This screening test is used in the evaluation of patients suspected of having one of the mucopolysaccharidoses, including Hurler (MPS IH), Scheie (MPS IS), Hunter (MPS II), Sanfilippo (MPS III), Morquio (MPS IV), Marteaux-Lamy (MPS VI) and Sly (MPS VII) syndromes. Mucopolysaccharides (MPS) are extracted from urine and fractionated using high-performance thin-layer chromatography (TLC). Specific mucopolysaccharides including keratan, heparan, dermatan and chondroitin sulfates are visualized following staining with toluidine blue. Abnormal results should be followed up with specific diagnostic enzyme testing. Clinical history should be provided to the laboratory for optimal interpretation of results.