An Assessment of the Differences in Erythropoiesis Between Transfused Males and Females with β Thalassaemia Major
Authors: Hapgood Greg , Walsh Timothy , Cukierman Ronit , Paul Eldho , Cheng Ken , Bowden Donald K 
Published: October 2019

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 1 Summary of patients included in the study Variable Overall Males Females p value Number 116 51 65 - Age (years) 39.3 ± 9.3 40.0 ± 9.6 38.8 ± 9.1 0.511 Weight (kg) 60.0 ± 11.6 64.9 ± 9.8 55.7 ± 12.4 < 0.0001 Height (cm) 159 ± 10.5 166 ± 8.3 153 ± 8.1 < 0.0001 Transfusion interval (weeks) 3.2 ± 0.6 3.2 ± 0.7 3.1 ± 0.5 0.168 No. RBC units per transfusion 3.03 ± 0.63 3.22 ± 0.76 2.89 ± 0.48 0.006 Estimated annual transfused volume (l) 13.5 (10.1-13.5) 14.0 (14.0-14.0) 14.0 (10.0-14.0) < 0.0001 Estimated annual transfused volume per kg (ml/kg) 215 (185-255) 202 (185-225) 225 (188-263) 0.028 Estimated patient blood volume (l) 3.79 ± 0.73 4.39 ± 0.50 3.32 ± 0.52 < 0.0001 Ratio 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) < 0.0001 Splenectomy 49.5% 61% 40% 0.031

Data 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 2. Laboratory indices of pre-transfusion erythropoiesis for all patients Variable Overall Male Female p value Hemoglobin (g/l) 98 ± 8.9 98 ± 9.9 99 ± 8.1 0.36 Red cell count (x 1012/l) 3.4 ± 0.35 3.45 ± 0.40 3.50 ± 0.32 0.46 Ferritin (mcg/l) 821 (604-1300) 754 (582-1139) 943 (639-1356) 0.11 Erythropoietin (mIU/ml) 58 (37-99) 72 (41-149) 52 (35-89) 0.006 Manual NRBC (number NRBC/100 WBC counted) 6 (1-54) 21 (2-98) 3 (1-28) 0.003 Automated NRBC (number NRBC/100 WBC counted) 5 (0-34) 17 (0-54) 1 (0-20) 0.014

Data are mean ± standard deviation or median (interquartile range).

Disclosures

No relevant conflicts of interest to declare.