Letter: Serum alpha-fetoprotein in cystic fibrosis.

Over the past 12 months we have examined by both counterimmunoelectrophoresis and 
radioimmunoassay sera from (a) 37 patients with cystic fibrosis (age 6 
months to 17 years), (b) 10 of their siblings, and (c) 
24 of their parents for the presence of raised serum levels 
of AFP. By counterimmunoelectrophoresis we were unable to detect an increased 
serum concentration of AFP in any of the cystic fibrosis patients 
or their relatives. In addition, the results from the radioimmunoassay method 
showed that all of the cystic fibrosis patients and their relatives 
had normal concentrations of AFP in their serum. - Using a 
double antibody radioimmunoassay we found the mean serum AFP for seven 
children with cystic fibrosis to be little different from that of 
controls, while all seven values fell within the normal range for 
this series. - In seven patients considered to have cystic fibrosis 
on the basis of a sweat chloride level above 65 mmol/l 
the mean serum alpha-fetoprotein (AFP level was 1825 (range 130 - 
2360) microg/l. The corresponding level in the patients was 433 (range 
80 - 1055) microg/l. Drug therapy given to these patients may 
have a subtle hepatoxic influence, thereby causing a rise in AFP 
levels. The severity of the disease does not influence the degree 
of elevation. There is a corresponding rise in carcinoembryonic antigen levels 
also, but the latter is related to the degree of tissue 
damage and results from the sero-cross-reactivity between mucus-producing respiratory mucosa and 
fetal tissues. 