Lactulose: mannitol diagnostic test by HPLC and LC-MSMS platforms: considerations for field studies of intestinal barrier function and environmental enteropathy.

OBJECTIVES: The lactulose:mannitol (L:M) diagnostic test is frequently used in field studies of environmental enteropathy (EE); however, heterogeneity in test administration and disaccharide measurement has limited the comparison of results between studies and populations. We aim to assess the agreement between L:M measurement between high-performance liquid chromatography with pulsed amperometric detection (HPLC-PAD) and liquid chromatography-tandem mass spectrometry (LC-MSMS) platforms. METHODS: The L:M test was administered in a cohort of Peruvian infants considered at risk for EE. A total of 100 samples were tested for lactulose and mannitol at 3 independent laboratories: 1 running an HPLC-PAD platform and 2 running LC-MSMS platforms. Agreement between the platforms was estimated. RESULTS: The Spearman correlation between the 2 LC-MSMS platforms was high (ρ ≥ 0.89) for mannitol, lactulose, and the L:M ratio. The correlation between the HPLC-PAD platform and LC-MSMS platform was ρ = 0.95 for mannitol, ρ = 0.70 for lactulose, and ρ = 0.43 for the L:M ratio. In addition, the HPLC-PAD platform overestimated the lowest disaccharide concentrations to the greatest degree. CONCLUSIONS: Given the large analyte concentration range, the improved accuracy of LC-MSMS has important consequences for the assessment of lactulose and mannitol following oral administration in populations at risk for EE. We recommend that researchers wishing to implement a dual-sugar test as part of a study of EE use an LC-MSMS platform to optimize the accuracy of results and increase comparability between studies.