Proteus vulgaris agglutination by cystic fibrosis sera.

The factor in sera of patients with cystic fibrosis (CF) and their parents which agglutinates Proteus vulgaris has characteristics similar to those of IgG antibody to this organism. Sera of patients without CF who have P. vulgaris infections agglutinate the organism similarly. At present there are too many false-positives in a control population for the test to be widely useful for heterozygote identification.