A stable liquid control material for urinary enzyme assays.

A stable liquid control material for urinary enzyme assays was prepared by addition of ethylene glycol (30% v/v) or glycerol (30% v/v) to centrifuged urine, and pH adjustment to 7.0. Tested for 375 days, the material exhibited stable beta-N-acetylglucosaminidase, alanine aminopeptidase, gamma-glutamyltransferase and lactate dehydrogenase activities, at both 4 and -20 degrees C. The material further has been successfully evaluated in an external quality control program.