***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Recurrence of hepatitis C  after liver transplantation ( LT ) is the main cause of graft loss and retransplantation . Frequent liver biopsies are essential to follow-up hepatitis C virus (HCV)-induced liver damage . However , liver biopsy is an invasive and expensive procedure . We evaluated prospect ively the diagnostic accuracy of noninvasive measurement of liver stiffness ( by transient elastography ) to assess the severity of hepatitis C recurrence after LT . For this purpose , we included 124 HCV-infected liver transplant recipients who underwent 169 liver biopsies and 129 hepatic hemodynamic studies with determination of hepatic venous pressure gradient ( HVPG ) .  Simultaneously , patients underwent measurement of liver stiffness . Liver fibrosis was mild ( F0-F1 ) in 96 cases ( 57 % ) and significant ( F2-F4 ) in 73 ( 43 % ) . HVPG was normal ( < 6 mm Hg ) in 69 cases ( 54 % ) and elevated ( > or=6 mm Hg ) in 60 ( 46 % ) . Using a liver stiffness cutoff value of 8.5 kilopascals , the sensitivity , specificity , negative predictive value , and positive predictive value for diagnosis of fibrosis > or = F2 were 90 % , 81 % , 79 % , and 92 % , respectively . The area under the curve ( AUC ) for diagnosis of fibrosis > or = F2 , > or = F3 and F4 were 0.90 , 0.93 , and 0.98 , respectively . There was a close direct correlation between liver stiffness and HVPG ( Pearson coefficient , 0.84 ; P < 0.001 ) and the AUC for diagnosis of portal hypertension ( HVPG > or=6 mm Hg ) was 0.93 . Importantly , none of the individuals with liver stiffness below the cutoff value had either bridging fibrosis ( F3 ) or cirrhosis ( F4 ) or significant portal hypertension ( HVPG > or=10 mm Hg ) . In conclusion , determination of liver stiffness is an extremely valuable tool to assess the severity of HCV recurrence after LT and in reducing the need of follow-up liver biopsies Background : Transient elastography ( FibroScan ) is a new , non-invasive , rapid , and reproducible method allowing evaluation of liver fibrosis by measurement of liver stiffness . In cirrhotic patients , liver stiffness measurements range from 12.5 to 75.5 kPa . However , the clinical relevance of these values is unknown . The aim of this prospect i ve study was to evaluate the accuracy of liver stiffness measurement for the detection of cirrhosis in patients with chronic liver disease . Methods : A total of 711 patients with chronic liver disease were studied . Aetiologies of chronic liver diseases were hepatitis C virus or hepatitis B virus infection , alcohol , non-alcoholic steatohepatitis , other , or a combination of the above aetiologies . Liver fibrosis was evaluated according to the METAVIR score . Results : Stiffness was significantly correlated with fibrosis stage ( r = 0.73 , p<0.0001 ) . Areas under the receiver operating characteristic curve ( 95 % confidence interval ) were 0.80 ( 0.75–0.84 ) for patients with significant fibrosis ( F>2 ) , 0.90 ( 0.86–0.93 ) for patients with severe fibrosis ( F3 ) , and 0.96 ( 0.94–0.98 ) for patients with cirrhosis . Using a cut off value of 17.6 kPa , patients with cirrhosis were detected with a positive predictive value and a negative predictive value ( NPV ) of 90 % . Liver stiffness was significantly correlated with clinical , biological , and morphological parameters of liver disease . With an NPV > 90 % , the cut off values for the presence of oesophageal varices stage 2/3 , cirrhosis Child-Pugh B or C , past history of ascites , hepatocellular carcinoma , and oesophageal bleeding were 27.5 , 37.5 , 49.1 , 53.7 , and 62.7 kPa , respectively . Conclusion : Transient elastography is a promising non-invasive method for detection of cirrhosis in patients with chronic liver disease . Its use for the follow up and management of these patients could be of great interest and should be evaluated further Background This prospect i ve study aim ed to assess the ability of transient elastography to identify histologic parameters , including steatosis , in asymptomatic healthy individuals such as potential liver donors , and to compare these findings with results in liver disease patients . Methods Forty-seven patients with abnormal liver function and /or hepatitis symptoms and 80 living related potential liver donors were consecutively enrolled , and liver biopsy and a Fibroscan test were performed in each subject . Histologic parameters were evaluated according to METAVIR scale by a single pathologist . Results In liver disease patients , stiffness was significantly correlated with fibrosis stage ( Spearman correlation coefficient , 0.700 ; P < 0.001 ) , and the optimal stiffness cutoff values for F ≥ 2 , F ≥ 3 , and F = 4 were 7.35 , 8.85 , and 15.1 kPa respectively . In potential liver donors , however , stiffness was not correlated with fibrosis ( 0.023 ; P = 0.851 ) . In the latter group , the area under the receiver-operating characteristics curve was 0.70 ( 95 % confidence interval , 0.58–0.81 ) , and the optimal stiffness cutoff value was 4.00 for F ≥ 2 , which was lower than that in liver disease patients . Steatosis was not correlated with stiffness ( 0.088 ; P = 0.463 ) in potential liver donors . Conclusions Transient elastography has limited value for detecting steatosis in asymptomatic healthy individuals , and the cutoff value for fibrosis should be reevaluated in these subjects Background The aim of this study was to assess the diagnostic performances of liver stiffness measurement ( LSM ) , ultrasonography ( US ) and their combined use in predicting the extent of hepatic fibrosis . Methods Consecutive patients with chronic hepatitis B ( HBV ) or hepatitis C virus ( HCV ) infections , with indications for liver biopsy , were prospect ively enrolled .  LSM was performed on the same day as biopsy .  US scores , including assessment of liver surface , liver parenchyma , intrahepatic vessels and spleen index , were used to assess the degree of hepatic fibrosis . The pathological findings were used as a reference st and ard and diagnostic accuracy was assessed and compared . Results Three-hundred and twenty patients , including 199 men and 121 women , with a mean age of 50.8 years , were analyzed . There were 214 ( 66.9 % ) HCV patients , 88 ( 27.5 % ) HBV patients and 18 ( 5.6 % ) patients with both HCV and HBV .  LSM correlated significantly with the hepatic fibrosis ( F ) scores , necro-inflammatory activity and US scores in multivariate analysis . The diagnostic accuracy of LSM is significantly superior to US , and equal to combined LSM with US , in the prediction of all HCV-related fibrosis scores . The cut-off value of LSM is 6 kPa for diagnosing F > = 1 , with a positive predictive value of 91 % . Also , the cut-off value is 12 kPa for the prediction of cirrhosis , with a negative predictive value of 94 % . Conclusions LSM is useful for predicting hepatic fibrosis and excluding cirrhosis . A combination of LSM and US does not improve the accuracy in assessing hepatic fibrosis PURPOSE To prospect ively measure liver stiffness with real-time tissue elastography in patients with chronic hepatitis C and to compare the results with those of clinical assessment of fibrosis by using histologic stage as the reference st and ard . MATERIAL S AND METHODS All subjects gave informed consent , and the study was approved by the institutional ethics committee . Seventy hospitalized patients ( 46 men , 24 women ; mean age , 65.5 years ± 11.7 [ st and ard deviation ] ; age range , 33 - 87 years ) with chronic hepatitis C underwent real-time elastography  between January 2009 and September 2009 . Elastography was performed at four liver locations by two independent observers . The elastic ratio ( ratio of the value in the intrahepatic venous small vessels divided by the value in the hepatic parenchyma ) was calculated and was compared with histologic fibrosis stage at liver biopsy . The elastic ratio and clinical fibrosis markers were assessed by using receiver operating characteristic ( ROC ) analysis . The differences between body site and observers were assessed with κ statistics and intraclass correlation coefficients ( ICCs ) .  RESULTS Real-time tissue elastography cutoff values were 2.73 for F of 2 or greater , 3.25 for F of 3 or greater , and 3.93 for F of 4 . No site differences were observed ( κ = 0.835 , ICC = 0.966 ) , and the elastic ratio measurement was correlated between the two examiners ( r(2 ) = 0.869 , P < .0001 ) . The areas under the ROC curves for elastic ratio , hyaluronic acid , type IV collagen , aspartate aminotransferase-to-platelet ratio index , FibroIndex , Forns score , and Hepascore were 0.95 , 0.32 , 0.73 , 0.76 , 0.76 , 0.87 , and 0.70 , respectively ; the elastic ratio performed better than the serum fibrosis markers and other scores . CONCLUSION Real-time tissue elastography is not invasive and could be used to evaluate liver fibrosis in patients with chronic hepatitis C. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100319/-/DC1 BACKGROUND & AIMS Both transient elastography ( TE ) and left lobe liver surface ( LLS ) ultrasound may non-invasively detect cirrhosis ( LC ) . We aim ed to examine the diagnostic value of these methods in patients with a suspicion but not a definite diagnosis of cirrhosis . METHODS We enrolled 90 patients with clinical suspicion of cirrhosis and a strong co-existing differential diagnosis requiring further invasive evaluation . They underwent hepatic venous pressure gradient ( HVPG ) measurement+/-transjugular liver biopsy , LLS and TE . Images of LLS were digitally post-processed to obtain a numerical value ( quantitative LLS , qLLS ) . TE<12kPa was considered to exclude LC , 18kPa diagnosed LC , and 12 - 18kPa indeterminate . Technical failures were considered ' indeterminate ' . Diagnosis of cirrhosis was confirmed by histology ( 84 % ) or by clinical data and HVPG10 mm Hg . Diagnostic accuracy was evaluated by positive and negative likelihood ratios ( + LR and -LR ) . RESULTS Cirrhosis was diagnosed in 44 patients . There were 14 technical failures with TE and 1 with LLS ( p=0.001 ) . TE and LLS had similar diagnostic accuracy but gave complementary information : TE was mildly more accurate than LLS to rule out LC ( -LR : 0.08 vs. 0.10 ) , while it was less accurate to rule it in ( + LR 5.05 vs. 11.15 ) . Their combination offered the best diagnostic performance ( + LR 9.15 ; -LR 0.06 ) . CONCLUSIONS LLS is more technically applicable than TE . In patients with clinical suspicion of cirrhosis , LLS is the best non-invasive method to diagnose cirrhosis , while TE is preferable to rule it out . The combination of both holds the best diagnostic accuracy The course of hepatitis C virus ( HCV ) infection carriers with normal/near-normal aminotransferases ( NALT ) is usually mild ; however , in a few , fibrosis progression occurs . We aim ed to verify whether monitoring by liver biopsy might be replaced by noninvasive methods and to identify factors associated with fibrosis progression in patients with persistently normal alanine aminotransferases . We studied 40 untreated HCV-RNA-positive subjects ( 22 male ; median age , 44 years ) , who underwent two liver biopsies , with a median interval of 78.5 months , during which alanine aminotransferase concentrations ( median number of determinations : 12 ) never exceeded 1.2 times the upper normal limit . Within 9 months from the second biopsy , they were tested by the shear elasticity probe ( Fibroscan ) and the artificial intelligence algorithm FibroTest .  METAVIR fibrosis scores were analyzed in relationship to demographic , clinical , and viral parameters . Weighted kappa analysis was used to verify whether the results of noninvasive methods agreed with histology . Significant fibrosis ( > or = F2 ) , present at the first biopsy in only one patient ( 2.5 % ) , was observed at the second biopsy in 14 patients ( 35 % ) . At multivariate analysis 
    Output:
    
The model was sensitive to the sensitivity and specificity of TE and the prevalence of fibrosis .
CONCLUSIONS TE is an accurate diagnostic method in patients with moderate fibrosis or cirrhosis .
TE is less effective but less expensive than liver biopsy .