YIELD OF RETICULOCYTE COUNTS AND BLOOD SMEARS IN TERM INFANTS

Reticulocyte counts and blood smears are commonly recommended to evalu ate jaundice in newborns. To investigate the results and diagnostic yi eld of these tests, we reviewed a computerized database and medical re cords of term newborns who had reticulocyte counts (n = 799) or blood smears (n = 781) within the first week after birth at two hospitals. N early a threefold difference was noted in reticulocyte counts between the two hospitals (median 8.0% vs 2.8%; P<.0001), apparently due to di fferences in laboratory methods. Among the patients with ''abnormal'' reticulocyte counts or blood smears (n = 192), isoimmunization was dia gnosed in 54, presumed hemolysis of unknown etiology in two, G6PD defi ciency in one, and pyropoikilocytosis in one. We conclude that better standardization of reticulocyte counts is needed. When ordered as scre ening tests for hemolysis in jaundiced infants, reticulocyte counts an d blood smears seldom lead to diagnoses of hemolysis other than isoimm unization.