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Tandem mass spectrometry can be used to identify newborn babies who may have a metabolic disease. This technique measures the amount of amino acids and other substances to detect any unusual amounts that could be caused by a metabolic disease. However, many of these babies would have no symptoms and it is not clear whether they would ever develop symptoms.

Cystic fibrosis is a genetic disease which causes the secretions of the body to be thick and consequently difficult to eliminate. As a result of this, the lungs are often severely affected. Cystic fibrosis occurs when an infant receives a defective gene from both parents; the condition is classified as a Mendelian dominant genetic disorder. The exact gene which causes cystic fibrosis was recently located on the long-arm of chromosome 7. The ability to test for such irregularities of the chromosomes of infants is relatively difficult and expensive. A system which uses an immunologic test of dried blood (an immunoreactive test) taken from newborns is commonly used to screen babies for the presence of cystic fibrosis. The test assesses the level of blood pancreatic isoamylase (an enzyme produced by the pancreas and required to metabolize starch) as an index of pancreatic enzyme production. Recent concerns about this method have been raised in the case of cystic fibrosis babies who have relatively normal pancreatic function. The present study associates the level of pancreatic functioning with the results of blood screening for cystic fibrosis. The diagnosis of cystic fibrosis is confirmed by a standard test called the sweat test. Ninety-eight infants who were identified by the blood test as having cystic fibrosis were referred to the study and 78 ultimately participated. Of these children, 37 percent had nearly normal pancreatic measures which were assessed by various physiologic means other than blood enzymes. This study demonstrates that the immunoreactive test is able to identify cystic fibrosis children who maintain pancreatic functioning (approximately 37 percent of children). At present it is not possible to identify the rate of false negative results of patients who have adequate pancreatic functioning. (Consumer Summary produced by Reliance Medical Information, Inc.)