Prenatal diagnosis of cystic fibrosis: False negative result with the 4-methylumbelliferyl-p-guanidinobenzoate assay for proteases in amniotic fluid
✍ Scribed by J. R. Green; M. J. Lentze; E. Rossi; D. Sidiropoulos; G. Schubiger
- Publisher
- Springer
- Year
- 1982
- Tongue
- English
- Weight
- 465 KB
- Volume
- 139
- Category
- Article
- ISSN
- 0340-6997
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✦ Synopsis
The promising method for the prenatal detection of cystic fibrosis (CF), developed by Nadler's group [6,7], has recently attracted considerable interest but there is a lack of confirmatory reports from other laboratories. We have established the assay for methylumbelliferyl-guanidinobenzoatereactive proteases (MUGB assay) and used it, together with isoelectric focusing and gel filtration, to screen retrospectively 84 second and third trimester amniotic fluids, one of which was known to be from a CF pregnancy.
The control values for MUGB-reactive protease were 4.25 + 1.36 and 6.12 _ 1.04 nmoles/mg protein (mean --4-_ 1 SD) for second and third trimester fluids, respectively, compared to 5.64 nmoles/mg protein for the third trimester CF fluid. Gel filtration resolved two peaks of MUGB-reactive protease of approximately 50000 and 10 000 molecular weight from all samples. Insufficient CF fluid remained for isoelectric focusing and the results obtained with normal amniotic fluids were inconclusive due to a highly variable background staining. Thus, with two methods a false-negative result has been obtained, suggesting that further refinement of these techniques may be required before they can be routinely applied for the prenatal diagnosis of CF.