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 i ngestion of test molecules whose permeation is assessed indirectly by measu ring their urinary recovery. Excretion ratios of marker molecules (eg, lact ulose-to-mannitol excretion ratio, LMER) are useful clinically. Measurement of permeability markers in serum would improve the convenience of the test s. Our aim was to assess small intestinal permeability in celiac patients u sing serum lactulose and mannitol levels with calculation of lactulose to m annitol serum ratios (LMSR) and to compare the results with the standard me thods 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 a nd 2.5 g mannitol in 50 mi water. In 10 untreated celiacs and the controls, blood was taken from 0 to 120 min and all urine was collected for 6 hr. Th e remaining 14 untreated and the 10 treated celiacs had a single serum samp le taken 60 min after ingestion of the test solution. At 1 hr after ingesti on, the mean mannitol level in normals (0.156 mmol/liter) was significantly higher than in untreated celiacs (0.06 mmol/liter). The l-hr mean serum la ctulose level in normals (0.125 mu mol/liter) was significantly lower than in untreated celiacs (0.56 mu mol/liter). The median l-hr LMSR in untreated celiacs was 0.42 compared with 0.039 in normals and 0.08 in treated celiac s. 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 perme ability markers and may prove to be more convenient, especially in pediatri c patients.