Bilirubin crystals in peripheral blood smears from neonates with unconjugated hyperbilirubinaemia

Peripheral blood smears from 118 hyperbilirubinaemic neonates and 10 neonates with physiological jaundice were screened for the presence of bilirubin crystals. Smears were made from EDTA anticoagulated blood from 107 hyperbilirubinaemic neonates and capillary blood from 11 cases. In sixty-three (58.8%) of the 107 EDTA smears, yellow-coloured refractile rhomboid crystals were seen within the cytoplasm of the neutrophils, band forms, metamyelocytes, myelocytes, monocytes, and also extra-cellularly. The mean serum unconjugated bilirubin value was significantly higher (293.8 mumol/l) in neonates with crystals in their smears as compared to those without crystals (242.2 mumol/l). In septicaemic neonates the proportion of neutrophil-containing crystals was higher than in the case of other aetiological factors responsible for unconjugated hyperbilirubinaemia. None of the smears made from non-anticoagulated capillary blood showed bilirubin crystals.