Non‐transferrin bound labile plasma iron and iron overload in Sickle Cell Disease: a comparative study between Sickle Cell Disease and β thalassemic patients

Background: Blood transfusions are the standard of care in β thalassemia and transfusions are also indicated in sickle cell disease (SCD) patients with hypersplenism, recurrent vaso‐occlusive crises and for stroke prevention. Iron overload caused by blood transfusions in thalassemia and in SCD may affect morbidity and mortality. Recent studies of iron overload in SCD suggest that the biologic features of SCD and the chronic inflammatory state may protect SCD patients from iron damage. Designs and methods: In view of the controversy regarding the effect of iron overload in patients with SCD we studied the iron status, including non‐transferrin bound iron (NTBI) and labile plasma iron (LPI) levels in a cohort of 36 SCD patients and compare the results with 43 thalassemia patients. Results: Our results indicate that none of the SCD patients had clinical symptoms of iron overload. Only two SCD patients had NTBI values in the gray zone (0.4 units) and none had positive values. By contrast, 14 patients with thalassemia major and three with thalassemia intermedia had NTBI values above 0.6, level that are in the positive pathological range. Similarly, four thalassemia patients, but only one SCD patient had positive LPI levels. Conclusions: The parameters of iron status in SCD patients, even after frequent transfusions are different when compared to patients with thalassemia. The low NTBI and LPI levels found in patients with SCD are in keeping with the absence of clinical signs of iron overload in this disease.     

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.     

Non‐transferrin‐bound iron in haematological patients during chemotherapy and conditioning for autologous stem cell transplantation

Free iron induced hydroxyl radical formation is one possible mechanism for tissue injury during cytotoxic therapy. We studied the appearance of free, non‐transferrin‐bound iron (NTBI) at baseline and during the 20‐d period after the onset of cytotoxic chemotherapy in patients with haematological malignancy undergoing intensive chemotherapy or conditioning for autologous stem cell transplantation (aSCT). NTBI was detected on average for 15.6 d in patients treated with chemotherapy only, and for 6.1 d in patients undergoing aSCT. The recovery of the bone marrow function coincided with the disappearance of NTBI. The type of the conditioning regimen was also associated with the appearance of NTBI. The timing of the presence of NTBI accords with the presence of the most important non‐infectious complication of intensive chemotherapy and autologous transplantation, mucosal injury, and free iron is likely to contribute to this and probably other complications of the intensive treatments.     

Organ iron accumulation in chronically transfused children with sickle cell anaemia: baseline results from the TWiTCH trial

Transcranial Doppler (TCD) With Transfusions Changing to Hydroxyurea (TWiTCH) trial is a randomized, open‐label comparison of hydroxycarbamide (also termed hydroxyurea) versus continued chronic transfusion therapy for primary stroke prevention in patients with sickle cell anaemia (SCA) and abnormal TCD. Severity and location of iron overload is an important secondary outcome measure. We report the baseline findings of abdominal organ iron burden in 121 participants. At enrollment, patients were young (9·8 ± 2·9 years), predominantly female (60:40), and previously treated with transfusions (4·1 ± 2·4 years) and iron chelation (3·1 ± 2·1 years). Liver iron concentration (LIC; 9·0 ± 6·6 mg/g dry weight) and serum ferritin were moderately elevated (2696 ± 1678 μg/l), but transferrin was incompletely saturated (47·2 ± 23·6%). Spleen R2* was 509 ± 399 Hz (splenic iron ~13·9 mg/g) and correlated with LIC (r² = 0·14, P = 0·0008). Pancreas R2* was increased in 38·3% of patients but not to levels associated with endocrine toxicity. Kidney R2* was increased in 80·7% of patients; renal iron correlated with markers of intravascular haemolysis and was elevated in patients with increased urine albumin‐creatinine ratios. Extra‐hepatic iron deposition is common among children with SCA who receive chronic transfusions, and could potentiate oxidative stress caused by reperfusion injury and decellularized haemoglobin.     

Iron overload across the spectrum of non‐transfusion‐dependent thalassaemias: role of erythropoiesis,splenectomy and transfusions

Non‐transfusion‐dependent thalassaemias (NTDT ) encompass a spectrum of anaemias rarely requiring blood transfusions. Increased iron absorption, driven by hepcidin suppression secondary to erythron expansion, initially causes intrahepatic iron overload. We examined iron metabolism biomarkers in 166 NTDT patients with β thalassaemia intermedia (n  = 95), haemoglobin (Hb) E/β thalassaemia (n  = 49) and Hb H syndromes (n  = 22). Liver iron concentration (LIC ), serum ferritin (SF ), transferrin saturation (TfSat) and non‐transferrin‐bound iron (NTBI ) were elevated and correlated across diagnostic subgroups. NTBI correlated with soluble transferrin receptor (sTfR ), labile plasma iron (LPI ) and nucleated red blood cells (NRBC s), with elevations generally confined to previously transfused patients. Splenectomised patients had higher NTBI , TfSat, NRBC s and SF relative to LIC , than non‐splenectomised patients. LPI elevations were confined to patients with saturated transferrin. Erythron expansion biomarkers (sTfR , growth differentiation factor‐15, NRBC s) correlated with each other and with iron overload biomarkers, particularly in Hb H patients. Plasma hepcidin was similar across subgroups, increased with >20 prior transfusions, and correlated inversely with TfSat, NTBI , LPI and NRBC s. Hepcidin/SF ratios were low, consistent with hepcidin suppression relative to iron overload. Increased NTBI and, by implication, risk of extra‐hepatic iron distribution are more likely in previously transfused, splenectomised and iron‐overloaded NTDT patients with TfSat >70%.     

Mass spectrometry evaluation of the hepcidin‐25 assay in the differential diagnosis of iron deficiency anaemia with concurrent inflammation and anaemia of inflammation in elderly patients

In this study, mass spectrometry was used to evaluate the hepcidin‐25 assay in the differential diagnosis of iron deficiency anaemia with concurrent inflammation and anaemia of inflammation in elderly patients using the absence of stainable bone marrow iron as the gold standard criterion for iron deficiency (ID). In addition, correlation coefficients for hepcidin‐25 vs. haematimetric and biochemical iron parameters, and C‐reactive protein (CRP) were determined. The optimal cut‐off for hepcidin‐25 was 31.5 ng/mL corresponding to a sensitivity and specificity of 82% and 95%, respectively, for ID. For ferritin, a sensitivity and specificity of 70% and 100%, respectively, correspond to an optimal cut‐off of 41.5 μg/L. Receiver operating characteristics curve analysis revealed that mass spectrometry analysis of hepcidin‐25 does not appear to be superior to ferritin in the diagnosis of ID in elderly anaemic patients with concurrent inflammation. Hepcidin‐25 shows a strong positive correlation with ferritin, and also correlates positively with CRP, in this patient population.     

Defining serum ferritin thresholds to predict clinically relevant liver iron concentrations for guiding deferasirox therapy when MRI is unavailable in patients with non‐transfusion‐dependent thalassaemia

Liver iron concentration (LIC) assessment by magnetic resonance imaging (MRI) remains the gold standard to diagnose iron overload and guide iron chelation therapy in patients with non‐transfusion‐dependent thalassaemia (NTDT). However, limited access to MRI technology and expertise worldwide makes it practical to also use serum ferritin assessments. The THALASSA (assessment of Exjade^® in non‐transfusion‐dependent THALASSemiA patients) study assessed the efficacy and safety of deferasirox in iron‐overloaded NTDT patients and provided a large data set to allow exploration of the relationship between LIC and serum ferritin. Using data from screened patients and those treated with deferasirox for up to 2 years, we identified clinically relevant serum ferritin thresholds (for when MRI is unavailable) for the initiation of chelation therapy (>800 μg/l), as well as thresholds to guide chelator dose interruption (<300 μg/l) and dose escalation (>2000 μg/l). (clinicaltrials.gov identifier: NCT00873041).     

Systematic review and meta‐analysis to determine the impact of iron depletion in dysmetabolic iron overload syndrome and non‐alcoholic fatty liver disease

Aims

Iron reduction has been proposed as treatment for dysmetabolic iron overload syndrome (DIOS) and non‐alcoholic fatty liver disease (NAFLD), but results of published trials are conflicting. We undertook a systematic review and meta‐analysis to determine the impact of phlebotomy in DIOS and NAFLD.

Methods

We searched multiple databases systematically for studies evaluating the impact of phlebotomy in DIOS and NAFLD. We calculated weighted summary estimates using the inverse variance method. Study quality was assessed using the Cochrane collaboration tool.

Results

We identified nine studies with 820 patients (427 had phlebotomy, 393 lifestyle changes alone). Iron depletion did not improve the Homeostasis Model Assessment (HOMA) index (mean difference [MD] ?0.6; confidence interval (CI), ?1.7, 0.5; P = 0.3), insulin level (MD ?0.8 mU/L; CI, ?5.3, 3.7; P = 0.73), or aspartate aminotransferase (AST) (MD ?0.7 IU/L; CI, ?3.2, 1.8; P = 0.6) in DIOS and/or NAFLD patients as compared to lifestyle changes alone (five studies, 626 patients). There was mild improvement in alanine aminotransferase (ALT) (MD ?6.6 IU/L; CI, ?11, ?2.1); P < 0.01), but the effect size was very small (Cohen's d, 0.15; r statistic, 0.07). Even in the subgroup of patients with NAFLD and hyperferritinemia, phlebotomy did not improve the HOMA index, insulin level, ALT, or AST. Additionally, no study showed significant improvement in liver inflammation or fibrosis with iron reduction.

Conclusions

Phlebotomy does not bring about significant improvement in indices of insulin resistance, liver enzymes, or liver histology in patients with DIOS and/or NAFLD compared to lifestyle changes alone. Current evidence does not support the use of phlebotomy in patients with DIOS or NAFLD.

     

The impact of liver steatosis on the ability of serum ferritin levels to be predictive of liver iron concentration in non‐transfusion‐dependent thalassaemia patients

This study analysed the impact of liver steatosis (LS) on the parameters of iron overload in 110 patients with non‐transfusion dependent thalassaemia (NTDT). LS was diagnosed by ultrasound. Liver iron concentration (LIC) measurements were available for 64 patients who underwent a magnetic resonance imaging (MRI) scan. LS was frequent (35·5%) and was significantly more prevalent in males than in females (49·0% vs. 24·6%, P = 0·008). Patients with LS had significant higher levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), ALT/AST ratio and ferritin than those without, but LIC values were comparable. An ALT/AST ratio >0·89 predicted the presence of LS with a sensitivity of 0·872 and a specificity of 0·901 (P < 0·0001). Ferritin levels correlated with LIC values (R = 0·558, P < 0·0001) but the correlation was stronger in patients without LS (R = 0·656, P < 0·0001) than in patients with LS (R = 0·426, P = 0·05). LS is a frequent issue in NTDT patients and should be suspected in the presence of an ALT/AST ratio >0·89. Recently, serum ferritin thresholds that predict clinically relevant LIC for guiding iron chelation therapy when MRI is unavailable have been determined. Our data show that LS may cause increase in ferritin levels and may be responsible for anticipating/exceeding chelation treatment in NTDT patients in the absence of LIC evaluation.     

Assessing cardiac and liver iron overload in chronically transfused patients with sickle cell disease

Transfusional iron overload represents a substantial challenge in the management of patients with sickle cell disease (SCD) who receive chronic or episodic red blood cell transfusions. Iron‐induced cardiomyopathy is a leading cause of death in other chronically transfused populations but rarely seen in SCD. Study objectives were to: (i) examine the extent of myocardial and hepatic siderosis using magnetic resonance imaging (MRI) in chronically transfused SCD patients, and (ii) evaluate the relationship between long‐term (over the 5 years prior to enrolment) mean serum ferritin (MSF), spot‐ferritin values and liver iron content (LIC) measured using MRI and liver biopsy. Thirty‐two SCD patients (median age 15 years) with transfusional iron overload were recruited from two U.S. institutions. Long‐term MSF and spot‐ferritin values significantly correlated with LIC by MRI‐R2* (r = 0·77, P < 0·001; r = 0·82, P < 0·001, respectively). LIC by MRI‐R2* had strong positive correlation with LIC by liver biopsy (r = 0·98, P < 0·001) but modest inverse correlation with cardiac MRI‐T2* (r = ?0·41, P = 0·02). Moderate to severe transfusional iron overload in SCD was not associated with aberrations in other measures of cardiac function based on echocardiogram or serum biomarkers. Our results suggest that SCD patients receiving chronic transfusions may not demonstrate significant cardiac iron loading irrespective of ferritin trends, LIC and erythropoiesis suppression.     

No evidence for myocardial iron overload and free iron species in multitransfused patients with sickle/β0‐thalassaemia

Iron overload (IO) in the heart is a life‐threatening complication in transfusion‐dependent patients with thalassaemia major (TM) and to a lesser extent in sickle cell disease (SCD), while no data are available in patients with sickle/β⁰‐thalassaemia. Iron deposition in the heart, liver and pancreas was assessed using T2* MRI sequences, as well as free iron species assays – non‐transferrin bound iron (NTBI) and labile plasma iron (LPI), in addition to serum ferritin, percentage transferrin saturation and serum hepcidin, in 10 multitransfused patients (>30 yr) with sickle/β⁰‐thalassaemia. None of the patients had iron deposition in the heart. Three patients had mild, one had moderate, and two had severe liver IO. Two patients had mild iron deposition in the pancreas. In all the patients, serum hepcidin levels were normal – NTBI and LPI were not detected. Possible explanations of these findings are discussed.     

Magnetic resonance imaging in the evaluation of iron overload in patients with beta thalassaemia and sickle cell disease

Magnetic resonance imaging (MRI) appears to be useful for monitoring iron overload in thalassaemia. We studied 106 patients with beta-thalassaemia: 80 with thalassaemia major (TM) and 26 with thalassaemia intermedia (TI). Thirty-five patients with sickle cell disease (SCD) were also evaluated. Serum ferritin, liver and myocardial T2-relaxation time and liver iron concentration (LIC) were measured. LIC values, based on biopsies from 29 patients, showed a close inverse correlation with the respective liver T2-values, along with a strong positive correlation with ferritin levels in all patients. Heart T2-values correlated with left ventricular ejection fraction in TM and SCD, but not in TI patients. Both liver and heart T2-values were significantly lower in TM patients than those of TI, and SCD patients. Ferritin levels showed a strong correlation with liver T2-values in all three groups of patients. Similarly, a negative correlation was found between serum ferritin levels and heart T2-values in TM, but not in TI and SCD patients. Heart and liver T2-values showed a significant correlation only in TM patients. These results suggest that the MRI technique (T2 relaxation time) used in our study, is a reliable, safe and non-invasive method for the assessment of the deposition of iron in the liver; results for the heart become reliable only when there is heavy iron deposition.     

Expression of cell-surface transferrin receptor following in vitro stimulation of peripheral blood lymphocytes in patients with beta-thalassaemia and iron-deficiency anaemia

The ferritin concentration in peripheral blood lymphocyte extracts was measured in 10 normal subjects, 7 patients with homozygous beta-thalassaemia, and 5 patients with iron-deficiency anaemia. The mean intracellular ferritin content was found increased in beta-thalassaemia and reduced in iron-deficient patients. Incubation of mononuclear cells in phytohaemagglutinin medium led to an increase of DNA synthesis concomitant with an increased number of lymphocytes bearing transferrin receptor and interleukin-2 receptor as measured by immunofluorescent technique. Although there was an immunological impairment of lymphocytes in patients with either iron depletion or iron loading compared to normal subjects, their ability to express transferrin receptor and interleukin-2 receptor on their cell surface was normal.