Elevated IRT levels in African-American infants: implications for newborn screening in an ethnically diverse population.

During the first 4 years of newborn screening (NBS) for Cystic Fibrosis (CF) in New York there was a statistically significant, twofold greater relative risk of an Immunoreactive Trypsinogen (IRT) level greater than 95% in African-American infants. The reason for this previously reported increase in IRT level in African-American infants is unclear. The positive predictive value of a screen positive result in this population was only 0.3%. The bulk of screen-positive African-American infants were in the top 0.2% (IRT) group, with no CF mutations isolated. Repeat IRT testing at 2-3 weeks of age may represent a suitable approach to decrease the false-positive rate in this population.