Delaware Valley Mass Spectrometry Discussion Group

Abstract: Larger clinical laboratories perform hundreds of unique tests daily to provide clinical care. Testing can be categorized as routine screening, direct diagnostic, confirmatory, or disease/drug monitoring. Each test within these categories comes with associated criteria, such as accuracy, sensitivity, and stability. To meet these high standards, mass spectrometry (MS) based testing is a key solution.

The field of inborn errors in metabolism (IEM) is an example where oftentimes highly complex panels are performed such as organic acids and amino acids. This presentation will focus on the development of a novel MS-based ketone body panel to provide clinical information of inherited mitochondrial diseases, such as Leigh Syndrome. These diseases cause defects in the energy metabolism, resulting in abnormalities in the mitochondrial redox state. Using the ratio between the ketone bodies: beta-hydroxybutyrate (BHB) and acetoacetate (AcAc) an estimation of the hepatic intramitochondrial NADH/NAD+ ratio can be made which reflects the mitochondrial redox state. In addition to BHB and AcAc, three isomers were added to the panel (i.e., alpha-hydroxybutyrate (AHB), gamma-hydroxybutyrate (GHB), and beta-hydroxyisobutyrate (BHIB)) to provide additional metabolic pathway coverage and clinical insight. The measurement of BHB/AcAc is extremely challenging due to the stability of AcAc; thus far no clinically validated assay was available. The clinical implications, stability study, and validation of these components will be discussed during this session, in addition to the in-house synthesized AcAc internal standard that was used.