Urinary lactulose/mannitol ratio

Method

Ratio of lactulose to mannitol recovered in urine following an oral dual-sugar challenge, quantified by HPLC or LC-MS. Collection window recorded on the edge -- 5-hour and 24-hour collections index different intestinal regions.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

Will be confused with the dual-sugar ratio using L-rhamnose as the reference: same paracellular probe, different transcellular reference, effect sizes an order of magnitude apart within the same meta-analysis (PMID 38361147). Also distinct from plasma zonulin and plasma LPS-binding protein, marketed as interchangeable permeability markers but blood analytes measured without any probe challenge, and correlating poorly with sugar recovery.