MRI assessment needed for cardiac iron overload in haemoglobinopathies

Unrecognised iron overload is common in patients with myelodysplastic syndromes (MDS), thalassemia major, non-transfusion dependent thalassemia (NTDT) and other chronic anaemias.

Australian research investigated serum ferritin and MRI assessments of liver and myocardial iron in 243 patients at risk of iron overload.

Patients in the Transfusional Iron overload assessed by Magnetic rESonance imaging (TIMES) study were recruited from 13 sites between 2013 and 2015.

The study found myocardial and hepatic siderosis were detected in 10% and 48% of all patients, respectively.

The prevalence of hepatic siderosis was similar in MDS (54.4%), NTDT (50.0%) and other anemia (56.9%), but higher than in thalassemia major (32.9%).

The highest prevalence of myocardial siderosis was observed in thalassemia major (22%).

The study also found a surprisingly high proportion of patients who had received iron chelation therapy still had hepatic siderosis

In over half of all patients with myocardial siderosis, the level of iron overload was severe (mT2∗ <10 ms).

While serum ferritin was found to be an accurate clinical indicator of liver iron overload in most patients, 4.4% of patients had a high liver iron concentration (LIC) and relatively low serum ferritin.

Conversely 7.5% of patients had high serum ferritin that overestimated LIC.

The serum ferritin threshold used to estimate liver iron load was found to be approximately 300 ng/mL higher in myelodysplastic syndrome (MDS) than thalassemia major.

MRI assessment led to a change in chelation therapy in many patient groups – 52% of MDS patients and 59.5% of patients with other anaemia. In chelation-naïve and minimally chelated patients, (re-)starting ICT was the predominant change.

The study also found that low adherence to iron chelation therapy (89.4% reporting medium to low adherence) was a risk factor for both myocardial and hepatic siderosis.

Lead author Professor Joy Ho told the limbic that MRI assessment, which was not MBS-listed, was necessary for the haemoglobinopathy patients who were most in need.

“Most haemoglobinopathy units do it out of their own resources,” she said.

“In our case for instance we have an interested cardiology MRI department who do it on  a research basis. Other hospitals do it out of their own budgets.”

Profesor Ho, from the Royal Prince Alfred Hospital and University of Sydney, said one of the most interesting findings of the study was the high levels of liver iron overload in MDS and “non-haemoglobinopathy” patients, many of whom were not chelated.

“However it was still a leap to argue most people should get MRI because of the expense in scanning so many patients with “non-haemoglobinopathies” who were transfusion dependent. Indeed in the study only 1.4% of MDS patients with serum ferritin <1000 ug/L had elevated LIC, indicating the serum ferritin is a good measure for the majority of patients.”

“… the greatest need is still in the haemoglobinopathy patients. The issue that leads to mortality is cardiac iron overload for haemoglobinopathy patients.”

She added that the suboptimal adherence to chelation was also disturbing.

“Adherence is well known to be the biggest problem of iron control in patients with haemoglobinopathies. In the past it used to be attributed to the fact that the chelation was parenteral. Even with oral chelators the adherence is still not good,” she said.

“I think these adherence figures reflect the approach of patients to chronic illness and highlight for doctors that there is a big problem even with oral chelators.”

She said the effect of iron overload in non-haemoglobinopathy patients was not fully understood.

“The implications of iron on these groups have been adapted from haemoglobinopathy groups so the clinical implications are not fully defined, but there are continuing studies on the impact of iron on the pathogenesis and evolution of these diseases.”

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