Utility of Transient Elastography (Fibroscan) in Estimating Hepatic Iron Concentration in Comparison to MRI in Patients with Transfusion Dependent Hemoglobinopathies

Background

Patients with severe hereditary anemias (e.g. β-Thalassemia Major) are transfusion-dependent for survival. Current guidelines suggest monitoring serum ferritin every three months and annual MRI to assess hepatic and cardiac iron load¹. However, MRI, particularly the R2 sequence (FerriScan) which has high specificity and sensitivity in estimating the liver iron concentration, is expensive and not always readily available. Transient elastography (FibroScan) measures liver's stiffness and predicts fibrosis. Previous studies have suggested its utility in other conditions that increase liver stiffness, such as amyloidosis²and perhaps iron overload.

Aim

To determine if FibroScan value correlates with hepatic iron concentration estimated using R2 MRI (FerriScan), and/or serum ferritin level.

Methods

A prospective cross-sectional study was conducted at a university-affiliated tertiary care center (St. Paul’s Hospital, Vancouver, BC) in 2013 and 2014. Inclusion criteria: Age ≥ 19 years with transfusion-dependent hereditary anemias. Exclusion criteria: liver cirrhosis, primary liver disease (e.g. Wilson’s disease, hereditary hemochromatosis), and chronic viral hepatitis (e.g. Hepatitis B, C and HIV). In addition to having annual MRI and ferritin levels monitored every three months, subjects underwent FibroScan within six months of MRI in 2013. In 2014, participants were invited to undergo repeat FibroScan within three months of the annual MRI. Linear regression analysis was used to determine if there is any correlation/linear fit between FibroScan result, MRI result, and ferritin levels. This study was approved by the University of British Columbia Research Ethics Board.

Results

20 subjects have been recruited as of August 1, 2014, with 35 and 33 complete FibroScan and MRI results, respectively. 14 (70%) were female. Mean age was 30.7±9.8 years. Most common primary diagnosis was transfusion-dependent beta-thalassemia (Major and intermedia) (n=17).

Linear regression analysis showed a weakly positive correlation between hepatic iron concentrations estimated with R2 MRI (FerriScan) and ferritin levels (R²=0.29; p=0.004), when they are performed within four weeks apart. The correlation remained statistically significant when all subjects were included regardless of time lapse between the two investigations (R²=0.30; p=0.001). However, FibroScan values did not appear to correlate with MRI, regardless of whether the scans are performed within six months (R²=0.011; p=0.58) or three months apart (R²=0.035; p=0.44). Similarly, there was no correlation between FibroScan and Ferritin (R²=0.022; p=0.49) when the investigations were performed within 4 weeks part.

Conclusion

Interim analysis did not demonstrate any correlation between FibroScan result and MRI-estimated hepatic iron concentration. A final analysis will be performed upon complete formal evaluation of the remaining MRI and FibroScan data.

References

1. Remacha A, Sanz C, Contreras E, et al. Guidelines on haemovigilance of post-transfusional iron overload. Blood Transfus. 2013; 11(1): 128-139

2. Loustaud-Ratti V, Cypierre A, Rousseau A, et al. Non-invasive detection of hepatic amyloidosis: Fibroscan, a new tool. Amyloid 2013; 18(1): 19-24