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The free fatty acid and total fatty acid profiles in plasma of nine patients with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, two with very-long-chain acyl-CoA dehydrogenase (VLCAD) deficiency and two with mild-type multiple acyl-CoA dehydrogenase (MAD-m) deficiency, were analyzed by gas chromatography-mass spectrometry. In the plasma of patients with MCAD deficiency we found increases of octanoic acid (8:0), decanoic acid (10:0), 4-decenoic acid (10:1 omega 6), and 4,7-decadienoic acid (10:2 omega 3), all present almost exclusively in free form. The patients with VLCAD deficiency showed increases of mainly 5-tetradecenoic acid (14:1 omega 9) and to a minor extent 5-dodecenoic acid (12:1 omega 7), 5,8-tetradecadienoic acid (14:2 omega 6), and 7,10-hexadecadienoic acid (16:2 omega 6), in both the free and esterified fatty acid fraction. The MAD-m patients showed variable increases of all the unusual fatty acids present in MCAD- and VLCAD-deficient plasma. The 14:1 omega 9, 14:2 omega 6, and 16:2 omega 6 fatty acids were present mainly in the esterified form. Measurement of these fatty acids in plasma by the relatively simple method presented here provides a sensitive and specific aid in the diagnosis of acyl-CoA dehydrogenase deficiency disorders.

Current techniques for the determination of very-long-chain fatty acids from biological samples require laborious procedures including solvent extraction of lipids, purification, hydrolysis, derivatization, purification of derivatized fatty acids by thin-layer chromatography and finally gas chromatographic analysis. A comparison was made between such a procedure based on solvent extraction and a method based on a recently developed direct one-step transesterification reaction. The latter method proved to be much faster and led to higher recoveries of all individual very-long-chain fatty acids from both plasma and skin fibroblasts. The assay proved to be very convenient in the diagnosis of genetically determined disorders in which very-long-chain fatty acids accumulate in tissues and body fluids. Because of its simplicity and speed and because it can be performed with as little as 100 microliters of plasma, the method can be recommended as a valuable screening procedure for peroxisomal disorders.