Carrier detection in cystic fibrosis.

We evaluated four methods purported to distinguish between individuals homozygous or heterozygous for cystic fibrosis (CF) and normal controls: (1) detection of a protein in the serum by isoelectric focusing at pH 8.5, (2) detection of a lectinlike factor in the serum by hemagglutination, (3) isolation of CF-lectin from the serum by affinity chromatography, and (4) measurement of MUGB-reactive proteases in the plasma. The results were disappointing. The detection of CF protein by isoelectric focusing was unreliable; it could be identified in only 46% of heterozygotes and 66% of homozygotes, with a false positive rate of 17%. Detection of a lectinlike factor by hemagglutination was also found to be unreliable and irreproducible. The lectin isolated by affinity chromatography was not specific for the CF gene. No significant differences were found in the MUGB titers of the three populations tested. However, low titers (MU less than 200 nmol/ml) were found in 33% of homozygotes and heterozygotes and in 17% of normal controls. We conclude that none of these methods is suitable for carrier detection in cystic fibrosis.