μg/L) vs T0. UIC at T2 was similar between patients with positive and negative anti-transglutaminase antibodies at T2. No patients presented overt hypothyroidism during the study. Conclusions: We found that iodine absorption in celiac children is impaired compared to the general population; it increases slightly, but not significantly, during the GFD. We should regularly reinforce the need for a proper iodine intake in celiac disease patients to reduce iodine deficiency risk.

Exposure sources, amounts and time course of gluten ingestion and excretion in patients with coeliac disease on a gluten-free diet

BACKGROUND

A major deficit in understanding and improving treatment in coeliac disease (CD) is the lack of empiric data on real world gluten exposure.

AIMS

To estimate gluten exposure on a gluten-free diet (GFD) using immunoassays for gluten immunogenic peptides (GIP) and to examine relationships among GIP detection, symptoms and suspected gluten exposures METHODS: Adults with biopsy-confirmed CD on a GFD for 24 months were recruited from a population-based inception cohort. Participants kept a diary and collected urine samples for 10 days and stools on days 4-10. 'Doggie bags' containing ¼ portions of foods consumed were saved during the first 7 days. Gluten in food, stool and urine was quantified using A1/G12 ELISA.

RESULTS

Eighteen participants with CD (12 female; age 21-70 years) and three participants on a gluten-containing diet enrolled and completed the study. Twelve out of 18 CD participants had a median 2.1 mg gluten per exposure (range 0.2 to >80 mg). Most exposures were asymptomatic and unsuspected. There was high intra-individual variability in the interval between gluten ingestion and excretion. Participants were generally unable to identify the food.

CONCLUSIONS

Gluten exposure on a GFD is common, intermittent, and usually silent. Excretion kinetics are highly variable among individuals. The amount of gluten varied widely, but was typically in the milligram range, which was 10-100 times less than consumed by those on an unrestricted diet. These findings suggest that a strict GFD is difficult to attain, and specific exposures are difficult to detect due to variable time course of excretion.

Abnormalities in metabolic pathways in celiac disease investigated by the metabolic profiling of small intestinal mucosa, blood plasma and urine by NMR spectroscopy

Celiac disease (CeD) is an autoimmune enteropathy caused by gluten intake in genetically predisposed individuals. We investigated the metabolism of CeD by metabolic profiling of intestinal mucosa, blood plasma and urine using NMR spectroscopy and multivariate analysis. The metabolic profile of the small intestinal mucosa was compared between patients with CeD (n = 64) and disease controls (DCs, n = 30). The blood plasma and urinary metabolomes of CeD patients were compared with healthy controls (HCs, n = 39). Twelve metabolites (proline (Pro), arginine (Arg), glycine (Gly), histidine (His), glutamate (Glu), aspartate, tryptophan (Trp), fumarate, formate, succinate (Succ), glycerophosphocholine (GPC) and allantoin (Alln)) of intestinal mucosa differentiated CeD from controls. The metabolome of blood plasma with 18 metabolites (Pro, Arg, Gly, alanine, Glu, glutamine, glucose (Glc), lactate (Lac), acetate (Ace), acetoacetate (AcAc), β-hydroxybutyrate (β-OHB), pyruvate (Pyr), Succ, citrate (Cit), choline (Cho), creatine (Cr), phosphocreatine (PCr) and creatinine) and 9 metabolites of urine (Pro, Trp, β-OHB, Pyr, Succ, N-methylnicotinamide (NMN), aminohippurate (AHA), indoxyl sulfate (IS) and Alln) distinguished CeD from HCs. Our data demonstrated changes in nine metabolic pathways. The altered metabolites were associated with increased oxidative stress (Alln), impaired healing and repair mechanisms (Pro, Arg), compromised anti-inflammatory and cytoprotective processes (Gly, His, NMN), altered energy metabolism (Glc, Lac, β-OHB, Ace, AcAc, Pyr, Succ, Cit, Cho, Cr and PCr), impaired membrane metabolism (GPC and Cho) and intestinal dysbiosis (AHA and IS). An orthogonal partial least square discriminant analysis model provided clear differentiation between patients with CeD and controls in all three specimens. A classification model built by combining the distinguishing metabolites of blood plasma and urine samples gave an AUC of 0.99 with 97.7% sensitivity, 93.3% specificity and a predictive accuracy of 95.1%, which was higher than for the models built separately using small intestinal mucosa, blood plasma and urine. In conclusion, a panel of metabolic biomarkers in intestinal biopsies, plasma and urine samples has potential to differentiate CeD from controls and may complement traditional tests to improve the diagnosis of CeD.

The Profile of Urinary Headspace Volatile Organic Compounds After 12-Week Intake of Oligofructose-Enriched Inulin by Children and Adolescents with Celiac Disease on a Gluten-Free Diet: Results of a Pilot, Randomized, Placebo-Controlled Clinical Trial

The concentration of volatile organic compounds (VOCs) can inform about the metabolic condition of the body. In the small intestine of untreated persons with celiac disease (CD), chronic inflammation can occur, leading to nutritional deficiencies, and consequently to functional impairments of the whole body. Metabolomic studies showed differences in the profile of VOCs in biological fluids of patients with CD in comparison to healthy persons; however, there is scarce quantitative and nutritional intervention information. The aim of this study was to evaluate the effect of the supplementation of a gluten-free diet (GFD) with prebiotic oligofructose-enriched inulin (Synergy 1) on the concentration of VOCs in the urine of children and adolescents with CD. Twenty-three participants were randomized to the group receiving Synergy 1 (10 g per day) or placebo for 12 weeks. Urinary VOCs were analyzed using solid-phase microextraction and gas chromatography⁻mass spectrometry. Sixteen compounds were identified and quantified in urine samples. The supplementation of GFD with Synergy 1 resulted in an average concentration drop (36%) of benzaldehyde in urine samples. In summary, Synergy 1, applied as a supplement of GFD for 12 weeks had a moderate impact on the VOC concentrations in the urine of children with CD.

Gluten immunogenic peptide excretion detects dietary transgressions in treated celiac disease patients

BACKGROUND

Life-long removal of gluten from the diet is currently the only way to manage celiac disease (CeD). Until now, no objective test has proven useful to objectively detect ingested gluten in clinical practice. Recently, tests that determine consumption of gluten by assessing excretion of gluten immunogenic peptides (GIP) in stool and urine have been developed. Their utility, in comparison with conventional dietary and analytical follow-up strategies, has not been fully established.

AIM

To assess the performance of enzyme-linked immunosorbent assay (ELISA) and point-of-care tests (PoCTs) for GIP excretion in CeD patients on gluten-free diet (GFD).

METHODS

We conducted an observational, prospective, cross-sectional study in patients following a GFD for at least two years. Using the Gastrointestinal Symptom Rating Scale questionnaire, patients were classified at enrollment as asymptomatic or symptomatic. Gluten consumption was assessed twice by 3-d dietary recall and GIP excretion (by ELISA in stool and PoCTs (commercial kits for stool and urine) in two consecutive samples. These samples and dietary reports were obtained 10 day apart one from the other. Patients were encouraged to follow their usual GFD during the study period.

RESULTS

Forty-four patients were enrolled, of which 19 (43.2%) were symptomatic despite being on a GFD. Overall, 83 sets of stool and/or urine samples were collected. Eleven out of 44 patients (25.0%) had at least one positive GIP test. The occurrence of at least one positive test was 32% in asymptomatic patients compared with 15.8% in symptomatic patients. GIP was concordant with dietary reports in 65.9% of cases (Cohen´s kappa: 0.317). PoCT detected dietary indiscretions. Both ELISA and PoCT in stool were concordant (concomitantly positive or negative) in 67 out of 74 (90.5%) samples. 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.

CONCLUSION

GIP detects dietary transgressions in patients on long-term GFD, irrespective of the presence of symptoms. PoCT for GIP detection constitutes a simple home-based method for self-assessment of dietary indiscretions.

Are Treated Celiac Patients at Risk for Mycotoxins? An Italian Case-Study

Urinary biomarkers of mycotoxin exposure were evaluated in a group of celiac patients (n = 55) and in a control group of healthy subjects (n = 50) following their habitual diet. Deoxynivalenol (DON), zearalenone (ZEN), and fumonisin B1 (FB1) were monitored in 105 urinary samples collected from the two groups. Dietary habits were also recorded through compilation of a seven-day weighed dietary diary. Biomarkers of mycotoxin exposure were detected in 21 celiac patients and in 15 control subjects, corresponding to about 34% of total participants. In particular, ZEN was the most detected mycotoxin among all the studied subjects with a total of 19 positive cases. Results did not show a statistically significant difference in mycotoxin exposure between the two groups, and the presence of specific mycotoxins was not related to the intake of any particular food category. Our findings suggest little urgency of specific regulation for gluten free products, although the prevalence of exposure observed in free-living diets of both celiac and healthy subjects underlines the need of a constant surveillance on mycotoxins occurrence at large.

The urinary inflammatory profile in gluten free diet-adherent adolescents with type 1 diabetes and celiac disease

AIMS

Our objective was to characterize urinary cytokine/chemokine excretion in adolescents with type 1 diabetes (T1D) and celiac disease (CD) adhering to gluten free diet (GFD) compared to matched T1D patients and healthy control (HC) group from an existing cohort.

METHODS

Eighteen T1D+CD+GFD patients aged 10-16years were identified and matched 2:1 for age, sex, diabetes duration and glycated hemoglobin to 36 T1D subjects and 36 HC. T1D+CD+GFD patients were adherent with a GFD. Urine and serum levels of cytokines/chemokines as well as baseline clinical and laboratory variables were assessed.

RESULTS

T1D+CD+GFD patients exhibited lower levels of urinary IL-1B, IL-4, IL-5 (p<0.05) and IFN-γ, IL-8 and G-CSF levels (p<0.07) compared with T1D patients. Urinary biomarker levels between T1D+CD+GFD and HC were mostly similar. In contrast, urinary FGF-2, Flt-3, IL-1B, IL-1RA, IL-4, IL-5, IL-9, IL-10, IL-12p40, IL-15, MIP-1β, and TNF-β (p<0.05) were higher in T1D patients compared to HC. Similar levels of inflammatory markers were seen in the serum for all 3 groups.

CONCLUSIONS

T1D+CD+GFD patients demonstrated decreased urinary inflammatory cytokine/chemokines compared to T1D and some similar to HC, which is suggestive of a potential modulatory role of treated CD on urinary markers.

Urinary polyaromatic hydrocarbons are associated with adult celiac disease and kidney stones: USA NHANES, 2011-2012

Links between environmental chemicals and human health have emerged over the last few decades, but the effects from polyaromatic hydrocarbons (PAH) were less studied, compared to other commonly known environmental chemicals such as heavy metals, phthalates, arsenic, phenols, and pesticides. Therefore, it was aimed to study the relationships of urinary PAH and adult digestive conditions using a large human sample in a national and population-based study in recent years. Data was retrieved from the US National Health and Nutrition Examination Surveys, 2011-2012 including demographics, self-reported health conditions, and urinary PAH. Statistical analyses included chi-square test, t test, survey-weighted logistic regression modeling, and population attributable risk (PAR) estimation. Of 5560 American adults aged 20-80 and included in the statistical analysis, urinary 4-hydroxyphenanthrene was significantly associated with celiac disease (odds ratio (OR) 1.61, 95% confidence interval (CI) 1.14-2.26, P = 0.009). In addition, urinary 2-hydroxyfluorene (OR 1.35, 95% CI 1.02-1.78, P = 0.038), 3-hydroxyfluorene (OR 1.35, 95% CI 1.07-1.70, P = 0.015), 1-hydroxyphenanthrene (OR 1.48, 95% CI 1.08-2.03, P = 0.017), 1-hydroxypyrene (OR 1.36, 95% CI 1.05-1.77, P = 0.023), and 2-hydroxynapthalene (OR 1.25, 95% CI 1.00-1.58, P = 0.054) were significantly associated with kidney stones, although not necessarily failing kidney. There were no statistically significant associations observed in the relationship of urinary PAH and liver problems, although higher levels of PAHs were observed. Urinary PAHs are associated with adult digestive conditions, although the causality cannot be established. From the research perspective, longitudinal monitoring from observational studies and experimental research understanding mechanism would be suggested. Regulation of minimizing PAHs exposure might need to be considered in future health and environmental policies.

Differentiating coeliac disease from irritable bowel syndrome by urinary volatile organic compound analysis--a pilot study

Coeliac disease (CD), a T-cell-mediated gluten sensitive enteropathy, affects ∼ 1% of the UK population and can present with wide ranging clinical features, often being mistaken for Irritable Bowel Syndrome (IBS). Heightened clinical awareness and serological screening identifies those with potential coeliac disease; the diagnosis is confirmed with duodenal biopsies, and symptom improvement with a gluten-free diet. Limitations to diagnosis are false negative serology and reluctance to undergo biopsy. The gut microbiome is altered in several gastrointestinal disorders, causing altered gut fermentation patterns recognisable by volatile organic compounds (VOC) analysis in urine, breath and faeces. We aimed to determine if CD alters the urinary VOC pattern, distinguishing it from IBS. 47 patients were recruited, 27 with established CD, on gluten free diets, and 20 with diarrhoea-predominant IBS (D-IBS). Collected urine was stored frozen in 10 ml aliquots. For assay, the specimens were heated to 40 ± 0.1°C and the headspace analysed by Field Asymmetric Ion Mobility Spectrometry (FAIMS). Machine learning algorithms were used for statistical evaluation. Samples were also analysed using Gas chromatography and mass spectroscopy (GC-MS). Sparse logistic regression showed that FAIMS distinguishes VOCs in CD vs D-IBS with ROC curve AUC of 0.91 (0.83-0.99), sensitivity and specificity of 85% respectively. GCMS showed a unique peak at 4'67 found only in CD, not D-IBS, which correlated with the compound 1,3,5,7 cyclooctatetraene. This study suggests that FAIMS offers a novel, non-invasive approach to identify those with possible CD, and distinguishes from D-IBS. It offers the potential for monitoring compliance with a gluten-free diet at home. The presence of cyclooctatetraene in CD specimens will need further validation.

Children with screening-detected coeliac disease show increased levels of nitric oxide products in urine

AIM

Increased concentration of nitric oxide (NO) metabolites, nitrite and nitrate, in the urine is a strong indication of ongoing small intestinal inflammation, which is a hallmark of the enteropathy of coeliac disease (CD). It has previously been shown that children with symptomatic, untreated CD have increased levels of NO oxidation products in their urine. The aim of this study was to investigate whether screening-detected, asymptomatic coeliac children display the same urinary nitrite/nitrate pattern.

METHODS

In a multicenter screening study, serum samples were collected from 7208 12-year-old children without previously diagnosed CD. Sera were analysed for anti-human tissue transglutaminase (tTG) of isotype IgA. Small bowel biopsy was performed in antibody-positive children, yielding 153 new cases of CD. In the screening-detected individuals, the sum of nitrite and nitrate concentrations in the urine was analysed and used as an indicator of NO production. For comparison, 73 children with untreated, symptomatic CD were studied.

RESULTS

The nitrite/nitrate levels in children with screening-detected CD and those with untreated symptomatic CD did not differ significantly. Both groups had significantly increased urinary nitrite/nitrate concentrations compared to the children with normal small bowel biopsy (p < 0.001).

CONCLUSION

  Children with screening-detected CD have increased production of NO just as children with untreated symptomatic CD. High NO metabolite levels in the urine may indicate a pathogenetic feature of CD and be a marker of major clinical importance.

Serum copper, ceruloplasmin and 24-h urine copper evaluations in celiac patients

The aim of the study is to evaluate the serum copper, ceruloplasmin and 24-h urine copper levels in celiac patients. Serum copper, ceruloplasmin and 24-h urine measurements were evaluated in patients with celiac (n = 32), Crohn's (n = 25), Wilson's (n = 11) and in a healthy group (n = 35). Serum and 24-h urine zinc levels, AST, ALT, BUN, creatinine, iron, hemoglobin, hematocrit, lymphocyte, sedimentation and CRP levels were also measured. Results were evaluated statistically and significance was accepted as meaningful if P < 0.05. In celiacs, levels of urine copper were high (52 +/- 29 microg/day, P < 0.000) but serum copper was the same as in controls (105 +/- 16 microg/dl, P < 0.158). High urinary copper of celiacs were coming out in women (56 +/- 30 microg/day) and in man (33 +/- 17 microg/day, P < 0.115). Most celiacs were female (P < 0.001). Serum copper and ceruloplasmin levels in all groups were higher in women than in men and this was meaningful for serum copper in the control group (P < 0.045) and for ceruloplasmin in Crohn's (P < 0.055) and control groups (P < 0.031). Serum (70 +/- 14 microg/dl, P < 0.000) and urine zinc levels (25 +/- 15 microg/dl, P < 0.039) of celiacs were low. Ceruloplasmin levels were higher in celiacs (337 +/- 64 U/1) and Crohn's patients (366 +/- 47 U/l, P < 0.000). Correlations observed in the groups of celiac (P < 0.029) and Crohn's (P < 0.024), celiac and Wilson's (P < 0.001) and Crohn's and Wilson's (P < 0.001) between the ceruloplasmin and 24-h urine copper parameters. AST and ALT levels were higher in celiac and Wilson's patients than in Crohn's patients and controls. Mean CRP levels were significantly higher in Crohn's than others. Lymphocyte counts were meaningfully higher in celiacs. Statistically, while mean iron, hemoglobulin and hematocrit levels of celiac and Crohn groups were meaningfully lower than the normal and Wilson's group, it was similar in Wilson's and the control group. Serum copper (85 +/- 26 microg/dl, P < 0.158) and ceruloplasmin (219 +/- 83 U/l, P < 0.001) levels were low and 24-h urine copper levels were high (415 +/- 346 microg/day) in Wilson's group. Increased urinary loss may be another cause of copper deficiency in female celiacs besides malabsorption and this topic needs more investigation. Increased urinary copper levels in celiac women should not always be regarded as a diagnosis of Wilson's disease.

Intestinal permeability and antigliadin antibody test for monitoring adult patients with celiac disease

Celiac disease causes chronic inflammation of the intestinal mucosa and reduces surface absorption; after the withdrawal of gluten from the diet, there are clinical and histologic improvements. The intestinal permeability test and serologic tests are useful for confirming the diagnosis and monitoring patients. The goal of this study is to compare the antigliadin antibody (AGA) test with the intestinal permeability test for celiac patients on a gluten-free diet. The sample consisted of 22 celiac patients who were antigliadin immunoglobulin A-positive before treatment. After 12 months on a gluten-free diet, AGA testing was repeated and the intestinal permeability test was performed. A control group was composed of 11 healthy individuals. AGA remained positive in 40.9% of celiac patients, and the mean urinary lactulose excretion was 10.27%, that of mannitol was 10.18%, and the lactulose/mannitol ratio was 1.02. In the subgroup in which antigliadin became negative (59.1%), the value for lactulose was 3.79%, that for mannitol was 11.12%, the lactulose/mannitol ratio was 0.38, and the p value was less than 0.0001, 0.66, and less than 0.0001, respectively. When the two celiac subgroups were compared with the control group, the urinary lactulose excretion and the lactulose/mannitol ratio was less in the control group, whereas urinary mannitol excretion was greater. The p values were less than 0.0001 for the three variables, suggesting persistent lesions in mucosa of both subgroups, although to a lesser degree for those that became AGA negative. It is concluded that intestinal permeability allows a more precise clinical physiopathologic correlation than antigliadin and offers more information for the monitoring of these patients.

Urinary nitric oxide during one year of gluten-free diet with or without oats in children with coeliac disease

OBJECTIVE

Although in both adults and children with coeliac disease (CD) it is now recommended that oats be added to their gluten-free diet, there is still some controversy concerning the possible harmful effects of oats in some individuals. In this study concentrations of nitric oxide metabolites were repeatedly measured in the urine of children under investigation for CD, when on a gluten-free diet with or without oats.

MATERIAL AND METHODS

The study included 116 children, randomized to a standard gluten-free diet (GFD-std) or a gluten-free diet supplemented with wheat-free oat products (GFD-oats), over a one-year period. Small-bowel biopsy was performed at the beginning and end of the study. Morning urine samples were collected from 87 children and urinary nitrite/nitrate concentrations were monitored at 0, 3, 6, 9 and 12 months.

RESULTS

All patients were in clinical remission after the study period. There was a rapid decline in urinary nitrite/nitrate concentrations in both groups as early as after 3 months. No differences were seen between the study groups at any of the checkpoints. However, at the end of the study, the nitrite/nitrate values of 9 children in the GFD-oats group and 8 children in the GFD-std group had not normalized.

CONCLUSIONS

Children with CD on a gluten-free diet with oats display a similar reduction in urinary nitrite/nitrate as those on a traditional gluten-free diet. Some children, however, still demonstrate high nitrite/nitrate excretion after one year on either diet, indicating that long-term follow-up studies of children on an oats-containing diet are needed.

Simultaneous gas-chromatographic measurement of rhamnose, lactulose and sucrose and their application in the testing gastrointestinal permeability

BACKGROUND

As it is important to test gastric and intestinal permeability simultaneously in gastrointestinal disorders such as Celiac disease, we developed a gas-chromatographic (GC) method to estimate rhamnose (L-rh), lactulose (Lacl) and sucrose (Suc) in urine.

METHODS

The method is based on the use of alditol acetate derivatives giving a lower number of GC peaks than reducing sugars do. Acetate derivatives are more stable and less expensive than GC silylates and keep the flame-detector cleaner. We checked the chemical stability of alditol acetates by verifying the reproducibility of the standard curve of a sugar derivative sample which had been stored for 2 months at -20 degrees C.

RESULTS

The calibration proved linear over the range 0.1-1 microg of sugar injected. Analytical sugar recovery was 88%+/-19.4% (mean+/-S.D.) for rhamnose, 105%+/-7.4% for sucrose and 102%+/-2.4% for lactulose. Mean within-day precision (CV) was 7.7% for rhamnose, 5.7% for sucrose and 1.9% for lactulose, and between-day (CV) was 6.7% for rhamnose, 3.9% for sucrose and 1.6% for lactulose. The rhamnose, lactulose and sucrose as the lactulose/rhamnose ratio clearly differentiated 25 healthy controls from 36 patients with active gluten-sensitive enteropathy.

CONCLUSIONS

A fast, reliable and cheap gas-chromatographic method is presented here to evaluate gastric and intestinal permeability.

Urinary NOx:creatinine ratios during gluten challenge in children with celiac disease

OBJECTIVES

Celiac disease is a gluten-induced small bowel enteropathy. Inflammation is known to be associated with enhanced nitric oxide (NO) production. An increase in urinary nitrate and nitrite (NOx) reflects increased NO production. The urinary NOx:creatinine ratio can be used as an indicator of the endogenous NO production. The aim of the study was to determine whether the urinary NOx:creatinine ratio of celiac disease patients increases during gluten challenge.

METHODS

The authors studied 20 patients with unconfirmed celiac disease who had been following a gluten-free diet for at least 1 year. These patients underwent an 80-day gluten challenge. Urinary samples were obtained before and 10, 20, 40, and 80 days after starting the gluten challenge. The Griess reagent method was used for measuring urinary NOx.

RESULTS

Gluten challenge confirmed the diagnosis of celiac disease in 15 of 20 patients. The NOx:creatinine ratios (mmol:mmol) of the biopsy-confirmed celiac disease patients were significantly higher than those of the unconfirmed celiac disease patients (0.67 vs. 0.17 on day 10; 0.78 vs. 0.15 on day 20; 0.85 vs. 0.25 on day 40; and 0.85 vs. 0.17 on day 80).

CONCLUSIONS

Gluten challenge resulted in an increased urinary NOx:creatinine ratio in patients with biopsy-confirmed celiac disease. The NOx:creatinine ratio could be useful for the serial evaluation of disease activity.

Increase in nitric oxide urinary products during gluten challenge in children with coeliac disease

BACKGROUND

Coeliac disease is a gluten-sensitive enteropathy where pro-inflammatory cytokines and excess nitric oxide (NO) production can contribute to mucosal damage. NO urinary products are elevated in coeliac children on a gluten diet, but it is not known how rapidly this increase develops after gluten exposure.

METHODS

Oral gluten challenge was performed in 25 children whose families kept a daily record of gluten intake and symptoms. Blood was analysed monthly for antigliadin (AGA) and endomysium antibodies (EMA). Urine was analysed every second week for NO products, i.e. the sum of nitrite and nitrate was measured with a colorimetric method. We performed a third biopsy when clinical symptoms indicated a relapse. Median age at the post-challenge biopsy was 3.8 (2.7-8.8) years.

RESULTS

Signs of morphological or serological relapse were seen in all children. Mean daily gluten intake was 0.10 (range 0.02-0.26) g/kg bodyweight. Median NO level was doubled and significantly higher after 4 weeks of challenge but not after 2 weeks. EMA, but not AGA levels, correlated positively with NO. Intraepithelial lymphocyte count was significantly higher in the post-challenge biopsy, but did not correlate with the NO levels.

CONCLUSIONS

NO products in urine increased during gluten challenge. EMA levels reflected severity of mucosal damage, and NO products reflected the inflammatory response, which was doubled after 4 weeks of challenge. The NO analysis is simple and non-traumatic for the child. It can be performed repeatedly during investigation of children with suspected coeliac disease.

Conjugated bile acid replacement therapy reduces urinary oxalate excretion in short bowel syndrome

BACKGROUND

Patients with short bowel syndrome (SBS) have steatorrhea, in part because of bile acid malabsorption that causes decreased bile acid secretion into the duodenum and consequent fat maldigestion. In SBS patients with colon in continuity, luminal calcium forms calcium fatty acid soaps rather than precipitating as insoluble calcium oxalate. Soluble oxalate is hyperabsorbed by the colon leading to hyperoxaluria and an increased risk for renal calcium oxalate stones and deposits. The authors hypothesized that oral ingestion of conjugated bile acids would increase fat absorption and thereby decrease calcium fatty acid soap formation and oxalate hyperabsorption.

METHODS

The effect of conjugated bile acid replacement therapy (9 g/d) on fecal fat excretion and urine oxalate excretion was measured in an appropriate patient, utilizing the metabolic balance technique. The effects of chronic bile acid replacement therapy on oxalate excretion and nutritional status also were measured in a 3-month outpatient study.

RESULTS

Natural conjugated bile acid replacement therapy reduced fecal fat excretion from 119 to 79 g/d (Delta40 g/d), and urinary oxalate excretion from 87 to 64 mg/d (966 to 710 micromol/d; Delta23 mg/d). Cholylsarcosine, a synthetic conjugated bile acid, had similar but less powerful effects. During a 3-month outpatient trial of natural conjugated bile acids (9 g/d), urine oxalate decreased to normal levels (27 mg/d) in association with weight gain, decreased hunger, and decreased hyperphagia.

CONCLUSION

Conjugated bile acid replacement therapy reduced fecal fat excretion, reduced urinary oxalate excretion, and improved nutritional status in a patient with SBS with colon in continuity, hyperoxaluria, and oxalate nephrolithiasis.

Lactulose-mannitol intestinal permeability test: a useful screening test for adult coeliac disease

The aim of this study was to determine the value of the lactulose mannitol intestinal permeability test in screening the general adult population for unrecognized enteropathy and latent coeliac disease. Subjects with positive serology (identified by screening carried out by the Belfast MONICA Project) along with controls were followed-up after 3 years and classified as having transient serology, persistent serology or coeliac disease. A 5-h urine collection was performed following the ingestion of 5 g lactulose, 2 g mannitol and glucose as an osmotic filler. Urinary concentrations of lactulose and mannitol were measured by enzymatic analysis. Percentage lactulose excretion (%LE) (0.94 versus 0.31, P<0.001) and lactulose mannitol excretion ratio (LMER) (0.12 versus 0.02, P<0.001) were significantly higher in screening-detected coeliac disease subjects compared with MONICA controls. The sensitivity of the permeability test was 87% in the screening situation compared with 81% in the clinical situation. In subjects with persistent and transient serology the LMER did not differ significantly from that of controls. The lactulose-mannitol test is a useful test for screening the general adult population for coeliac disease. Subjects with persistent and transient serology did not differ from MONICA controls and are unlikely to have latent coeliac disease.

Sensitivity of a hyperosmolar or "low"-osmolar test solution for sugar absorption in recognizing small intestinal mucosal damage in coeliac disease

Reliability of differential sugar absorption tests is hampered by a lack of standardization of the content and osmolarity of the test solutions. We evaluated the effect of osmolarity of the test solution of the sugar absorption test on the 5 hour urine excretion of orally administered lactulose and mannitol. A group of 28 controls and 14 coeliacs, with villous atrophy grade II to IV, ingested a hyperosmolar sugar absorption test solution and a "low"-osmolar solution, respectively. After an overnight fast, each subject ingested hyperosmolar sugar absorption test solution (2 g mannitol, 5 g lactulose and 40 g sucrose/100 ml (around 1,560 mmol/l)). After two days, this procedure was repeated with low-osmolar solution (2 g mannitol and 5 g lactulose/100 ml (around 375 mmol/l). The influence of the sequence of the tests on the results had previously been excluded. All urine from the 5 h-period following ingestion of the test solution was collected. To calculate the low-osmolar solution ratio, samples were analysed for lactulose and mannitol concentrations by gas chromatography The sensitivity of hyperosmolar SAT solution and low-osmolar solution for the detection of mucosal abnormalities in coeliacs was 64% and 43%, respectively. In conclusion, a hyperosmolar solution discriminates better between normal and damaged mucosa of the small bowel such as villous atrophy due to a relative increase in permeability for lactulose.

The caffeine metabolic ratio as an index of xanthine oxidase activity in clinically active and silent celiac patients

BACKGROUND

The xanthine oxidoreductase system has been identified as one of the main sources of free radicals responsible for various forms of tissue injury. Because the intestinal villi are an important location of this enzyme, it was of interest to study the role of xanthine oxidase in gluten-sensitive celiac enteropathy, associated with characteristic villous atrophy. Measured by a noninvasive method, the ratio of caffeine metabolites excreted in the urine after a caffeine challenge had previously been shown to be indicative of the total xanthine oxidase activity of the patient.

METHODS

The study involved 22 children with gluten-challenged celiac disease, exhibiting subtotal villous atrophy in specimens from the third intestinal biopsy in accordance with ESPGHAN criteria. Ten of the patients displayed overt clinical symptoms (active form), whereas 12 had no symptoms (silent form). Urinary caffeine metabolites were determined by high-pressure liquid chromatography. The total in vivo xanthine oxidase activity was expressed as the caffeine metabolite index.

RESULTS

In patients with active celiac disease the xanthine oxidase activity index was considerably higher, whereas in those with silent disease it was significantly lower than the control value. A significant negative correlation was shown between the index indicative of xanthine oxidase activity and the serum iron level of the patients.

CONCLUSIONS

Activation of xanthine oxidase may play a role in the pathogenesis of active celiac disease with definite malabsorption, gastrointestinal symptoms, and anemia. The caffeine test reflects the difference in the pathogenetic mechanism leading to the mucosal lesion and clinical symptoms of active and silent forms of celiac disease.

Gluten-free diet decreases urinary peptide levels in children with celiac disease

BACKGROUND

Increased urine secretion of peptides has been found in celiac disease, probably resulting from increased intestinal uptake of peptides caused by damage to the small gut mucosa.

METHODS

High-performance liquid chromatography of low-molecular-weight peptides in the urine was performed over 6 months, before and after a gluten-free diet was instituted in children who clinically improved while consuming the diet.

RESULTS

A significant decrease of peptide levels was observed in children consuming the gluten-free diet. Certain peptide peaks thought to be gluten related decreased the most after the patients began the diet.

CONCLUSIONS

Because the peptides decrease in patients consuming a gluten-free diet, it is reasonable to conclude that such peptides have a mostly dietary origin.

Measurement of small intestinal permeability markers, lactulose, and mannitol in serum: results in celiac disease

To date, tests of small intestinal passive permeability have involved the ingestion of test molecules whose permeation is assessed indirectly by measuring their urinary recovery. Excretion ratios of marker molecules (eg, lactulose-to-mannitol excretion ratio, LMER) are useful clinically. Measurement of permeability markers in serum would improve the convenience of the tests. Our aim was to assess small intestinal permeability in celiac patients using serum lactulose and mannitol levels with calculation of lactulose to mannitol serum ratios (LMSR) and to compare the results with the standard methods using urinary recoveries. Twenty-four newly diagnosed celiacs and 10 control subjects were studied; 10 celiacs were restudied while established on a gluten-free diet. Test subjects and patients ingested 10 g lactulose and 2.5 g mannitol in 50 ml water. In 10 untreated celiacs and the controls, blood was taken from 0 to 120 min and all urine was collected for 6 hr. The remaining 14 untreated and the 10 treated celiacs had a single serum sample taken 60 min after ingestion of the test solution. At 1 hr after ingestion, the mean mannitol level in normals (0.156 mmol/liter) was significantly higher than in untreated celiacs (0.06 mmol/liter). The 1-hr mean serum lactulose level in normals (0.125 micromol/liter) was significantly lower than in untreated celiacs (0.56 micromol/liter). The median 1-hr LMSR in untreated celiacs was 0.42 compared with 0.039 in normals and 0.08 in treated celiacs. There was a significant correlation between LMSR and LMER. Permeability testing using serum measurements of lactulose and mannitol gave comparable results in celiac patients to the tests using urinary recovery of the permeability markers and may prove to be more convenient, especially in pediatric patients.

Significantly increased levels of nitric oxide products in urine of children with celiac disease

BACKGROUND

Celiac disease is characterized by morphologic and functional aberrations of the small intestinal mucosa, i.e., crypt hyperplasia, villous atrophy, infiltration of intraepithelial lymphocytes, and alteration of permeability. Nitric oxide has been shown to affect mucosal permeability after ischemia-reperfusion, but little is known about the regulatory role of nitric oxide in celiac disease. The purpose of this study was to assess nitric oxide production in children with celiac disease and in control subjects.

METHODS

The sum of nitrite and nitrate in the urine was measured with a colorimetric method in 137 children with a median age of 3 years, 84 patients and 53 reference children, all of whom underwent a small intestinal biopsy to confirm or overrule suspicion of celiac disease.

RESULTS

Median urinary nitrite-nitrate concentration in celiac children was 3323 microM (4147 +/- 1102; mean +/- SEM) at first clinical examination and 2501 microM (2939 +/- 386) after gluten challenge, which was significantly higher than concentrations in reference children (1029 microM; 1174 +/- 116) and in children with celiac disease on a gluten-free diet (882 microM; 1369 +/- 360) (p < 0.0001).

CONCLUSIONS

A gluten-containing diet is associated with an increased nitrite-nitrate secretion in the urine in children with celiac disease, presumably as a result of nitric oxide synthase activation and nitric oxide production in the diseased small intestinal mucosa.

Simultaneous HPLC determination with light-scattering detection of lactulose and mannitol in studies of intestinal permeability in pediatrics

We describe a new HPLC method for the simultaneous determination of lactulose and mannitol in urine, in which cation-exchange chromatography and evaporative light-scattering detection are used. The two sugars are orally administered for the estimation of intestinal permeability in children. Samples were purified by solid phase extraction on a C18 cartridge and subsequent addition of anion-exchange resin. Cellobiose may be used as an internal standard. The chromatographic separation was carried out in 16 min at a flow rate of 0.5 mL/min, using deionized water as the mobile phase. Within-run precision (CV) measured at three concentrations was 1.6-2.3% for lactulose and 1.0-1.9% for mannitol. Between-run CVs were 2.1-4.1% and 1.3-2.7% for lactulose and mannitol, respectively. Analytical recovery of both sugar probes was 97-101%. The detection limits (signal-to-noise ratio = 3) were 0.82 mg/L for lactulose and 0.65 mg/L for mannitol. The lactulose/ mannitol ratio in control subjects was 0.024 +/- 0.006; in patients with Crohn's and coeliac diseases in active phase, the ratios were 0.200 +/- 0.082 and 0.072 +/- 0.025, respectively. The method is rapid, simple, and sensitive, and suitable for determination of intestinal permeability in children.

Peptide excretion in celiac disease

BACKGROUND

In celiac disease, the mucosa in the small intestine is damaged. This study was conducted to determine whether the normal peptide and protein uptake from the gut is increased in patients with celiac disease.

METHODS

The low-molecular-weight peptides were measured in urine from children and adults with untreated celiac disease. A reversed-phase technique was used.

RESULTS

The excretion of peptides increased compared with that in an age- and sex-matched reference group.

CONCLUSIONS

Celiac patients have hyperpeptiduria. It is possible that some of these peptides are bioactive and may mediate varying systemic effects also found in untreated celiac disease.

Is the sugar intestinal permeability test a reliable investigation for coeliac disease screening?

BACKGROUND

The lactulose/mannitol (L/M) intestinal permeability test is a simple, non-invasive screening test for coeliac disease. The reliability of the L/M test has so far only been tested in selected groups of patients with coeliac disease.

AIM

To evaluate the reliability of the L/M test in a group of patients with coeliac disease who had been diagnosed during mass serological screening of the general population.

PATIENTS AND METHODS

Twenty nine patients with coeliac disease detected by screening and 54 age matched coeliac disease free controls aged 11-15 years underwent an L/M test with 5 g lactulose and 2 g mannitol in isotonic aqueous solution. Urinary sugars were measured by high performance liquid chromatography.

RESULTS

The median % urinary recovery of lactulose (lactulose UR) was significantly higher in patients with coeliac disease than in controls (0.63 v 0.18, p < 0.001). The mean mannitol % UR was lower in patients with coeliac disease than in controls (17.6 v 18.5) but the difference was not significant. The median urinary L%/M% ratio was significantly higher in patients with coeliac disease than in controls (0.038 v 0.014, p < 0.001). However, 16 of the 29 patients with coeliac disease showed an L%/M% ratio within normal limits (< 0.044).

CONCLUSIONS

The L/M intestinal permeability test is not a valuable tool for screening of coeliac disease in the general population. The pattern of the urinary probe recovery suggests that many patients with coeliac disease could remain symptomless because the extent of their intestinal mucosal damage is small ("short" coeliac disease).

Follow-up of celiac disease with D-xylose breath test

Hydrogen breath tests (H2-BT) are commonly used to diagnose carbohydrate malabsorption. Specifically, the H2-BT with D-xylose has been shown to be as valid as the traditional urinary test for the recognition of intestinal malabsorption. We have now investigated the H2-BT with D-xylose in the follow-up of patients with celiac disease. Seventeen patients with celiac disease established clinically and confirmed by jejunal biopsy were studied. H2-BT was performed before and after treatment with a gluten-free diet for at least five months. Alveolar breath samples were obtained before administering orally 25 g of D-xylose and thereafter at 30 min intervals for 5 hr. Samples were analyzed for H2 by chromatography. Simultaneously, the 5-hr urinary excretion of D-xylose was determined by colorimetry. Gluten removal significantly decreased the H2 delta change (from 56.5 +/- 5.9 ppm to 32.2 +/- 8.8, P < 0.05). A similar decrease was observed in the area under the curve (P < 0.05). Conversely, urinary D-xylose excretion increased significantly (P < 0.05). Eleven of the 17 celiacs clinically improved after treatment. The H2-BT normalized in every patient who entered remission on the gluten-free diet, whereas the urinary D-xylose excretion remained abnormal in six of them. In the six nonresponder patients the H2-BT remained high in five, whereas urinary D-xylose excretion paradoxically normalized in 2. We conclude that H2-BT with D-xylose is a useful and practical test for the follow-up of celiac disease and is simpler and more reliable than the urinary D-xylose test.

Evaluation of differential disaccharide excretion in urine for non-invasive investigation of altered intestinal disaccharidase activity caused by alpha-glucosidase inhibition, primary hypolactasia, and coeliac disease

BACKGROUND/AIM

The reliability of a quantitative method for the non-invasive assessment of intestinal disaccharide hydrolysis was assessed.

METHODS

Differential excretion of intact disaccharide, expressed as ratios of lactulose to appropriate hydrolysable disaccharides in urine collected following combined ingestion, has been investigated in healthy volunteers with drug induced alpha-glucosidase inhibition, in subjects with primary hypolactasia, and patients with coeliac disease.

RESULTS

Oral administration of the alpha-glucosidase inhibitor 'Acarbose' (BAY g 5421, 200 mg) together with sucrose and lactulose increased the urinary sucrose/lactulose excretion ratios (% dose/10 h) fivefold. The effect was quantitatively reproducible, a higher dose of 'Acarbose' (500 mg) increasing the excretion ratio to about 1.0 indicating complete inhibition of intestinal sucrase activity. The suitability of the method for measuring differences in dose/response and duration of action was assessed by comparing three different alpha-glucosidase inhibitors (BAY g 5421, BAY m 1099, and BAY o 1248) and found to be satisfactory. Subjects with primary adult hypolactasia had urine lactose/lactulose excretion ratios raised to values indicating reduced rather than complete absence of lactase activity whereas sucrose/lactulose ratios were not significantly affected. 'Whole' intestinal disaccharidase activity assessed by this method demonstrated impairment of lactase, sucrase, and isomaltase in eight, one, and seven, respectively, of 20 patients with coeliac disease. By contrast in vitro assay of jejunal biopsy tissue indicated pan-disaccharidase deficiency in all but five of these patients. This shows the importance of distinguishing between 'local' and 'whole' intestinal performance.

CONCLUSIONS

Differential urinary excretion of ingested disaccharides provides a reliable, quantitative, and non-invasive technique for assessing profiles of intestinal disaccharidase activity.

The value of the D-xylose test compared with the differential sugar absorption test in recognizing coeliac disease

OBJECTIVE

To compare the value of the differential sugar absorption test (SAT) with the blood and urine D-xylose tests (DXTs and DXTu) in diagnosing coeliac disease (CD) the SAT and the standard DXTs and DXTu were performed in 14 coeliacs with abnormal small bowel histology and in 12 patients with aspecific gastrointestinal complaints.

METHODS

In the SAT a solution of lactulose (L) and mannitol (M) was given to the fasting patient after which the L/M ratio was measured in 5 h urine by gas chromatography. In the DXTs and DXTu a solution of 25 g D-xylose was given to the fasting patient and blood was drawn at 0, 30 and 120 min and urine was collected for 5 h, respectively.

RESULTS

To measure the power in diagnosing CD of the SAT, DXTs 30 min, DXTs 120 min and DXTu, the test results were plotted in ROC curves and the areas under the curves (AUCs) were calculated. The AUCs were 0.97, 0.77, 0.78 and 0.63, respectively.

CONCLUSION

In our opinion, the DXTs and DXTu are no longer useful in the investigation of mucosal function of the small bowel.

Hypocalciuria in overt and subclinical celiac disease

OBJECTIVE

To investigate indices of calcium (Ca) homeostasis in celiac disease (CD).

METHODS

Urinary Ca excretion rate, intestinal absorption of strontium (Sr) (used as index of intestinal Ca absorption), and other variables related to these end points were measured in newly diagnosed, untreated adult patients (n = 32) with overt and subclinical CD and compared with those of healthy controls (n = 27). Subclinical CD was defined by the absence of diarrhea (> or = 3 bowel movements/24 h), steatorrhea (fecal fat excretion > 6 g/24 h), and low body mass index (weight/height, kg/m2 < 21).

RESULTS

Compared with controls, untreated celiac patients had 2 x lower Ca excretion (p < 0.0001) in 24-h and overnight urine (fed condition) but normal Ca excretion in urine samples collected under fasting (2-h) condition; the increase in urinary Ca excretion from fast to fed condition was 4 x lower in untreated celiac patients (p < 0.0001). Patients with overt and subclinical CD did not have significantly different urinary Ca excretion rates. Sr absorption rate was 45% lower in untreated patients than controls (p < 0.0001). Patients with overt and subclinical CD did not have significantly different Sr absorption rates. Sr absorption rate (r = 0.576, p < 0.0001) related to the increase in urinary Ca excretion from fast to fed condition. In celiac patients, 24-h urinary Ca excretion increased by 52% (p < 0.0001) over baseline after 6 months of gluten-free diet, and urinary Ca excretion under fasting condition did not significantly change.

CONCLUSIONS

Overt and subclinical CD is associated with low urinary Ca excretion under fed condition, which relates to low intestinal absorption.

HPLC determination of polyethylene glycol 400 in urine: oligomeric profile in healthy and celiac disease subjects

The absorption of orally administered polyethylene glycol (PEG) has been used to assess intestinal permeability. We describe a simple HPLC technique to determine the oligomeric profile of PEG excreted in urine. We measured the total (%) PEG excreted in 6 h and the ratio of the four smallest oligomers to the three largest oligomers (expressed as mean percentages). The proposed method differentiates distinct groups of subjects with varying degrees of intestinal permeability detected by intestinal biopsy. The percent of PEG excreted and the oligomer ratio values for healthy subjects were, respectively, 30.1 +/- 3.87 and 0.35 +/- 0.03; for celiac patients on a gluten-free diet, 24.5 +/- 6.65 and 0.45 +/- 0.16; and for celiac patients, 15.0 +/- 5.93 and 1.12 +/- 0.55.

Intestinal permeability after single dose gluten challenge in coeliac disease

The changes of intestinal permeability before and after a gluten load were studied. The study group comprised 27 patients with coeliac disease (mean age 12.3 years) and 19 healthy controls matched by sex and age. Intestinal permeability was studied by measuring the urinary excretion of two sugars, lactulose and L-rhamnose, before and six hours after the ingestion of five palatable biscuits made with 50 g of gluten powder. The patients with coeliac disease had been on a gluten free diet during the previous two years. After the gluten load lactulose and L-rhamnose urinary excretion changed significantly in patients, and a significant increase in the lactulose: L-rhamnose ratio was also observed. No significant changes were observed in the controls. In view of the modification of the three biopsies diagnostic protocol made by the European Society for Paediatric Gastroenterology and Nutrition, permeability tests associated with single gluten challenges may be an added contribution to the accuracy of the diagnosis in childhood.

Urinary oxalate recovery after oral oxalic load: an alternative method to the quantitative determination of stool fat for the diagnosis of lipid malabsorption

Urinary oxalate concentrations were measured in 45 patients with quiescent Crohn's disease, four patients with chronic pancreatitis and five healthy subjects after a normal oxalate (150 g/day) diet, after a high-fat (150 g/day), normal oxalate diet and after and after a high-oxalate (500 mg/day) diet. Urinary oxalate concentrations were significantly (P less than 0.05) higher in patients with Crohn's disease and steatorrhoea, but not in those with chronic pancreatitis, after administrating a high-oxalate diet compared with healthy subjects. Mean oxalate values were 19.1 mg/24 h in controls compared with 65.8 mg/24 h in Crohn's disease patients. A direct correlation (r = 0.37, P less than 0.01) was established between faecal rats and urinary oxalate after oval oxalate load: this correlation (r = 0.43, P less than 0.01) is closer when only patients with Crohn's disease are considered. The study, therefore, confirmed a correlation between steatorrhoea and hyperoxaluria in patients with Crohn's disease; however, the high percentage of false positive results limits the use of urinary oxalate concentrations as a reliable indicator of lipid malabsorption. It is concluded that, at present, measurement of urinary oxalate cannot be recommended as a valid alternative to the Van de Kamer method for diagnosing lipid malabsorption.

Lactulose/mannitol test: an ideal screen for celiac disease

A lactulose/mannitol (La/Ma) test was compared with a standard cellobiose/mannitol test (Ce/Ma) in 17 patients with newly diagnosed celiac disease and 12 healthy controls. The mean La/Ma test was 0.163 (SEM 0.076) in celiacs and 0.016 (SEM 0.002) in controls. The mean Ce/Ma test was 0.132 (SEM 0.024) in celiacs and 0.014 (SEM 0.002) in controls (p less than 0.001). There is no significant difference between the new La/Ma test and the Ce/Ma test. Eighty-two patients referred to a general gastroenterology clinic with symptoms or signs of celiac disease performed a La/Ma test. A jejunal biopsy was indicated in 44 of these. In this selected group the sensitivity was 89%, specificity 54%, and negative predictive value of 95%. The La/Ma test fulfills the criteria of a screening test; it is sensitive, of low cost, and simple to perform, and it has the advantage of a simple enzyme assay and does not cause diarrhea in patients with hypolactasia. It can, therefore, be used in screening large patient populations.

Comparison between the cellobiose/mannitol and 51Cr-labelled ethylenediaminetetra-acetate absorption tests in the detection of coeliac disease

1. The cellobiose/mannitol and 51Cr-labelled ethylenediaminetetra-acetate (51Cr-EDTA) absorption tests have been compared with respect to their ability to detect altered intestinal permeability in coeliac disease. 2. In patients with clinically proven coeliac disease, 13 out of 14 (93%) had abnormal urinary cellobiose/mannitol ratios, while only five out of 12 (42%) had abnormal urinary recoveries of 51Cr-EDTA. Thus, the cellobiose/mannitol absorption test is more sensitive in recognizing coeliac disease and this difference was significant (P less than 0.02). 3. Possible reasons for this difference in the sensitivity of the two absorption tests are discussed.

Detection of pancreatic steatorrhea by oral pancreatic function tests

Pancreolauryl and NBT-PABA tests were performed in urine of 54 patients with exocrine pancreatic insufficiency and, additionally, in serum of 29 of these patients. All patients underwent a secretin-pancreozymin test and a 72-hr fecal fat analysis. Pancreatic steatorrhea occurred (with only three exceptions) when the pancreolauryl test revealed a T/C ratio [recovery of the fluorescein of the test (T) and the control (C) day] of less than 10, or when serum fluorescein concentrations were below 0.5 microgram/ml. The NBT-PABA test also showed a negative correlation between urinary PABA excretion or serum PABA concentration and fecal fat excretion, but there was no diagnostically useful cutoff limit indicating decompensation of exocrine pancreatic insufficiency. These findings indicate that the pancreolauryl test may facilitate clinical evaluation of patients with chronic pancreatitis by simultaneously assessing exocrine pancreatic insufficiency as a cause and predicting pancreatic steatorrhea as a sequel of maldigestion. In clinical practice, the pancreolauryl test can be used as a parameter for deciding whether to initiate pancreatic enzyme substitution if direct pancreatic function tests and fecal fat analysis are not available.

Urinary mannitol: lactulose excretion ratios and jejunal mucosal structure

A dual sugar (mannitol, lactulose) absorption test was evaluated using an iso-osmolar oral dose in two groups of children: a study group of 43 children divided into five subgroups, based on severity of mucosal damage, and a control group of 53 children with histologically normal jejunal biopsy specimens. After an oral dose, the three hour urinary mannitol: lactulose ratios in the control group showed a highly significant positive correlation with body surface area. After correction for the body surface area relationship, a control lower limit was defined by the mean -2SD of the log10 transformed control mannitol: lactulose ratios. Specificity and sensitivity for severe villous atrophy was 98% and 95% respectively but the sensitivity declined rapidly with decreasing degrees of mucosal damage, and the test would not therefore be an adequate screening procedure for all enteropathies. In sequential studies in 18 children, the changes in the mannitol: lactulose ratio were consistent with the changes in mucosal structure induced by gluten challenge or gluten withdrawal. The test may therefore have a role in any sequential study of lesions of the mucosa of the small intestine.

[Measurement of intestinal permeability to sugars: application in the diagnosis of celiac disease and cow's milk protein enteropathy]

Intestinal permeability to macromolecules was studied by measuring differential urinary elimination of two orally ingested non-metabolizable sugars of different molecular size, mannitol and lactulose. In 25 control children, mannitol and lactulose urinary elimination were 16.30 +/- 5.77% and 0.33 +/- 0.10% of ingested dose, respectively, with a mean lactulose/mannitol (M/M) urinary ratio of 2.73 +/- 0.70%. In 7 celiac children, L/M ratio exhibited a significant rise: 8.53 +/- 2.54% (p less than 0.001). In 7 children with cow's milk sensitive enteropathy under exclusion diet, L/M ratio was normal in fasting condition: 2.63 +/- 1.28% and raised significantly during provocation test with milk: 7.22 +/- 3.88% (p less than 0.01). Intestinal permeability test is a reliable index of villous atrophy and cow's milk sensitive enteropathy.

Intestinal permeability to [51Cr]EDTA in children with Crohn's disease and celiac disease

[51Cr]EDTA was used as a probe molecule to assess intestinal permeability in 7 healthy control adults, 11 control children, 17 children with Crohn's disease, and 6 children with untreated celiac disease. After subjects fasted overnight, 75 kBq/kg (= 2 microCi/kg) 51Cr-labeled EDTA was given by mouth; 24-h urinary excretion of [51 Cr]EDTA was measured and expressed as a percentage of the total oral dose. Mean and SD were as follows: control adults 1.47 +/- 0.62, control children 1.59 +/- 0.55, and patients with Crohn's disease or celiac disease 5.35 +/- 1.94. The difference between control children and patients was statistically significant (p less than 0.001). These results show that intestinal permeability to [51Cr]EDTA is increased among children with active or inactive Crohn's disease affecting small bowel only or small bowel and colon, and with untreated celiac disease. The [51Cr]EDTA permeability test could facilitate the decision to perform more extensive investigations in children suspected of small bowel disease who have atypical or poor clinical and biological symptomatology.

Evaluation of a gliadin-containing gluten-free product in coeliac patients

Gluten-free products based on wheat starch contain gliadin which exacerbates coeliac disease. A cross-over study was carried out in which ten treated coeliac patients ingested six slices daily of home-baked gliadin-containing gluten-free bread for 6 weeks. While jejunal biopsy morphometry and 51Cr-EDTA excretion were similar after the test and control periods, four of the subjects reported diarrhoea associated with the gliadin-contaminated gluten-free product. Wheat starch-based gluten-free products can cause persistent symptoms in treated coeliac patients.

Oxalate-loading tests to screen for steatorrhoea: an appraisal

We have evaluated two procedures as screening tests for steatorrhoea: firstly, a simplified, two-day, oxalate-loading test and secondly the rate of urinary oxalate excretion following a single oral dose of oxalate. Following two-day oxalate loading there was almost complete overlap of the values for 24-h urinary oxalate between 15 apparently healthy volunteers and 10 patients with steatorrhoea. The rate of oxalate excretion following a single dose of oxalate was increased in one patient with Crohn's disease and ileal resection who had normal faecal fat excretion, but three patients with steatorrhoea due to other causes had normal rates of excretion. We conclude that these oxalate-loading tests are not a useful alternative to faecal fat estimation in patients with suspected malabsorption.