Prenatal diagnosis of cystic fibrosis [letter].

As far as I know, no test for the prenatal diagnosis of 
cystic fibrosis has yet been shown to be reliable, but several 
experimental studies on prenatal diagnosis of cystic fibrosis are being carried 
out. Deficient protease activity, assayed by 4-methylumbelliferyl guanidinobenzoate, an active site 
titrant of serine proteases, has been reported in plasma and cultivated 
skin fibroblasts from patients with cystic fibrosis. Another prenatal diagnostic test 
for cystic fibrosis involves the observed resistance of patients' skin fibroblasts 
to dexamethasone (a synthetic glucocorticoid) toxicity, in comparison to normal fibroblasts. 
Specific induction of alkaline phosphatase with Tamm Horsfall glycoprotein, isoproterenol and 
theophylline has been recorded in skin-derived fibroblasts from affected patients. 