**7. Tests of fibrosis**

#### **7.1. Noninvasive laboratory tests**

Noninvasive tests of hepatic fibrosis are used for the staging of fibrosis in patients with chronic liver disease. The tests are often used to differentiate patients with significant fibrosis (F2 to F4) from those with minimal or no fibrosis (F0 to F1). There are four commercial serum marker systems that have been validated: FibroTest/FibroSure (marketed in the United States by LabCorp), Hepascore (Quest Diagnostics), FibroSpect (Prometheus Corp), and the European Liver Fibrosis Study Group panel (not available in the United States). In addition, the aspartate aminotransferase-to-platelet ratio (APRI) has also been studied. The APRI has the advantage of being easily calculated using data available from routine laboratory tests.

All the serum tests have limitations: (a) they typically reflect the rate of matrix turnover, not deposition, and thus tend to be more elevated when there is high inflammatory activity. By contrast, extensive matrix deposition can go undetected if there is minimal inflammation. (b) None of the markers are liver specific, and concurrent sites of inflammation may contribute to serum levels. (c) Serum levels are affected by clearance rates, which may be impaired due to either sinusoidal endothelial cell dysfunction or impaired biliary excretion. (d) They are surrogates, not biomarkers [40].

#### **7.2. Elastogram (Fibroscan)**

Elevated blood levels of liver enzymes ALT and AST occur when the membrane of the liver cells is damaged and liver enzymes leak into the blood stream, thus indicating ongoing liver injury. The degree of elevation of liver enzymes present in the blood correlates with the severity of liver cell injury. However, blood levels of liver enzymes do not correlate with the degree or severity of hepatic fibrosis. The important tests that reflect liver synthetic function are serum bilirubin, albumin, and international normalized ratio (INR). Abnor‐ mal serum albumin, bilirubin, or prothrombin time may be seen in the setting of im‐ paired hepatic synthetic function. Some models used to evaluate liver disease severity are helpful for the assessment of liver function, for example, the model for end-stage liver disease (MELD). The MELD score was adopted by UNOS in 2002 for use in deceased donor liver allocation for adults with cirrhosis. MELD is a prospectively developed and validat‐ ed chronic liver disease severity scoring system that uses a patient's laboratory values for serum bilirubin, serum creatinine, and INR to predict a 3-month survival [36]. The MELD equation that is currently used by UNOS for prioritizing allocation of deceased donor livers for transplantation is as follows: MELD = 3.8\*loge(serum bilirubin [mg/dL]) + 11.2\*loge(INR) + 9.6\*loge(serum creatinine [mg/dL]) + 6.4. Patients with the combination of serum creati‐ nine ≤1 mg/dl, serum bilirubin ≤1 mg/dl, and INR ≤1 will receive the minimum score of 6 MELD points. In addition, UNOS has set an upper limit for the MELD score at 40 points. However, there is no need to go through the above time-consuming equation because

several online tools are available for calculating the MELD score [37-39].

of being easily calculated using data available from routine laboratory tests.

Noninvasive tests of hepatic fibrosis are used for the staging of fibrosis in patients with chronic liver disease. The tests are often used to differentiate patients with significant fibrosis (F2 to F4) from those with minimal or no fibrosis (F0 to F1). There are four commercial serum marker systems that have been validated: FibroTest/FibroSure (marketed in the United States by LabCorp), Hepascore (Quest Diagnostics), FibroSpect (Prometheus Corp), and the European Liver Fibrosis Study Group panel (not available in the United States). In addition, the aspartate aminotransferase-to-platelet ratio (APRI) has also been studied. The APRI has the advantage

All the serum tests have limitations: (a) they typically reflect the rate of matrix turnover, not deposition, and thus tend to be more elevated when there is high inflammatory activity. By contrast, extensive matrix deposition can go undetected if there is minimal inflammation. (b) None of the markers are liver specific, and concurrent sites of inflammation may contribute to serum levels. (c) Serum levels are affected by clearance rates, which may be impaired due to either sinusoidal endothelial cell dysfunction or impaired biliary excretion. (d) They are

**7. Tests of fibrosis**

**7.1. Noninvasive laboratory tests**

84 Recent Advances in Liver Diseases and Surgery

surrogates, not biomarkers [40].

Fibroscan can quantify fibrosis in the liver by means of elastography. Tissue elasticity is acquired through pulse-echo ultrasound, measuring shear wave velocity, the S-wave. The wave travels faster in less elastic and stiff livers. Results of liver elasticity are expressed in kilopascals (kPa). The scan can be performed easily; it is inexpensive and produces no side effects. The position of the patient is similar to when performing a liver biopsy, that is, on the back, with the right hand under the head. Patients only feel the probe pressure in the intercostal space without anticipated pain. It is possible to measure liver elasticity from different angles in the right as well as the left lobe. A liver stiffness measurement using Fibroscan is reprodu‐ cible and independent of the operator, and explores a volume of liver parenchyma, which can be approximated to a cylinder of 1 cm in diameter and 4 cm in length. This volume is 100 times larger than the biopsy specimen volume and is thus much more representative of the entire hepatic parenchyma. Some extensive studies have demonstrated that the measurement of liver stiffness with Fibroscan is a good alternative for liver biopsy. The amount of fibrosis can be quantified very easily and reliably and is feasible in more than 95% of the patients. Obesity, ascites, and narrow intercostal spaces are physiological boundaries that can hamper the accuracy of the test. Acute hepatitis and liver congestion as in cardiac failure can cause false high scores, and they need to be ruled out before carrying out Fibroscan. Sometimes it may be virtually impossible to take measurements in such patients [41, 42]. Fibroscan value ranged from 2.4 to 75.5 kPa with a cutoff value of 7.1 kPa for *F* ≥ 2, 9.5 kPa for *F* ≥3, and 12.5 kPa for *F* = 4 (according to Metavir histological classification system) [41, 43]. One of the studies comparing elastography to histological examination on 327 patients concluded that liver stiffness measurements and fibrosis grades correlated well, with increasing reliability in more extensive fibrosis (*F* ≥ 3) or cirrhosis. It was impossible to determine a cutoff value to differ‐ entiate between F0 and F1 by Fibroscan [41,44].

#### **7.3. Liver biopsy**

Percutaneous liver biopsy is the gold standard for grading and staging of liver disease, which can help to determine the extent of progress of hepatic fibrosis and inflammation. It is important in clinical practice, where it may reflect the severity of liver disease and predict response to treatment. Liver biopsy is an invasive procedure associated with discomfort and, in rare cases, with serious complications. The accuracy of liver biopsy is limited and prone to sampling error and interpretational variability. Although this procedure continues to be recommended, current practice is changing for two main reasons: first, treatment is being shown to be more effective, and second, biochemical tests, serological tests, and elastograms can all provide a great deal of information on disease progression. Pathologists can increase the importance and utility of liver biopsy in chronic hepatitis C, providing information not only on the stage of fibrosis and necro-inflammatory activity but also on the grade of steatosis and iron accumulation, which are implicated in disease progression. Moreover, other diseases, such as steatohepatitis and hereditary hemochromatosis can be identified by liver biopsy. Nevertheless, the use of serological and radiological tests will reduce the indications for liver biopsy [45].
