Participant characteristics
Fifteen male (41%) and twenty-two female adolescents were included in the study. Participant characteristics are shown in Table 1 . The participant mean (± SD) age and BA were 14.6 ± 3.2 and 14.3 ± 3.4 years, respectively. Female participants had more advanced median (Q1-Q3) Tanner stage compared to males (4 [4-5] vs. 2 [1-4], p = 0.004). The two groups had no differences in mean z-scores for height (p = 0.21) and BMI (p = 0.22). Thirty-two (86%) out of 37 participants had Hb H-CS, and 5 participants had Hb H-Paksé. Two male and four female participants had received prednisolone therapy for autoimmune hemolytic anemia. Participants received their first blood transfusion at the age of 4 (1-8) years. Over one year period prior to the study, 31 (84%) participants received blood transfusion every 4-6 weeks, 4 (11%) participants received every 8-12 weeks, and 2 (5%) participants did not receive any. Although female had lower average pre-transfusion Hb than male participants (8.4 ± 0.7 vs. 9.4 ± 1.0 g/dL, p = 0.002), the two groups had no differences in blood transfusion interval (p = 0.59), transfused blood volume (p = 0.46), average serum ferritin (p = 0.98) and liver iron concentrations (p = 0.18). The proportion of participants using iron chelation therapy as well as type of chelators used were not different between genders (p=0.23).