Is cystic fibrosis protein a diagnostic marker for individuals who harbor the defective gene? [letter].

It has been almost 5 years since the publication of our original 
report describing a "cystic fibrosis factor" (now designated "cystic fibrosis protein" 
or CFP) detected in the serum of most homozygotes and heterozygotes 
for cystic fibrosis when analyzed using isoelectric focusing in thin layer 
polyacrylamide gels. The recent report by Scholey et al. confirms that 
CFP is present in the majority of CF sera and that 
it can be detected by our methods. Before discussing whether the 
CFP can be used as a diagnostic marker for cystic fibrosis, 
we would like to examine more closely some of the requirements 
of the method which seemed to have been critical for the 
detection of CFP by Scholey et al. We would like to 
point out that Scholey and his coworkers adhered closely to most 
of our guidelines during their attempts to detect CFP. The exact 
nature of CFP and the other ciliary dyskinesia factors is only 
partially known, and all aspects of their metabolism are not yet 
understood. Therefore, it may be some time before we comprehend the 
incomplete concordance found between CFP and the pathogenesis of CF. 