Peroxisomes are organelles surrounded by membrane in the form of spheres. Peroxisomes play an important role in beta oxidation of very long chain fatty acids (C22:0, C24:0, C26:0) and alpha oxidation of 3-methyl fatty acids (phytanic acid). The Zellweger syndrome is best known peroxisomal disorders. Zellweger syndrome is a rare disease characterized by decreased or absent peroxisomes in the cells of the liver, kidney and brain. Increased levels of very long chain fatty acids (VLCFA) in blood and decreased plasmalogen levels in erythrocytes are the most important parameters to aid in diagnosis.

Very long-chain fatty acids, (VLCFA) pristanic and phytanic acid analysis to aid in diagnosis of peroxisomal biogenesis disorders (Zellweger Syndrome Spectrum), X-linked adrenoleukodystrophy (X- ALD). The diagnosis of X-ALD may be raised by the above clinical signs or symptoms, including isolated adrenal insufficiency and is commonly achieved by laboratory evaluation of increased concentrations of VLCFA in plasma. Testing typically includes eight VLCFA parameters: the level of C22:0, C24:0, C26:0, pristanic and phytanic acid and the ratio of C26:0/ C22:0, C24:0/C22:0, pristanic acid/phytanic acid.