Letter: False-negative meconium tests for cystic fibrosis.

Two reviews have questioned the value of meconium tests for the routine 
screening of cystic fibrosis because of the high proportion of false-positive 
and (perhaps more importantly) false-negative results. We wish to report our 
findings on false-negative results. We are evaluating various methods of meconium 
screening including the Boehringer Mannheim test strip, a semiquantitative test for 
proteins, electroimmunoassay of albumin, and estimation of the albumin/alpha1-antirypsin ratio. The 
figures are too small to draw any conclusions between the apparent 
relationship of false-negative results and a family history of the disease, 
but we feel that the results illustrate that little reliance should 
be put on a negative meconium test. This is not to 
say that the meconium test is valueless. In our study, at 
least 40% of infants with cystic fibrosis had a positive meconium-test 
result but did not have meconium ileus and thus the possibility 
of cystic fibrosis in these infants was recognised within a few 
days after birth and usually well before definitive clinical signs of 
the disease were manifest. 