Using SQUID biomagnetic liver susceptometry in the treatment of thalassemia and other iron loading diseases

Abstract

In iron overload diseases in humans, the liver isthe main place of iron storage accounting for atleast 70–90% of the excessive iron burden. SQUIDbiomagnetic liver susceptometry (BLS) has be-come a routine method in monitoring iron over-load in post-transfusions siderosis, iron loadinganemias, or hereditary haemochromatosis. In thelast decade, we have measured the liver iron con-centration (LIC) in patients with b-thalassemiamajor –n ‹722ƒ, b-thalassemia intermedia–n ‹40ƒ, sickle cell/b-thalassemia –n ‹20ƒ, b-thalassemia minor –n ‹11ƒ, ex-thalassemia afterbone marrow transplantation –n ‹26ƒ, sickle celldisease –n ‹11ƒ, aplastic anemia –n ‹10ƒ, Dia-mond Blackfan syndrome –n ‹6ƒ, and ex-leuke-mic patients after bone marrow or stem celltransplantation –n ‹76ƒ. LIC was also measuredin 661 subjects suspected for hereditary haemo-chromatosis. In 141/149 subjects (94.6%) withLIC >1000 lg/g, a homozygous C282Y-mutationwas found, indicating the typical genetic haemo-chromatosis in Northern Europe.As shown in Table 1, our data confirm thatserum ferritin (SF) is only a poor predictor of ironoverload [1,2]. Some European centers for b-tha-lassemia major for example, in Italy, Greece,Switzerland and Germany are using the SQUID–BLS method now as part of their regular follow-upprogramme [2,3]. The Hamburg biosusceptometerfacility can handle at maximum 16 patients perday. On-line data analysis is correcting for indi-vidual variability of the magnetic signature ofbody tissue by empirical estimation of the mag-netic thorax susceptibility from body mass index.These results deviate from the more precise o•-lineanalysis results (not available at run-time) by lessthan 10%. BLS is extremely useful in thalassemiapatients: (i) with relatively high SF under regularchelator treatment, especially in children, in orderto avoid side-e•ects from overdosage, (ii) with lowSF, but good compliance with chelating treatment,in order to exclude severe siderosis, (iii) in youngpatients (3–10 yr), in order to adjust the individ-ually optimum chelator dose, (iv) in patients withbad chelator compliance, in order to achieve ahigher motivation when confronting these patientswith the BLS results directly, (v) in patients with b-thalassemia intermedia having relatively lower SFvalues, in order to define the onset of chelationtreatment.The suitability of the BLS method for deter-mining the long-term e†cacy of iron chelationtherapy has been demonstrated in studies with theoral chelator deferiprone in more than 200 patients