Serum trypsin inhibitory capacity and the idiopathic respiratory distress syndrome

Alpha-1 antitrypsin, alpha-2 macroglobulin, and total trypsin inhibitory capacity levels were significantly lower in the umbilical cord serum of newborn infants with idiopathic respiratory distress syndrome (IRDS) than in weight-matched control subjects. Levels were unrelated to gestational age or sex. Sequential serum samples were drawn in 17 infants with IRDS; there was a tendency for levels of total trypsin inhibitory capacity to increase in 6 of 9 survivors. In contrast, 7 of the 8 infants who died had persistently low levels and some had further decreases in concentration. In amniotic fluid obtained at 12 to 22 weeks' gestation in cases not related to IRDS, alpha-1 antitrypsin and total trypsin inhibitory capacity could usually be detected but alpha-2 macroglobulin was not. Serum enzyme inhibitor levels may be of diagnostic significance in IRDS.