Prenatal diagnosis of cystic fibrosis. Analytical evaluation of microvillar enzyme determinations in amniotic fluid.

The activity of gamma-glutamyltranspeptidase and total alkaline phosphatase and its isoenzymes has been determined in 261 amniotic fluid samples taken from pregnant women with known normal outcome and in 30 amniotic fluid samples from pregnant women with a 1:4 risk for cystic fibrosis (CF). Preliminarily, 114 amniotic fluid samples were assayed in parallel in three different laboratories, and a good correlation was found even though different assays were used. From the results obtained in control amniotic fluids, normal range and CF-predictive cutoff values were established. No false-negative results were found in this study. Among the predicted affected pregnancies 7 were terminated, and 3 went to term: 1 resulting in a CF-affected child and the other 2 in healthy children. CF was confirmed in all the aborted fetuses. In 1 case the results were inconclusive. In this study numerical results obtained for samples with a 1:4 risk of CF analyzed in the three laboratories were always virtually identical.

The assay of chymotrypsin in stool as a simple and effective test of exocrine pancreatic activity in cystic fibrosis.

The study evaluates two methods of assay of fecal chymotrypsin (titrimetric and spectrophotometric method) as an index of exocrine pancreatic function. The assay was performed on 101 control subjects and 128 cystic fibrosis (CF) patients by the first method, and 75 controls and 102 CF patients by the second method. CF subjects were subdivided into four groups based on pancreatic function: total pancreatic insufficiency in the first group, partial pancreatic insufficiency in the second group, normal pancreatic function in the third group, and pancreatic insufficiency plus enzymatic treatment in the fourth group. Fifty-four CF patients were examined in the first group, 27 in the second group, 19 in the third group, and 28 in the fourth group by the titrimetric method; 23, 25, 50, and 65, respectively by the spectrophotometric method. The spectrophotometric method was highly reproducible and more sensitive and specific. With such a method the assay on stool random sampling correlated with the duodenal output of chymotrypsin after hormonal stimulation as well as fecal output of 72 h. The test had sensitivity and specificity of 100% if referred to CF patients with total pancreatic insufficiency. It was calculated that CF patients with normal fecal chymotrypsin have a probability of 76% to have a normal pancreatic function and a probability of 24% to have a partially compromised pancreatic function. The assay separates distinctly CF patients with a fat absorption coefficient greater than 90% from those with a coefficient less than 90%. The test is proposed for current clinical use in diagnosis and treatment of pancreatic insufficiency in cystic fibrosis.

The Km of NADH dehydrogenase is decreased in mitochondria of cystic fibrosis cells.

The kinetic properties of the NADH dehydrogenase of the mitochondrial respiratory chain, assayed as NADH-dependent rotenone-sensitive cytochrome c reductase have been studied in mitochondria isolated from mononuclear white blood cells in patients affected by cystic fibrosis. Data reported here show that the apparent Km of the enzyme for NADH is significantly decreased in cystic fibrosis mitochondria. These findings are independent of the age or the clinical state of the disease and have also been obtained with mitochondria isolated from cultured skin fibroblasts. These observations support the notion that cystic fibrosis is possibly accompanied by alterations of intracellular membranes and these are evident also in circulating cells and cultured fibroblasts.