An Assessment of the Differences in Erythropoiesis Between Transfused Males and Females with β Thalassaemia Major

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▪Background: β thalassemia major results in ineffective erythropoiesis. Blood transfusion aims, in part, to suppress this and to limit morbidity from anaemia, bone marrow expansion and extra-medullary hemopoiesis (EMH), thereby increasing survival. According to current international guidelines, males and females are transfused equally.Aims: We sought to assess the adequacy of suppression of erythropoiesis in all 126 transfused adult (>18 years) males and females with β thalassemia major at our centre by: (1) assessing readily available pre-transfusion indices of erythropoiesis, including erythropoietin (EPO) levels; (2) determining the volume of blood transfused per kilogram (kg) and per calculated blood volume; and (3) assessing the incidence of para-spinal EMH masses based on magnetic resonance imaging (MRI).Methods: We analysed pre-transfusion (i.e., the day of transfusion) hemoglobin (Hb), reticulocyte count, red blood cell count (RCC), nucleated red blood cell (NRBC) count, EPO and ferritin levels in patients receiving stable, regular blood transfusion. Automated and manual NRBC and reticulocyte enumerations were performed. Blood volume was calculated using Nadler’s formula. MRI performed to assess cardiac function and hepatic and cardiac iron loading was reviewed for the presence of para-spinal EMH.Results: One hundred and sixteen adult patients (51 males and 65 females) provided pre-transfusion blood samples (Table 1). The 10 patients not included were either not available or declined testing. The mean pre-transfusion Hb was 98-99g/l with no difference between males or females (Table 2). Therefore, our data reflect long-standing adherence to current international transfusion recommendations. EPO levels and NRBC count (manual and automated) were significantly higher in males compared to females. RCC, reticulocyte count (manual and automated) and ferritin levels were not different between males and females. Males received less blood per kg of body weight and per calculated blood volume. The incidence of para-spinal EMH was 13% (14/110) and was significantly higher in males (11/50) compared to females (3/60)(22% versus 5%, respectively, (p = 0.01)). The incidence of splenectomy was higher in males.Conclusions: These findings confirm that erythropoiesis is not equally suppressed in males and females and that males are more prone to complications from being under-transfused with current transfusion practices. This work has major clinical implications for transfusion practices in the management of β thalassemia major.Abstract 4045. Table 1Summary of patients included in the studyVariableOverallMalesFemalesp valueNumber1165165-Age (years)39.3 ± 9.340.0 ± 9.638.8 ± 9.10.511Weight (kg)60.0 ± 11.664.9 ± 9.855.7 ± 12.4< 0.0001Height (cm)159 ± 10.5166 ± 8.3153 ± 8.1< 0.0001Transfusion interval (weeks)3.2 ± 0.63.2 ± 0.73.1 ± 0.50.168No. RBC units per transfusion3.03 ± 0.633.22 ± 0.762.89 ± 0.480.006Estimated annual transfused volume (l)13.5 (10.1-13.5)14.0 (14.0-14.0)14.0 (10.0-14.0)< 0.0001Estimated annual transfused volume per kg (ml/kg)215 (185-255)202 (185-225)225 (188-263)0.028Estimated patient blood volume (l)3.79 ± 0.734.39 ± 0.503.32 ± 0.52< 0.0001Ratio of estimated annual transfused volume (l) per estimated patient blood volume (l)3.33 (2.84-4.01)2.98 (2.68-3.28)3.79 (3.3-4.35)< 0.0001Splenectomy49.5%61%40%0.031Data are mean ± standard deviation, median (interquartile range) or percentage. Transfused volumes are calculated on the assumption that each unit contains 260ml red cells (Australia Red Cross Blood Service red cell unit mean volume = 259 ± 23ml). Nadler’s formula for total blood volume (TBV): men TBV (ml) = 604 + (367 x height3(m3)) + (32.2 x weight (kg)); women TBV = 183 + (356 x height3(m3)) + 33.1 x weight (kg)).Table 2Laboratory indices of pre-transfusion erythropoiesis for all patientsVariableOverallMaleFemalep valueHemoglobin (g/l)98 ± 8.998 ± 9.999 ± 8.10.36Red cell count (x 1012/l)3.4 ± 0.353.45 ± 0.403.50 ± 0.320.46Ferritin (mcg/l)821 (604-1300)754 (582-1139)943 (639-1356)0.11Erythropoietin (mIU/ml)58 (37-99)72 (41-149)52 (35-89)0.006Manual NRBC (number NRBC/100 WBC counted)6 (1-54)21 (2-98)3 (1-28)0.003Automated NRBC (number NRBC/100 WBC counted)5 (0-34)17 (0-54)1 (0-20)0.014Data are mean ± standard deviation or median (interquartile range). DisclosuresNo relevant conflicts of interest to declare.