No abstract

Conventional manual (enzyme and antiglobulin titres) and AutoAnalyser quantitation of anti-D sera were compared with the ability of the same sera to mediate lysis of Rh(D) positive red cells in an ADCC assay. AutoAnalyser (AA) quantitation correlated significantly with manual titration methods, although there were wide discrepancies between individual sera. The ADCC activity of the anti-D sera did not correlate with any of the conventional assays (AA, enzyme, antiglobulin). There were significant differences between anti-D sera obtained from females immunized during pregnancy and male volunteers immunized by deliberate injection. The female sera contained significantly less anti-D when assessed by AA, yet were significantly more active in ADCC activity at equivalent concentrations. These functional differences in anti-D activity could not be attributed to the absence of IgG subclasses (IgG1 and IgG3) known to induce ADCC. However, there was a relationship between ADCC and IgG1/IgG3 titres in that high ADCC activity was seen where the IgG3 titre was higher than the IgG1 titre. In the male anti-D sera IgG1 titres were greater than or equal to IgG3 titres and ADCC activity was very low.

This study identifies the benefit of using donor exposure rate (DER) to transfusion rate (TR) ratio as a discriminative index for assessing improvement in practice pattern in multiple-transfused neonates. It provides a methodology to demonstrate reduction in donor exposure that is not evident from the use of DER alone. Two time points, one 12-month period (1996-1997) before and one 12-month period (1999-2000) following the introduction of a paedipack system, were reviewed. Blood issued and wasted was quantified. The 1994 BSCH guidelines to define transfusion were used for both time periods, and recombinant erythropoietin (EPO) was not used. Following implementation of paedipack system, 186 donor units were made into satellite bags and kept for 35 days. A dramatic decrease in DER : TR ratio was noted for 79 transfused infants. The DER : TR ratio was 1 : 1 before and 1 : 3.2 after introduction of paedipacks, giving a 70.5% reduction in donor exposure risk. This was not evident from the use of DER alone, which remained the same (2.4) in the historical and study groups. High transfusions per donor unit (TPDU) correlated with the reduction in DER : TR ratio. Red cell wastage per transfusion was 190 +/- 30 mL before and 24.5 +/- 10 mL after intervention.

This article demonstrates a 62% reduction in the number of febrile nonhaemolytic transfusion reactions (FNHTRs) and 50% reduction in febrile reaction rate associated with red cell transfusions following graded introduction of universal leucodepletion. Though this is a statistically significant reduction (P = 0.009), it shows limited efficacy in abrogating this complication. We also found a reduction in the proportion of cases of FNHTRs with lymphocytotoxic antibodies over the period studied from 54% in 1998, 28% in 1999 to 23% in 2000. This corresponds to a relative increase in the number of febrile reactions without human leucocyte antigen (HLA) antibodies following full implementation of universal leucodepletion, as the total number of reported reactions actually fell considerably during the period. The increase in the number of cases without HLA antibodies was directly proportional to the increase in the number of leucodepleted units used.

An in vitro test system is described which measures the ability of anti-D sera to lyse Rh(D)-positive red cells. This test was applied to anti-D sera from 11 cases of HDN selected in Glasgow and tested ‘blind’ in Edinburgh. Evidence is presented to support the view that the ADCC (antibody-dependent cell-mediated cytotoxity) assay can correctly identify those cases where there is a satisfactory clinical outcome despite a high level of anti-D suggesting otherwise. Amniocentesis might therefore be avoided in this group.