PURPOSE
To compare two methods of noninvasive assessment: transient elastography (TE) and acoustic radiation force impulse elastography (ARFI).
PATIENTS AND METHODS
Our study included 114 subjects: 38 healthy volunteers, (considered to have no fibrosis - F 0) and 76 patients with chronic liver disease: 53 who had undergone liver biopsy (LB) (7 with F 1, 24 with F 2, 22 with F 3 Metavir) and 23 previously diagnosed with cirrhosis (F4 Metavir). In each patient we performed a liver stiffness measurement by means of TE and ARFI. ARFI (shear wave velocity quantification) was performed at 3 points: at 0 - 1 cm, at 1 - 2 cm and at 2 - 3 cm under the capsule. For each depth, 5 valid measurements were made, and a median value was calculated, measured in m/sec.
RESULTS
A direct, strong, linear correlation (Spearman rho = 0.848) was found between TE and the stage of fibrosis (p < 0.001). A significant, direct correlation was found between ARFI measurements made 1 - 2 cm and 2 - 3 cm below the liver capsule and the severity of fibrosis (rho = 0.675 and 0.714 respectively). The subcapsularly measured ARFI values showed a poor correlation with fibrosis (rho = 0.469). The best test for predicting significant fibrosis (F ≥ 2) was TE, with the area under receiver-operating characteristic curve (AUROC) 0.908, significantly larger than the AUROCs for ARFI. If only ARFI is considered, measurements made 1 - 2 and 2 - 3 cm below the capsule have the best predictive value, with AUROCs not significantly different from each other (0.767 and 0.731, respectively). For predicting fibrosis (F > 0), TE had the best predictive value: optimized cut-off 5.65 kPa (AUROC -0.898). For ARFI, the cut-offs were: 1.4 m/sec, AUROC -0.747 (1 - 2 cm), and 1.26 m/sec AUROC -0.721 (2 - 3 cm). For predicting cirrhosis (F = 4 Metavir), the optimized cut-offs were: TE -12.9 kPa (AUROC -0.994); ARFI - 1.78 m/sec for measurements made 2 - 3 cm below the capsule, AUROC - 0.951.
CONCLUSION
At present, liver elasticity evaluation by means of ARFI is not superior to TE for the assessment of liver fibrosis. For ARFI, the most reliable results are obtained if measurements are made 1 - 2 and 2 - 3 cm below the liver capsule. ARFI is an accurate test for the diagnosis of cirrhosis.