A new diagnostic technique for adenylosuccinate lyase deficiency.

A convenient and simple method of diagnosing adenylosuccinate lyase (ASL) deficiency is described. This method consists of (1) isolation of SAICA riboside and S-Ado with a cation exchange resin; (2) measurement of the UV absorbance of the ammonia eluate at 270 and 250 nm; (3) calculation of the A270/A250 ratio. If the value of this ratio is less than 0.