Nontransferrin-bound iron in transfused patients with sickle cell disease

The value of nontransferrin-bound iron (NTBI) as an index of iron overload in patients with thalassemia has been evaluated; however, data in patients with sickle cell disease (SCD) is limited. NTBI levels were evaluated in a cross-sectional study of 43 transfused patients with SCD. Patient charts were reviewed for demographics, status of the spleen, and total number of lifetime transfusions. All patients were chelation naïve and none of the patients had evidence of hepatitis B or C infection. Blood samples were taken for assessment of NTBI and serum ferritin (SF); liver iron concentration (LIC) was determined by R2 magnetic resonance imaging. NTBI levels were generally low with a median of -0.01 μm (range -2.56 to 6.37 μm). Among study variables, NTBI levels were only significantly correlated to age and total number of lifetime transfusions, whereas LIC and SF only significantly correlated with total number of lifetime transfusions. On multivariate analysis, only total number of lifetime transfusions remained independently correlated with NTBI (P = 0.001), SF (P < 0.001), and LIC (P < 0.001). On multivariate stepwise linear regression analysis, SF was a better predictor of LIC than NTBI. In transfused patients with SCD, NTBI levels are low yet correlate significantly with transfusion burden. However, they offer poor predictability of LIC when compared with SF.