The early laboratory diagnosis of mucopolysaccharidoses.

The early and accurate diagnosis of the mucopolysaccharidoses remains a problem for the clinical laboratory. Reported here is the systematic compari­ son of the ability of three common glycosaminoglycanuria screening proce­ dure (the Berry spot test, the AMES MPS® spot test, and the gross acid albumin turbidity test) to detect the mucopolysaccharidoses. These tests were run on random urine samples obtained from 34 well characterized cases of mucopolysaccharidosis representing nine different mucopoly­ saccharidosis types. A few random urine samples from normals as well as from selected individuals with other genetic diseases were also tested in the same manner. The Berry spot test with the 10 ¡A application of urine detected all 34 of the confirmed cases of mucopolysaccharidosis. One of 12 normals and six of eight of the other genetic disorders tested positively at this level. The AMES MPS® spot test failed to detect several Type IV and Type VI mucopoly­ saccharidoses, and the gross acid albumin turbidity test missed several Type III, Type IV, and Type VI cases. The failure of the gross acid albumin turbidity test to detect reliably the most frequently occurring Type III mucopolysaccharidoses, as well as the rarer Type IV and Type VI disorders, renders questionable the use of this procedure for glycosaminoglycanuria screening. The AMES MPS® spot test appears to be capable in detecting Types I, II, and III disorders. Also, this test affords less false positives than the Berry spot test. Unfortunately, it cannot be relied upon to detect the glycosaminoglycanuria found in Type IV and VI disorders. The Berry spot test clearly has the highest sensitivity; however, because of its low specificity, it is concluded that it is imperative that it be used in conjunction with additional urinary glycosaminoglycan analyses in order to establish definitively the presence of glycosaminoglycanuria.