CFTR and intestinal obstruction in the newborn due to guanylate cyclase 2C deficiency: Among 7 children with false-negative CF screening results, 4 had an IRT value within the expected range, 2 had PAP values within the expected range (including 1 case with meconium ileus), and in 1 child, both disease-causing mutations were absent from the candidate gene panel while fail-safe was negative.