Abstract
A study was made of oxalated umbilical vein blood of nearly every infant born at The Mount Sinai Hospital in a nine month period. A specimen of maternal blood was available for intragroup antibody screening and six cases of Rh-Hr hemolytic disease were eliminated from the data. The umbilical vein blood was tested, where possible, for: (1) group and Rh, (2) direct antiglobulin test, (3) hemoglobin, (4) reticulocyte count and examination of red cell morphology, (5) plasma bilirubin, and (6) osmotic fragility in 0.52 per cent NaCl. From the mothers’ blood groups, the infants were classified into group compatible and group incompatible, and the arithmetic means of the hemoglobin, reticulocyte count, and plasma bilirubin obtained for each class. A third class of infants, those with positive direct antiglobulin test, were analysed separately for comparison.
1. A weakly positive direct antiglobulin test was obtained on the umbilical vein blood of over 11 per cent of group incompatible infants but in none of the group compatible infants.
2. It appears that the weakly positive direct antiglobulin test detects an abnormal class of group incompatible infants, since their mean hemoglobin is low, their mean reticulocyte count is high, and their mean bilirubin is high, when these means are compared with those of the other group incompatible infants.
3. Thirty-eight of thirty-nine mothers of incompatible infants with positive direct antiglobulin test were group O. In comparison with the distribution of the blood groups of the mothers of other incompatible infants, this disproportion is of significance.
4. The mean reticulocyte count of incompatible infants with negative direct antiglobulin test is slightly (but with statistical significance) higher than the mean reticulocyte count of compatible infants. This difference was found to be associated almost entirely with group O mothers.
5. Thirty-one out of thirty-eight infants with positive direct antiglobulin test had increased osmotic fragility in hypotonic NaCl. Two of the negative cases appeared to have slight spherocytosis on blood smear.
