Risk calculations for cystic fibrosis in neonatal screening by immunoreactive trypsinogen and CFTR mutation tests.

Abstract

Although neonatal screening (or newborn screening) for cystic fibrosis (CF) is commonly practiced, systematic methods for accurate risk calculations are currently lacking. We evaluated characteristics of the immunoreactive trypsinogen (IRT) test using the published data. The probability that a neonate has a positive IRT test, if the neonate is affected, a carrier, or a noncarrier, is approximately 1, 0.041, or 0.011, respectively. We provide methods to calculate genetic risks for a variety of commonly encountered scenarios in which neonates are positive by the IRT test. Our Bayesian methods permit CF disease probabilities to be calculated accurately, taking into account all relevant information.