Alloimmunisation rates of sickle cell disease patients in the United States differ from those in other geographical regions.

OBJECTIVES: Comparison of the alloimmunisation rates of patients with sickle cell disease in the Unites States versus other countries. BACKGROUND: Sickle cell disease (SCD) patients treated with chronic transfusion therapy are at a high risk of red blood cell (RBC) alloimmunisation. MATERIALS AND METHODS: We reviewed published literature describing alloimmunisation rates of SCD patients. Average alloimmunisation rates and number of alloantibodies per transfused patient in the United States and other countries were evaluated. RESULTS: Twenty-four studies on alloimmunisation of SCD patients were found, 15 studies with 3,708 patients in the US and 9 studies with 2203 patients from other regions, including South America, the Caribbean, Middle East, Africa and Europe. The United States has a higher alloimmunisation rate (22·33 ± 0·13% versus 16·25 ± 0·35%, p < 0·0001) and a higher number of alloantibodies per transfused patient (0·45 ± 0·003 versus 0·20 ± 0·005, p < 0·0001) than other countries. Brazil with a higher proportion of multi-ethnic donors demonstrated a lower alloimmunisation rate compared to the United States (14·60 ± 0·40% versus 22·33 ± 0·13%, p < 0·0001) and fewer alloantibodies per transfused patient (0·20 ± 0·02 versus 0·45 ± 0·003, p < 0·0001) than the United States. CONCLUSION: SCD patients in the United States had a higher alloimmunisation rate, which could be reduced by a more ethnically diverse donor pool and a more conservative transfusion strategy in non-critical conditions.

A safe therapeutic apheresis protocol in paediatric patients weighing 11 to 25 kg.

BACKGROUND AND OBJECTIVES: Erythrocytapheresis and leukapheresis (LPE) of small children are logistically complex and many centres are reluctant to perform these procedures. In children, both sickle cell and leukaemic emergencies demand prompt action to prevent additional morbidity but detailed protocols for small children are lacking, and often are performed using guidelines shown to work in larger patients. We report a 3-year experience with children weighing 11-25 kg at a large academic medical centre. MATERIALS AND METHODS: All patients were treated with the COBE® Spectra apheresis system; circuit was primed with blood not adjusted for haematocrit and anticoagulant citrate dextrose A was used as anticoagulation. Procedures were performed in the paediatric intensive care unit by apheresis nursing staff. RESULTS: Twenty-five apheresis procedures in 19 patients were performed; 17 of 19 patients presented with sickle cell-related acute complications and two (2/19) with newly diagnosed acute leukaemia and hyperleucocytosis. None of the patients required medications during the procedures. Vital signs and clinical condition remained stable and did not worsen during or postapheresis. One patient had a delayed haemolytic transfusion reaction 1 week posterythrocytapheresis as he developed alloantibodies as a result of the procedure. All sickle cell patients achieved a target haematocrit of 21-30% and Haemoglobin A of ≥68%. Both leukaemia patients who underwent LPE had no further signs of leukostasis and achieved marked reductions in leucocyte counts. CONCLUSIONS: Apheresis of children weighing 11-25 kg can be safely performed without increased morbidity. We outline a protocol that can be used to perform apheresis with minimal complications.

Allergic transfusion reactions to platelets are more commonly associated with prepooled than apheresis components.

BACKGROUND AND OBJECTIVES: Transfusions of pooled or apheresis platelets are seen as equally effective in increasing platelet counts with similar rates of transfusion reactions. It has been suggested that allergic transfusion reactions (ATRs) to platelets are associated with recipient and donor factors. In this study, we assessed differences in ATR rates among individuals who received platelet components at two academic medical centres. MATERIALS AND METHODS: A total of 45 189 leukoreduced platelet products were transfused during the study period of which 31 748 were apheresis units and 13 441 were pooled units. RESULTS: Transfusion reactions were reported in 0·6% (277 of 45 189) of platelet transfusions. The reaction rate was significantly higher in pooled (102 of 13 441) than in apheresis (175 of 31 748) (0·76% vs. 0·55%, respectively, P = 0·01) components. However, an analysis of reactions by categories indicated that only the ATR rate was significantly higher in pooled (55 of 13 441) products as compared with apheresis (76 of 31 748) (0·41% vs. 0·24%, respectively, P = 0·0029) platelets. Moreover, there was no difference in the rate of ABO mismatch between pooled and apheresis products. CONCLUSION: Our data indicate that pooled platelet components are associated with higher ATR rates than apheresis platelets, suggesting that these components may not be completely equivalent from the standpoint of adverse events. Further investigation is needed to address whether differences in ATRs are related to the pooling process or the extent of donor antigen exposure.