[Diagnosis of small intestinal bacterial overgrowth in children: the use of lactulose in the breath hydrogen test as a screening test]. / Diagnóstico de proliferación bacteriana intestinal en niños: evidencia experimental para sustentar el empleo de lactulosa en la prueba de hidrógeno y su validación como prueba tamiz.

INTRODUCTION: The standard method for diagnosis of small intestinal bacterial overgrowth is a duodenal aspirate that produces a coliform count greater than 10(5) colonic forming units/ml. Because this is an invasive procedure, the lactulose breath hydrogen test is considered as a non-invasive alternative. Better experimental support is required, however, for the routine use of lactulose in diagnosis. OBJECTIVE: Experimental evidence is provided to support the use of lactulose in the breath hydrogen test. Validation of the test is accomplished by comparison to the duodenal aspirate culture. MATERIALS AND METHODS: A rational basis for the use of lactulose was established by a comparison of the kinetics of lactulose and lactose on intestinal lactase. For validation, the hydrogen test was applied to 47 children suffering from gastrointestinal disorders, and the results compared with aspirate culture counts. The validity of the hydrogen test was assessed by a contingency table and the degree of agreement established by the kappa index. RESULTS: The kinetics data showed that lactase is 240 times less efficient in presence of lactulose than it is in presence of lactose. The sensitivity of the breath hydrogen test was 85.7% (82.0-89.4%), its specificity 90.9% (89.3-92.5%), the predictive positive value 80.0% (76.5-83.5%) and the predictive negative value 93.8% (92.1-95.4%); the kappa index=0.785 (0.54-0.95) showed excellent agreement between the two diagnostic tests. CONCLUSION: The results provided experimental support for the use of lactulose in the breath hydrogen test, and it was validated as screening test in the diagnosis of small intestinal bacterial overgrowth.