[The importance and limits of laboratory tests for evaluating the transplacental passage of fetal erythrocytes into the maternal circulation].
The KBB acid elution test is used to assess the presence and extent of transplacental passage of fetal cells into the maternal circulation both as a diagnostic aid in detecting hemorrhage before birth and in monitoring pregnancies at risk for hemolytic disease of the newborn. However the technique is ineffective when an hereditary Hb-pathy with associated increase in HbF is present in the mother, like the HPFH, delta-beta thalassemia and other hereditary abnormal hemoglobins. A mother with HPFH and another mother with delta-beta thalassemia with false positive result of the acid-elution test are described and the need for an extension of the clinical and laboratory study in families with hereditary HbF disorder is stressed.