Transient Elastography (FibroScan®) for Noninvasive Assessment of Liver Amyloidosis.

Liver involvement is frequent in AL amyloidosis patients, and is found in 70% of cases in autopsy series. Histologic diagnosis of amyloid deposition is mandatory, preferably by biopsies of non-hepatic tissue, liver biopsy being associated with an increased risk of bleeding. FibroScan, a non invasive method for measuring liver stiffness, is used to measure liver fibrosis in patients with viral hepatitis. We postulated that amyloid liver deposition in AL could enhance liver stiffness and that may help for the diagnosis of liver amyloidosis.

41 consecutive AL patients with systemic disease seen at the French Reference Center for AL amyloidosis were analyzed: 17 had liver AL, 23 cardiac AL, and 13 no liver or cardiac involvement according to the criteria defined by the Tours Consensus Opinion on Amyloidosis (2005). All had liver stiffness measured by FibroScan simultaneously with 76 controls: 16 healthy controls, 10 multiple myeloma and 50 consecutive patients chronically infected with hepatitis C virus (HCV). According to the manufacturer's criteria, liver stiffness was interpretable in 32 (78%) of AL patients and in 68 (89%) of the control group. The Mann Whitney test with Bonferroni correction for multiple comparisons was used to compare the interpretable liver stiffness values between the groups.

The liver stiffness was not statistically different between the healthy (median 4,6 range 2,8-6,5 KPa) and the myeloma controls (median 5,4 range 3,3-11,9 KPa) and both were considered as the negative control group. The negative control group had a liver stiffness significantly different from the HCV group (median 6,8 range 2,9-69,1 KPa, p<0.001), but not from the AL group without liver or cardiac involvement (median 6,1 range 4,2-17,5 KPa, p=0,25). The liver stiffness of AL patients with liver (with or without cardiac) involvement, was significantly higher (median 27,4 range 10,3-75 KPa) than the one of the negative control group (p<0.001), or the HCV group (p=0.001), and the AL group without liver or cardiac involvement (p=0.001). The relationship between AL liver involvement and the liver stiffness value was tested using ROC curve analysis with an optimal cut-off value of 9,8 KPa, a sensitivity of 100% (95%CI71,5 - 100,0), a specificity of 75.6% (95%CI64,6 - 84,7) and a ROC AUC of 0.92 (p=0.0001). In order to favour specificity for the diagnosis of AL liver involvement in non specific clinical situations, we chose the cut-off value of 17.5 KPa (specificity 94,87% (95%CI87,4 - 98,6), sensitivity 63,64% (95%CI30,8 - 89,1).

FibroScan is a useful non invasive tool which may suggest that a patient with undefined signs (enlarged liver, asymptomatic cholestasis, isolated monoclonal gammopathy) has liver amyloidosis and may help to define liver involvement in patients with proven amyloidosis, especially when liver stiffness reaches the cut-off value of 17,5 KPa.

No relevant conflicts of interest to declare.