Testing of maternal sera in pregnancies at risk for neonatal alloimmune thrombocytopenia

The utility of prenatal testing of maternal serum for platelet-reactive antibody was assessed in 25 women at risk of delivering infants with neonatal alloimmune thrombocytopenia (NAT). Seventeen women were incompatible with their husbands for the PlA1 antigen and three for Baka; in five families, no demonstrable platelet-specific antigen incompatibility was found. Analysis of the clinical outcome demonstrated that women with platelet-specific antibody detectable in any of the assays at any time during gestation were at risk of delivering thrombocytopenic infants (neonatal platelet count 31,250/microliters if mother did have antibody, as compared with 138,750/microliters if she did not; p less than 0.005). When only PlA1-incompatible pregnancies were examined, this association remained significant (mean neonatal platelet count in infants exposed to anti-PlA1, 34,285/microliters; that in infants not so exposed, 243,000/microliters; p less than 0.001). Changes in antibody strength throughout pregnancy did not correlate with the severity of NAT. The combination of the antigen-capture enzyme-linked immunosorbent assay and the indirect immunofluorescence test appeared to be most sensitive in detecting relevant platelet-specific alloantibodies. It is concluded that the detection of platelet-specific alloantibody in maternal serum in pregnancies at risk for NAT predicts moderate to severe NAT. However, the failure to detect such antibody does not always predict a normal neonatal platelet count.     

A prospective, randomized study of the use of platelet concentrates irradiated with ultraviolet-B light in patients with hematologic malignancy

BACKGROUND: Irradiation of platelet concentrates (PCs) with ultraviolet- B (UVB) light inactivates the contaminating white cells and might be an alternative to filtration for the prevention of alloimmunization to HLA antigens and subsequent refractoriness to further platelet transfusions in multiply transfused patients with bone marrow failure. STUDY DESIGN AND METHODS: Patients with hematologic malignancy, mainly acute myeloid leukemia, were prospectively assigned in a random manner to receive either UVB-irradiated or control, nonirradiated PCs. All patients were given red cells that were white cell reduced by filtration. Transfusion efficacy and alloimmunization were assessed by means of corrected count increments, requirement for red cells and PCs, and measurement of lymphocyte-reactive antibodies. RESULTS: UVB-irradiated PCs had a clinical efficacy similar to controls as judged by corrected count increments at 1 to 6 and 12 to 24 hours and by the median requirement for red cell and platelet transfusions. Alloimmunization determined by measurements of lymphocyte-reactive antibodies using both conventional and antiglobulin-augmented lymphocytotoxicity techniques was not abolished in recipients of UVB-irradiated PCs (4/30, 13%) but was less than that in controls (5/20, 25%; p = NS). The mean number of platelet transfusion episodes prior to the occurrence of alloimmunization was greater in the control group (27 vs. 10; p = 0.017). CONCLUSION: In this trial, UVB irradiation did not diminish the clinical efficacy of platelet transfusions. There was a small but nonsignificant reduction alloimmunization, but no difference in refractoriness of the two groups was observed. Larger prospective randomized studies are required to confirm these findings and to compare UVB irradiation with white cell reduction.     

In vitro and in vivo persistence of reticulocytes from donor red cells

BACKGROUND: Reticulocytes are important in the phenotyping of transfused patients. Reticulocytes can persist in blood units for the shelf life of the unit. STUDY DESIGN AND METHODS: Temperature dependence of reticulocyte persistence was examined in vitro at 4, 24, and 37 degrees C by using thiazole orange staining and flow cytometric analysis. Two-color flow cytometric analysis was used to evaluate the persistence of donor reticulocytes in transfused patients. RESULTS: Flow cytometric analysis using thiazole orange demonstrated that persistence of reticulocytes in units of stored CPDA-1 blood was temperature-dependent. Reticulocytes disappeared over 13 and 6 days at 24 degrees C and 37 degrees C, respectively, but at 4 degrees C the reticulocyte count changed little over 35 days. Two-color flow cytometric analysis of reticulocyte antigens was used to follow donor reticulocytes in 14 transfusion events in nine different patients. Donor reticulocytes persisted through 24 hours in 75 percent of the patients and were detectable at 48 hours in three patients. CONCLUSION: This study demonstrates that reticulocytes persist during refrigerated storage; they are detectable in the circulation of most recipients for the first 24 hours after transfusion and in the circulation of a few recipients after 48 hours. These findings may have relevance for separation techniques based on reticulocyte density in samples drawn shortly after transfusion and for evaluation of reticulocyte counts in patients with hematologic abnormalities.