Specific tests - Amino acid chromatography (urine, serum) - Oligosaccharide chromatography (urine, serum) - Mucopolysaccharide electrophoresis (urine) - Amino acids (quantitative) - Organic acids (gas chromatography-mass spectrophotometry) - Carnitine (plasma, urine, total, free) - Free fatty acids, very long chained fatty acids - Orotic acid (urine) - Galactose-1-phosphate uridyl transferase (Beutler test) Tissue enzymes, DNA investigations (leukocytes, liver, fibroblasts)