High serum immunoreactive trypsin not caused by cystic fibrosis

Editor—In the course of neonatal screening for cystic fibrosis, a boy had raised immunoreactive trypsin values 112 pg and 73 μg/l (normal reference values <70 μg/l) at 6 and 28 days of age. His birthweight had been 3.6 kg (50th centile) at 41 weeks of gestation, and at 6 weeks his weight was 3.77 kg (< third centile). His length was 54 cm (25th centile) and …