Qualitative and quantitative magnetic resonance imaging in haemoglobin H disease: Screening for iron overload

OBJECTIVES: To evaluate the clinical utility of magnetic resonance imaging (MRI) in screening for iron overload in non-transfusion dependent Haemoglob in (Hb) H disease. PATIENTS AND METHODS: Thirty-six non-transfusion dependent HbH patients wer e evaluated with axial spin echo T1 and gradient echo T2 MRI of the abdomen and heart, The ratios of signal intensities (SIR) of the liver, spleen, pa ncreas and heart to paraspinous muscles mere calculated. SIR <1 was taken a s indicative of iron overload, Qualitative grading (0-4 scale) of iron over load was also performed. The relationship between T1 and T2 SIR and serum f erritin, and that between qualitative grading and serum ferritin were exami ned using standard statistical methods. Comparisons were also made between qualitative grading and quantitative T1 and T2 SIR data in diagnosing iron overload, Six patients underwent liver biopsies. RESULTS: T2 SIR was more sensitive in detecting iron overload than T1 SLR, Thirty-three Livers, 13 spleens, six pancreas and one heart were diagnosed as having iron overload with T2 SIR, including three patients with normal s erum ferritin, A positive diagnosis by T2 SIR was more closely related to t hat of qualitative grading than T1 SIR. Serum ferritin was negatively corre lated with hepatic SIR (T1 and T2), and with T2 SIR of the spleen and pancr eas, even after adjustment for age. Liver haemosiderosis was confirmed in a ll six patients who underwent liver biopsies. Liver iron concentration of o nly one and a half times the normal was found in one patient with positive MR findings. CONCLUSION: MR is a non-invasive, effective method for early detection of i ron overload particularly in the liver and spleen. Qualitative grading and quantitative T2 SIR data are equivalent in diagnosing iron overload. Routin e screening of non-transfusion dependent HbH patients will identify high ri sk patients in whom early therapeutic intervention may prevent further comp lications and morbidity.