A kinetic assay of total lipase activity for detecting lysosomal acid lipase deficiency (LAL-D) and the molecular characterization of 18 LAL-D patients from Russia.

Unlabelled: Laboratory diagnostics of lysosomal acid lipase deficiency (LAL-D), a rare disorder associated with alterations, are based on the evaluation of LAL activity. In dry blood spots (DBS) submitted for LAL-D diagnostics (the screening cohort) over a two-year period or obtained from a cohort of retrospective LAL-D patients, we measured: (1) LAL activity using a two-reaction assay with 4-methylumbelliferone palmitate (4-MU-Palm) and Lalistat-2, a specific LAL inactivator; (2) total lipase (TL) activity by a 1-hour kinetic 4-MU-Palm cleavage reaction (no Lalistat-2). The TL activity was expressed as the area under the kinetic curve after 1 hour (TL-AUC) of the reaction and presented as the median (min-max).