Department of Abdominal Radiology, University of British Columbia, Vancouver General Hospital, Vancouver, BC V5Z 1M9, Canada. firstname.lastname@example.org
ARFI is a new technique that uses acoustic push pulse to generate tissue displacement resulting in shear wave propagation, can be used to measure elasticity of tissue. We aim to assess feasibility of ARFI as a non-invasive method to measure liver fibrosis compared to histological fibrosis scores and to compare our results with the published pooled-meta-analysis cut off values.
MATERIAL AND METHODS:
Prospective study to compare median velocities of ARFI shear wave measurements (Virtual Touch Imaging™ ACUSON S2000, Siemens, Mountain View CA) with Batts and Ludwig liver fibrosis scoring system F0-F4.
70 patients (mean = 49 years) were included. Etiologies were chronic hepatitis C (n = 43), chronic hepatitis B (n = 7) and others (n = 20). Median ARFI values (m/sec) for fibrosis stages and inflammatory stages measured were F0: 1.52, 1.42; F1: 1.50, 1.37; F3: 2.36, 2.41 and F4: 2.61. Areas under the curve for grade 3 = 0.875, stage 3 = 0.867; grade 2 = 0.4, stage 2 = 0.3.Using the cut-off ARFI value of 1.34 m/s for F ≥ 2 suggested in the meta-analysis, we found sensitivity of detecting true F ≥ 2 is 68%, specificity 66%, PPV 74% and NPV 59%. For F ≥ 3 using the cut-off ARFI value of 1.55 m/s, we found sensitivity of 95%, specificity 86%, PPV 74% and NPV 98%. No stage 4 was compared due to insufficient cases.
ARFI has strong correlation with higher fibrosis scores compared to lower. When compared to the pooled meta-analysis cut off values, the sensitivity and specificity for detecting true F ≥ 3 are higher than that of F ≥ 2.