COMPARISON BETWEEN TRANSIENT ELASTOGRAPHY AND REAL TIME ELASTOGRAPHY IN EVALUATING LIVER FIBROSIS IN SUBJECTS WITH NON-ALCOHOLIC FATTY LIVER DISEASE

In the last decade several non-invasive methods were proposed
to investigate the degree of liver damage in patients affected by
potentially evolutive chronic liver diseases, both virus-related and
in non-alcoholic fatty liver disease (NAFLD). To date several different
modules are already available; several studies have been
already evaluated the predictive power of the transient elastography
(TE) by FibroScan. In this our study we present the results
of a head to head comparison of TE performed by FibroScan and
Real Time Elastography (RTE) performed by Elaxto, a module integrated
in Esaote MyLab 70 ultrasound (US) machine.
FibroScan utilizes an US transducer probe that transmits vibrations
of mild amplitude and low frequency, inducing elastic shear
wave that propagates through the underlying liver tissue. Pulseecho
ultrasound acquisitions are used to follow the shear wave
propagation and measure its velocity, which is directly related to
tissue stiffness; this is the only method non-integrated into a standard
US system. Not so many studies are available on the different
US machine-integrated methods.
RTE measures probe-induced deformation (strain) of the structures
examined in the B-mode ultrasound image, generating color-
coded maps of the strain distribution, which reflect tissue elasticity.
Instrumental evaluation was integrated by biohumoral analyses,
including complete lipid profile, metabolic status (fasting glucose,
fasting insulin, HOMA index, waist circumference, body mass index),
transaminases (AST, ALT), platelet count, serum albumin,
and AST/ALT ratio, FIB-4 and NAFLD fibrosis score (NFS) calculation.
We included 37 patients (22 men and 15 females), aged between 18
and 63 years old, affected by familial combined hypercholesterolemia
(FCHL) and also presenting criteria for metabolic syndrome
(MetS). FCHL was diagnosed according to LDL-C ≥160 mg/dl
and/or TG ≥200 mg/dl and ApoB ≥120 mg/dl, and familial history
of precocious CVD. MetS was diagnosed according to NCEP-ATPIII
criteria.
FIB-4 was calculated as follows: age(years) * AST levels(U/L) /
platelets(cells/mmc) * ALT levels(U/L); NFS was calculated as
follows: -1.675+0.037 * age (years)+0.094 * BMI (kg/m2)+1.13 *
IFG/diabetes (yes = 1, no = 0)+0.99 * AST/ALT ratio-0.013 * platelet
(×109/l)-0.66 * albumin (g/dl).
We found a significant correlation between liver stiffness assessed
by FibroScan and elastography assessed by RTE (r=0.47;
p<0.001). Moreover, both TE and RTE appeared correlated with
BMI (r=0.51, p<0.001; r=0.38, p<0.005), CRP (r=0.29, p<0.01; r=0.45,
p<0.01), HOMA (r=0.46, p<0.005; r=0.32, P<0.01).
Univariate regression analysis confirmed the association between
RTE and TE (F= 5.346, R2=0.18, p<0.05); however, we found no
association of both TE and RTE with AST/ALT ratio, FIB-4 and
NFS, also due to the limited sample size.
Although these preliminary data are obtained from a small sample
of a larger study of comparison of different non-invasive methods,
they are suggestive for further deepen the power of RTE for the
assessment the degree of damage in liver inflammation and fibrosis
in patients affected by FCHL/MetS If preliminary data will be
reproduced on larger scale, this novel method could be proposed
to reduce the need of liver biopsy to assess the degree of hepatic
inflammation and fibrosis in this subset of patients.