Distribution of serum amylase isoenzymes in cystic fibrosis homozygotes and heterozygotes.

A simple method has been elaborated for the routine separation and quantitative determination of amylase isoenzymes. The ratio P/S, the quotient of the activity values obtained by densitometric evaluation of the pancreatic and salivary isoenzymes, is used to characterize their distribution. In healthy adults and children the value for P/S is above 1 in 80% of the cases, with a mean of 1.87 +/- 0.23. In 90% of heterozygote CF gene-carriers, the P/S is below 1 with a mean of 0.68 +/- 0.13. In addition to the higher total amylase activity, in MV homozygote patients P/S is less than 0.1, and even 0.001. The phenomenon is explained by a compensatory enhancement of salivary activity. The method is a suitable diagnostic test of the exocrine function of the pancreas and for evaluation of the serum amylase isoenzymes. The P/S value allows to differentiate heterozygote CF gene-carriers from homozygotes and healthy individuals.