Measurement of Small Intestinal Permeability Markers, Lactulose, and Mannitol in Serum (Results in Celiac Disease)

To date, tests of small intestinal passivepermeability have involved the ingestion of testmolecules whose permeation is assessed indirectly bymeasuring their urinary recovery. Excretion ratios ofmarker molecules (e.g., lactulose-to-mannitolexcretion ratio, LMER) are useful clinically.Measurement of permeability markers in serum wouldimprove the convenience of the tests. Our aim was toassess small intestinal permeability in celiac patients using serumlactulose and mannitol levels with calculation oflactulose to mannitol serum ratios (LMSR) and to comparethe results with the standard methods using urinary recoveries. Twenty-four newly diagnosed celiacsand 10 control subjects were studied; 10 celiacs wererestudied while established on a gluten-free diet. Testsubjects and patients ingested 10 g lactulose and 2.5 g mannitol in 50 ml water. In 10untreated celiacs and the controls, blood was taken from0 to 120 min and all urine was collected for 6 hr. Theremaining 14 untreated and the 10 treated celiacs had a single serum sample taken 60 min afteringestion 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 serumlactulose level in normals (0.125 μmol/liter) wassignificantly lower than in untreated celiacs (0.56μmol/liter). The median 1-hr LMSR in untreatedceliacs was 0.42 compared with 0.039 in normals and 0.08 intreated celiacs. There was a significant correlationbetween LMSR and LMER. Permeability testing using serummeasurements of lactulose and mannitol gave comparable results in celiac patients to the tests usingurinary recovery of the permeability markers and mayprove to be more convenient, especially in pediatricpatients.