Elevated meconium lactase activity. Its use as a screening test for cystic fibrosis

Screening of newborn infants could provide information needed to evaluate the effects of early treatment on the course and prognosis of cystic fibrosis (CF). Two procedures of screening meconium for CF were compared: increased albumin levels, detected by a commercial test strip; and increased lactase activity, detected by glucose production after incubation of meconium with lactose. Specimens positive by the lactase test were retested for albumin. Low-birth-weight infants accounted for more than half the positive test results with both procedures. Sweat chloride measurements were carried out only on infants whose meconium specimens had albumin concentration greater than 12 mg/g (wet weight), measured by radial immunodiffusion. Twelve infants with CF were identified through screening, six while testing 44,816 specimens by lactase activity test. Three additional infants with CF were missed because meconium specimens were negative to both tests.