Assessing suitability of the AbsoluteIDQ p180-kit from Biocrates for analysis of the metabolism of peroxisomal disorders, we compared serum samples of 17 ZSS patients with PEX1 mutations to a non-affected age-matched control group, as well as 36 X-ALD patients with mutations in the ABCD1 gene and two DPBIII patients with mutations in the HSD17B4 gene. The gene discussed is PEX1; the disease is peroxisomal disease.