Abstract

The treatment of sickle cell disease (SCD) is mainly supportive, except for a minority, who receive bone marrow transplantation (BMT). Serum ferritin (SF) is routinely available but is notoriously unreliable as a tool for iron-overload assessment since it is an acute-phase reactant. Although blood transfusion is one of the most effective ways to deal with specific acute and chronic complications of SCD, this strategy is often associated with alloimmunization, iron overload, and hemolytic reactions. This study, thus, aims to evaluate iron overload in patients with SCD on chronic blood transfusions and specifically, correlate SF with the current standard of care of iron-overload assessment using MRI-based imaging techniques. Amongst a historic cohort of 58 chronically transfused patients with SCD, we were able to evaluate 44 patients who are currently alive and had multiple follow-up testing. Their mean age (±SD) was 35 (9) years and comprised of 68.2% of women. The studied iron-overload parameters included cardiac T2* MRI, liver iron concentration (LIC) by Liver T2* MRI, and serial SF levels. Additionally, in a smaller cohort, we also studied LIC by FerriScan© R2-MRI. Chronic blood transfusions were necessary for severe vaso-occlusive crisis (VOC) (38.6%), severe symptomatic anemia (38.6%), past history of stroke (15.9%), and recurrent acute chest syndrome (6.9%). About 14 (24%) patients among the original cohort died following SCD-related complications. Among the patients currently receiving chelation, 26 (96%) are on Deferasirox (DFX) [Jadenu® (24) or Exjade® (2)], with good compliance and tolerance. However, one patient is still receiving IV deferoxamine (DFO), in view of the significantly high systemic iron burden. In this evaluable cohort of 44 patients, the mean SF (±SD) reduced marginally from 4,311 to 4,230 ng/ml, mean Liver T2* MRI dropped from 12 to 10.3 mg/gm dry weight, while the mean cardiac T2*MRI improved from 36.8 to 39.5 ms. There was a mild to moderate correlation between the baseline and final values of SF ng/ml, r = 0.33, p = 0.01; Cardiac T2* MRI ms, r = 0.3, p = 0.02 and Liver T2* MRI mg/kg dry weight, r = 0.6, p < 0.001. Overall, there was a positive correlation between SF and Liver T2* MRI (Pearson's r = 0.78, p < 0.001). Cardiac T2*MRI increased with the decreasing SF concentration, showing a negative correlation which was statistically significant (Pearson's r = −0.6, p < 0.001). Furthermore, there was an excellent correlation between SF ng/ml and LIC by FerriScan© R2-MRI mg/g or mmol/kg (Spearmen's rho = −0.723, p < 0.008) in a small subset of patients (n = 14) who underwent the procedure. In conclusion, our study demonstrated a good correlation between serial SF and LIC by either Liver MRI T2* or by FerriScan© R2-MRI, even though SF is an acute-phase reactant. It also confirms the cardiac sparing effect in patients with SCD, even with the significant transfusion-related iron burden. About 14 (24%) patients of the original cohort died over the past 15 years, indicative of a negative impact of iron overload on disease morbidity and mortality.

Highlights

  • Sickle cell disease (SCD) refers to a group of inherited conditions, characterized by sickle-shaped red blood cells that precipitate recurrent episodes of vaso-occlusive episodes (VOC)

  • Chronic blood transfusions were indicated for severe vaso-occlusive crisis (VOC) in 24 (41.4%), severe symptomatic anemia in 19 (32.8%), history of stroke in nine (15.5%), and recurrent acute chest syndrome in six (10.3%) patients

  • In 2006, the WHO recognized hemoglobinopathies, including sickle cell disease (SCD), as a global public health problem and Oman has a high prevalence of hemoglobin (Hb) disorders [3]

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Summary

Introduction

Sickle cell disease (SCD) refers to a group of inherited conditions, characterized by sickle-shaped red blood cells that precipitate recurrent episodes of vaso-occlusive episodes (VOC). It is estimated that 312,000 people with sickle hemoglobin (Hb) are born each year throughout the world, with the majority of these births (236,000) in sub-Saharan Africa [1], whilst, in Oman, the sickle cell gene has an overall prevalence of 6% [2]. During VOC, the vessel lumen is blocked by cells interrupting the capillary blood flow to various organs and other parts of the body. This precipitates an inflammatory process that leads to painful crises and damage to the brain, the liver, the kidneys, the lungs, the spleen, and other vital organs [15, 16]. Painful crises affect virtually all patients with SCD, often beginning in late infancy and recurring throughout life [17, 18]

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