Researchers presented a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) acylcarnitine analysis method that allows users to comprehensively view plasma acylcarnitines. The new tool could potentially be used as an alternative first-tier clinical method to diagnose inherited disorders of fatty acid oxidation such as long-chain fatty acid oxidation disorders (LCFAOD). 

The researchers led by Marcus Miller, PhD, of the Department of Medical and Molecular Genetics, Indiana University School of Medicine in Indianapolis, tested the utility of the new assay by analyzing 250 residual patient specimens.

“Application of this method to the analysis of clinical samples suggests that the advantages of LC-MS/MS acylcarnitine analysis as a first-tier test outweigh the inherent disadvantages/challenges,” they wrote, in the abstract for a poster scheduled to be presented at the 43rd Annual Meeting of the Society for Inherited Metabolic Disorders.

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Using a novel mixed-mode chromatographic approach, the team separated acylcarnitines, free carnitine, and carnitine metabolic precursors and quantified them by tandem mass spectrometry.

“Our LC-MS/MS acylcarnitine analysis was subjected to a full clinical validation that generally found excellent performance metrics including improved specificity, linearity, and limits of quantification compared to our lab’s FI-MS/MS acylcarnitine method,” the researchers wrote. 

The analysis of the 250 patient specimens showed that the new method correctly identified all the disease-associated biomarkers that can be detected by flow-injection tandem mass spectrometry (FI-MS/MS), the prevailing clinical method used to study acylcarnitines. Moreover, the new method provided a much more granular view of acylcarnitine abnormalities, according to the authors. For example, it could detect many clinically relevant isomeric/isobaric acylcarnitine species that remain ambiguous with FI-MS/MS.

“The improved limits of quantification provided by LC-MS/MS enabled us to monitor long chain and very long chain dicarboxylic acylcarnitines,” the authors said.

Some of the disadvantages of the new method compared to FI-MS/MS are longer and more complicated data analyses and a lack of commercial acylcarnitine reference material.


Luna C, Chandler G, Lah M, et al. Is it time to move beyond acylcarnitine profiles? Lessons from the clinical application of a high definition LC-MS/MS acylcarnitine method. Poster presented at: Society for Inherited Metabolic Disorders 43rd Annual Meeting; April 10-13, 2022; Orlando, Florida. Poster 56.