The use of leukocyte-depleted blood components has become the standard therapy for multiply transfused patients during the past few years, as a measure to reduce the frequency of alloimmunization and refractoriness. We assessed frequency and causes of refractoriness, defined as a repeated 24-h post-transfusion platelet count below 20,000/microliters, in 145 consecutive patients who received three or more single-donor platelet concentrates during a 1-year period. Flow-cytometric detection of anti-platelet antibodies and a glycoprotein-specific ELISA were applied for the diagnosis of alloimmunization. Forty patients (27.6%) had at least one episode of refractoriness. In 25 of these 40 patients (62.5%), nonimmune factors (fever, sepsis, coagulopathy, splenomegaly) alone were the cause. In 15 refractory patients alloantibodies were detected. In seven patients (17.5%), alloimmunization alone caused an inadequate transfusion response, while in eight refractory patients (20.0%) alloimmunization and fever or sepsis were present. HLA antibodies were detected in 17 patients (11.7%); three patients (2%) had platelet-specific antibodies in addition to HLA antibodies; in two patients panreactive platelet antibodies were detectable. All 17 patients had a history of previous transfusions or pregnancy. We did not observe primary immunization in patients transfused exclusively with filtered (leukodepleted) blood products. Our data suggest that alloimmunization in patients with a negative risk history can be prevented by the exclusive use of leukodepleted blood components.

This study compares the feasibility of single-donation HCV RNA screening, with the detection of a relatively high percentage of window-phase donations, to data reported from groups using HCV RNA testing of plasma pools. The relative yield of NAT of individual donations versus minipools should be directly investigated in the near future.

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We report on flow cytometric IgG subclass determinations of red cell antibodies using polyclonal FITC-labeled antibodies. The limit of detection of this method was 1 ng anti-D per 1 x 10(7) red cells. The inter- and intra-assay coefficients of variance were 8.2 and 2.3%, respectively. In 8 newborns with a positive direct antiglobulin test (DAT) in the gel centrifugation test (GCT), due to ABO antibodies, IgG1 was detected in all and IgG2 additionally in 4 of these cases. In 5 severe cases of hemolytic disease of the newborn (HDN) due to anti-D, large amounts of IgG1 were found, and in 3 of these 5, IgG3 in combination with IgG1. In 8 mild or moderate HDN cases (4 anti-D, 2 anti-E, 1 anti-Fya, 1 anti-Jka), phototherapy sufficed, and IgG1 was the only antibody. In 7 adult patients with malignant lymphoma and a positive DAT (GCT), only small amounts of IgG1 red cell autoantibodies could be demonstrated by flow cytometry. In 5 further patients with malignant lymphoma, a positive DAT, and severe hemolytic anemia, large amounts of IgG1 autoantibodies were found and IgG3 was also present in 3 of these cases. Flow-cytometric determination of IgG subclasses may be a useful tool in immunohematology, since subclass determinations were possible in all of these cases. This method is suited for clinical routine and offers the possibility of sufficient standardization.

LRS apheresis appears to be a safe procedure, which produced effective PCs with few contaminating leukocytes. With new apheresis technology, filtration of PCs may become superfluous.