**2. Liver biopsy – An imperfect gold standard**

Liver biopsy was performed by P Ehrlich in 1883 and became a common exploration meth‐ od in 1958, when G Menghini introduced the first biopsy technique with a needle that was named after him [1].

Because of the limitations and invasive nature of liver biopsy, other non-invasive means are being tested for the evaluation of diffuse hepatopathies, and implicitly of fibrosis and steato‐ sis as major prognosis factors in the evolution of the hepatopathy. Therefore, there is interest in developing other methods, either serological or imaging, which are all non-invasive, in order to determine the presence and degree of fibrosis, as well as of steatosis. One of these

Non-Invasive Evaluation of Liver Steatosis, Fibrosis and Cirrhosis in Hepatitis C Virus Infected Patients Using

Unidimensional Transient Elastography (Fibroscan®)

http://dx.doi.org/10.5772/52621

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The divice consists of a special transducer, that is placed in the axis of a mechanical vibrator. The vibrator generates pain-free vibrations that produce a train of elastic waves that will be transmited through the skin and subcutaneous tissue to the liver. At the same time with acti‐ vating the vibration, the probe performs a number of ultrasound acquisitions (the same process of emision-reception used in conventional ultrasonography), with a frequency of 4 kHz. Reports on the tissues deformation caused by elastic wave transmission can be formu‐ lated by comparing the succesive ultrasound (US) signals acquired in this manner. The time necessary for the train of waves to propagate along the area of interest, as well as propaga‐ tion velocities are being measured. This way liver stiffness can be determined using the fol‐ lowing formula: E = 3ρVs<sup>2</sup> (E – elasticity module, ρ – density, a constant of the material; Vs – propagation velocity within the liver parenchyma). The more rigid the material, the higher

During the examination, the patient is lying down, face-up, with his right arm placed in hy‐ perextension and above the head for an adequate exposure of his right hypocondrium. The probe is placed in contact with the patient's skin, at the level of an intercostal space, in an

When the button on the probe is pushed, the vibration that will be transmitted through the liver is activated. By analyzing tissue deformation report, the software of the equipment will measure the liver stiffness (LS). The results are given in kiloPascals (kPa) and correspond to a median value of 10 valid measurements. The machine can determine values between 2.5

The monitor of the machine will display data regarding the patient's identity, diagnosis, name of the examining physician, the instantaneous value of liver stiffness (CS), the median stiffness resulted from 10 valid measurements, the success rate (SR), as well as the variation

To be in agreement with the recommendations of the producer, the success rate must be at least 60% and IQR must not exceed 30% of the median liver stiffness [16], even though it seems that the best concordance with liver biopsy is obtained when this value does not ex‐

There are no studies that especially focus on the issue of the variability of LS measurements and therefore the interpretation of the results is done according to the experience of the ex‐

methods is unidimensional transient elastography (Fibroscan).

the velocity of propagation [15-17].

and 75 kPa.

ceed 20% of the median [18].

area of full liver dullness and avoiding any large vessels.

of the 10 values compared with the median value (IQR).

**3. The principle of unidimentional transient elastography**

*Liver biopsy provides a lot of information* [2-6]:


At the same time, one can not ignore the fact that liver biopsy has significant limitations: possible complications, including mortality; important sampling errors; high cost; subjective appreciations that may be due to important intra and interobserver variations.

Biopsy complications may vary in magnitude and frequency depending on the subjacent liv‐ er pathology. Among these can be listed: pain (epigastric area, right shoulder, right hypo‐ condrium); vagal response; hemorrhagic accidents (hemoperitoneum, hemobilia, liver hematoma); bile peritonitis, bilioma; bacteremia; infections and abscesses; pneumothorax and/or pleural reactions; hemothorax; arteriovenous fistula; subcutaneous emphysema; ad‐ verse reactions caused by the anesthetic; breaking of the biopsy needle; penetration of other organs: lung, kidney, colon. The mortality associated with this technique is low, but it is possible in 0.0088-0.3% of the cases [7-11].

The most significant problem encountered when interpreting a biopsy is represented by samplig error. Considering the fact that the tissue sample obtained through liver biopsy rep‐ resents approximately 1/50.000-1/100.000 of the liver volume, it can be inadequate for the di‐ agnosis of diffuse liver conditions, as the histopathological changes may be spread unevenly [5]. Even though liver biopsy is considered the standard exploration in the evaluation of liv‐ er diseases, it has an accuracy of only 80% in staging fibrosis and it can miss cirrhosis in 30% of the cases [12]. For example, Ragev reported that in HCV patients, there is a discrepancy of at least 1 stage between the right and left lobe in 33% of the patients [13]. At the same time, Siddique observed that a difference of at least one stage between 2 samples (15 mm long) cut from the same area occurs in 45% of the cases [14].

Considering all these observations, the results of the studies performed to validate a noninvasive diagnosis method must be interpreted with caution, since they are compared with an imperfect "gold standard".

Because of the limitations and invasive nature of liver biopsy, other non-invasive means are being tested for the evaluation of diffuse hepatopathies, and implicitly of fibrosis and steato‐ sis as major prognosis factors in the evolution of the hepatopathy. Therefore, there is interest in developing other methods, either serological or imaging, which are all non-invasive, in order to determine the presence and degree of fibrosis, as well as of steatosis. One of these methods is unidimensional transient elastography (Fibroscan).
