The role of the laboratory in the diagnosis of cystic fibrosis.

Laboratory investigations used for detecting cystic fibrosis have been critically reviewed. The sweat test is still the only investigation that can be used for detecting the disease at any age. Trypsin in blood or serum might have the same discriminatory power during the first three months of life and could be used for neonatal screening. There is no immediate prospect for prenatal diagnosis or heterozygote detection. The change of the pattern of plasma proteins in cystic fibrosis is the same as in other chronic disorders with varying clinical intensity. Albumin and alpha-1-antitrypsin may be used to monitor treatment. The plasma concentration of alpha-2-macroglobulin is considerably decreased in many younger patients.