CPT1A and hyperinsulinemic hypoglycemia, familial, 4: Thus, we evaluated whether MS/MS measurement of deuterium-labeled acylcarnitines in peripheral blood mononuclear cells (PBMCs) after the load of deuterium-labeled palmitic acid (d31-PA) and deuterium-labeled octanoic acid (d15-OA) was effective to diagnose CPT-I deficiency.