Detection of cystic fibrosis homozygotes and heterozygotes with plasma.

Evidence is accumulating which indicates that the basic defect in cystic fibrosis interferes with the formation of recognition markers on hydrolytic enzymes. As a result these hydrolases leak into the extracellular space and some of them display abnormal thermolabilities. By heat inactivation of plasma alpha-mannosidase at 41 degrees C and plasma phosphatase at 36.5 degrees C, both enzymes being assayed at pH 5.4, it is possible to differentiate normal people from cystic fibrosis carriers and patients.