Serum Ferritin a Predictor of Iron Overload in Patients with Thalassemia and Sickle Cell Disease?.

Introduction: Monitoring iron overload by serum ferritin in patients with hemosiderosis is still a routine practice although its limitations are widely studied and well known. Using non-invasive liver iron assessment by quantitative MRI or by biomagnetic liver susceptometry (BLS) with SQUID biomagnetometers would be the better alternative, however, these methods are available at only a few centers worldwide.

Objective: To determine the relationship between serum ferritin (SF) and liver iron concentration (LIC), measured by BLS at CHRCO, in patients with different types of hemosiderosis.

Methods and Patients: A total of 97 patients with thalassemia (TM: 3 to 52 y, 54% females) and 39 patients with sickle cell disease (SCD: 5 to 49 y, 60% female) were prospectively assessed for LIC and SF. Both tests were performed within 2 weeks of each other. Most patients with TM and SCD were chronically transfused, while 10 b-thalassemia intermedia (TI), 5 HbE/β-thalassemia (HbE), and 5 SCD patients were not on transfusion programs. LIC was measured by LT_c SQUID biosusceptometer system (Ferritometer^®, Model 5700, Tristan Technologies, San Diego, USA) under the standardized Hamburg-Torino-Oakland protocol. A non-parametric test (U-test) was utilized to analyze differences between SF and LIC data.

Results: In chronically transfused TM and SCD patients, the median SF and LIC were very similar (Table I). In TI&HbE patients, ferritin results were disproportionately low with respect to LIC. In order to improve prediction of iron stores by SF, the SF/LIC ratio was calculated. There was a significant difference between the median ratios of the two groups of transfused and non- transfused thalassemia patients, 0.82 vs. 0.32 [μg/l]/[μg/g_liver], respectively (p < 0.01). In SCD patients the ratio is significantly (p < 0.01) higher.

Conclusion: Present data confirm ferritin to be a poor predictor of liver iron stores both in sickle cell disease and thalassemia. Relying only on ferritin to monitor iron overload in patients with hemosiderosis can be misleading, especially, in sickle cell disease and non-transfused thalassemia patients. Taking into account disease specific ferritin-LIC relations, could improve the prediction of iron stores. However, assessment of liver iron stores is the ultimate method to initiate and adjust chelation treatment in order to avoid progressive organ injury.

Table I. Median values and ranges ( − ) of serum ferritin (SF) and liver iron concentration (LIC) in transfused (Tx) and non-transfused (non-Tx) hemosiderosis patients.