Controlled attenuation parameter for evaluating liver steatosis in chronic viral hepatitis

WFUMB Guidelines/Guidance on Liver Multiparametric Ultrasound. Part 2: Guidance on Liver Fat Quantification

The World Federation for Ultrasound in Medicine and Biology (WFUMB) has promoted the development of this document on multiparametric ultrasound. Part 2 is a guidance on the use of the available tools for the quantification of liver fat content with ultrasound. These are attenuation coefficient, backscatter coefficient, and speed of sound. All of them use the raw data of the ultrasound beam to estimate liver fat content. This guidance has the aim of helping the reader in understanding how they work and interpret the results. Confounding factors are discussed and a standardized protocol for measurement acquisition is suggested to mitigate them. The recommendations were based on published studies and experts' opinion but were not formally graded because the body of evidence remained low at the time of drafting this document.

US Quantification of Liver Fat: Past, Present, and Future

Fatty liver disease has a high and increasing prevalence worldwide, is associated with adverse cardiovascular events and higher long-term medical costs, and may lead to liver-related morbidity and mortality. There is an urgent need for accurate, reproducible, accessible, and noninvasive techniques appropriate for detecting and quantifying liver fat in the general population and for monitoring treatment response in at-risk patients. CT may play a potential role in opportunistic screening, and MRI proton-density fat fraction provides high accuracy for liver fat quantification; however, these imaging modalities may not be suited for widespread screening and surveillance, given the high global prevalence. US, a safe and widely available modality, is well positioned as a screening and surveillance tool. Although well-established qualitative signs of liver fat perform well in moderate and severe steatosis, these signs are less reliable for grading mild steatosis and are likely unreliable for detecting subtle changes over time. New and emerging quantitative biomarkers of liver fat, such as those based on standardized measurements of attenuation, backscatter, and speed of sound, hold promise. Evolving techniques such as multiparametric modeling, radiofrequency envelope analysis, and artificial intelligence-based tools are also on the horizon. The authors discuss the societal impact of fatty liver disease, summarize the current state of liver fat quantification with CT and MRI, and describe past, currently available, and potential future US-based techniques for evaluating liver fat. For each US-based technique, they describe the concept, measurement method, advantages, and limitations. © RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Ultrasound-Based Diagnostic Methods: Possible Use in Fatty Liver Disease Area

Liver steatosis is a chronic liver disease that is becoming one of the most important global health problems, due to its direct connection with metabolic syndrome, its significant impact on patients' socioeconomic status and frailty, and the occurrence of advanced chronic liver disease. In recent years, there has been rapid technological progress in the ultrasound-based diagnostics field that can help us to quantitatively assess liver steatosis, including continuous attenuation parameters in A and B ultrasound modes, backscatter coefficients (e.g., speed of sound) and ultrasound envelope statistic parametric imaging. The methods used in this field are widely available, have favorable time and financial profiles, and are well accepted by patients. Less is known about their reliability in defining the presence and degree of liver steatosis. Numerous study reports have shown the methods' favorable negative and positive predictive values in comparison with reference investigations (liver biopsy and MRI). Important research has also evaluated the role of these methods in diagnosing and monitoring non-alcoholic fatty liver disease (NAFLD). Since NAFLD is becoming the dominant global cause of liver cirrhosis, and due to the close but complex interplay of liver steatosis with the coexistence of liver fibrosis, knowledge regarding NAFLD's influence on the progression of liver fibrosis is of crucial importance. Study findings, therefore, indicate the possibility of using these same diagnostic methods to evaluate the impact of NAFLD on the patient's liver fibrosis progression risk, metabolic risk factors, cardiovascular complications, and the occurrence of hepatocellular carcinoma. The mentioned areas are particularly important in light of the fact that most of the known chronic liver disease etiologies are increasingly intertwined with the simultaneous presence of NAFLD.

Quantification of Liver Fat Content with the iATT Algorithm: Correlation with Controlled Attenuation Parameter

Background: The primary aim of our study was to assess the correlation between an improved version of the attenuation coefficient available on the Arietta 850 ultrasound system (iATT, Fujifilm Healthcare, Tokyo, Japan) and controlled attenuation parameter (CAP). The secondary aim was to assess whether focusing only on iATT acquisition without following the strict protocol for liver stiffness measurements would affect iATT measurement. Methods: Consecutive individuals were enrolled. Pearson’s r was used to test the correlation between ATT and CAP values. The concordance between iATT and CAP was tested using Lin’s concordance correlation coefficient (CCC). Results: 354 individuals (203 males, 151 females) were studied. The overall Pearson correlation between CAP and iATT values obtained following or not following the liver stiffness measurement protocol, respectively, were r = 0.73 and r = 0.71. The correlation was affected by the interquartile range/median (IQR/M) of the 10 measurements: it was r = 0.75 for IQR/M ≤ 15% and r = 0.60 for IQR/M > 15%. CCC showed that there was a moderate to good concordance between iATT and CAP values. Conclusion: iATT shows a strong correlation with CAP that does not decrease when the protocol for liver stiffness acquisition is not followed. The correlation between iATT and CAP values is higher when the IQR/M ≤ 15%.

Ultrasound-Based Quantification of Fibrosis and Steatosis with a New Software Considering Transient Elastography as Reference in Patients with Chronic Liver Diseases

The goal of this study was to evaluate the performance of two new ultrasound-based techniques (ShearWave PLUS elastography [2-D-SWE PLUS], SSp PLUS Imaging [SSp PLUS]) implemented on the Aixplorer Mach 30 ultrasound system (Supersonic Imagine, Aix-en-Provence, France) for the non-invasive assessment of liver steatosis and fibrosis, using transient elastography (TE) with the controlled attenuation parameter (CAP) as reference. This monocentric cross-sectional study included 133 consecutive adult patients with chronic hepatopathies. Liver stiffness and steatosis were evaluated in the same session using the techniques mentioned above. An excellent correlation was observed between liver stiffness measurements obtained with 2-D-SWE PLUS and TE (r = 0.92, p < 0.0001). The best cutoff value of 2-D-SWE PLUS for predicting F≥2 was 6.8 kPa; for F≥3, 8.4 kPa; and for F4, 11 kPa. With respect to steatosis evaluation, a strong negative correlation between CAP and SSp PLUS values (r = -0.70, p < 0.0001) was obtained. The best SSp PLUS cutoff value for predicting steatosis was 1537 m/s.

Conventional ultrasound for diagnosis of hepatic steatosis is better than believed

BACKGROUND

Hepatic steatosis is a condition frequently encountered in clinical practice, with potential progression towards fibrosis, cirrhosis, and hepatocellular carcinoma. Detection and staging of hepatic steatosis are of most importance in nonalcoholic fatty liver disease (NAFLD), a disease with a high prevalence of more than 1 billion individuals affected. Ultrasound (US) is one of the most used noninvasive imaging techniques used in the diagnosis of hepatic steatosis. Detection of hepatic steatosis with US relies on several conventional US parameters, which will be described. US is the first-choice imaging in adults at risk for hepatic steatosis. The use of some scoring systems may add additional accuracy especially in assessing the severity of hepatic steatosis.

SUMMARY

In the presented paper, we discuss screening and risk stratification, ultrasound features for diagnosing hepatic steatosis, B-mode criteria, focal fatty patterns and Doppler features of the hepatic vessels, and the value of the different US signs for the diagnosis of liver steatosis including classifying the severity of steatosis using different US scores. Limitations of conventional B-mode and Doppler features in the evaluation of hepatic steatosis are also discussed, including those in grading and assessing the complications of steatosis, namely fibrosis and nonalcoholic steatohepatitis.

KEY MESSAGES

Ultrasound is the first-line imaging examination for the screening and follow-up of patients with liver steatosis. The use of some scoring systems may add additional accuracy in assessing the severity of steatosis. Conventional B-mode and Doppler ultrasound have limitations in grading and assessing the complications of steatosis.

Noninvasive Assessment of Hepatitis C Virus Infected Patients Using Vibration-Controlled Transient Elastography

Chronic infection with hepatitis C virus (HCV) is one of the leading causes of cirrhosis and hepatocellular carcinoma (HCC). Surveillance of these patients is an essential strategy in the prevention chain, including in the pre/post-antiviral treatment states. Ultrasound elastography techniques are emerging as key methods in the assessment of liver diseases, with a number of advantages such as their rapid, noninvasive, and cost-effective characters. The present paper critically reviews the performance of vibration-controlled transient elastography (VCTE) in the assessment of HCV patients. VCTE measures liver stiffness (LS) and the ultrasonic attenuation through the embedded controlled attenuation parameter (CAP), providing the clinician with a tool for assessing fibrosis, cirrhosis, and steatosis in a noninvasive manner. Moreover, standardized LS values enable proper staging of the underlying fibrosis, leading to an accurate identification of a subset of HCV patients that present a high risk for complications. In addition, VCTE is a valuable technique in evaluating liver fibrosis prior to HCV therapy. However, its applicability in monitoring fibrosis regression after HCV eradication is currently limited and further studies should focus on extending the boundaries of VCTE in this context. From a different perspective, VCTE may be effective in identifying clinically significant portal hypertension (CSPH). An emerging prospect of clinical significance that warrants further study is the identification of esophageal varices. Our opinion is that the advantages of VCTE currently outweigh those of other surveillance methods.

Quantification of Liver Fibrosis, Steatosis, and Viscosity Using Multiparametric Ultrasound in Patients with Non-Alcoholic Liver Disease: A "Real-Life" Cohort Study

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. This study aimed to evaluate the performance of four ultrasound-based techniques for the non-invasive multiparametric (MPUS) assessment of liver fibrosis (LF), steatosis (HS), and inflammation in patients with NAFLD. We included 215 consecutive adult patients with NAFLD (mean age: 54.9 ± 11.7; 54.5% were male), in whom LF, HS, and viscosity were evaluated in the same session using four new ultrasound-based techniques embedded on the Aixplorer MACH 30 system: ShearWave Elastography (2D-SWE.PLUS), Sound Speed Plane-wave UltraSound (SSp.PLUS), Attenuation Plane-wave UltraSound (Att.PLUS), and Viscosity Plane-wave UltraSound (Vi.PLUS). Transient Elastography (TE) with Controlled Attenuation Parameter (CAP) (FibroScan) were considered as control. All elastographic measurements were performed according to guidelines. Valid liver stiffness measurements (LSM) were obtained in 98.6% of patients by TE, in 95.8% of patients by 2D-SWE.PLUS/Vi.PLUS, and in 98.1% of patients by Att.PLUS/SSp.PLUS, respectively. Therefore, 204 subjects were included in the final analysis. A strong correlation between LSMs by 2D-SWE.PLUS and TE (r = 0.89) was found. The best 2D-SWE.PLUS cut-off value for the presence of significant fibrosis (F ≥ 2) was 7 kPa. Regarding steatosis, SSp.PLUS correlated better than Att.PLUS with CAP values: (r = −0.74) vs. (r = 0.45). The best SSp.PLUS cut-off value for predicting the presence of significant steatosis was 1524 m/s. The multivariate regression analysis showed that Vi.PLUS values were associated with BMI and LSM by 2D-SWE.PLUS. In conclusion, MPUS was useful for assessing fibrosis, steatosis, and inflammation in a single examination in patients with NAFLD.

Controlled Attenuation Parameter for Quantification of Steatosis: Which Cut-Offs to Use?

Chronic liver diseases (CLDs) are a public health problem, even if frequently they are underdiagnosed. Hepatic steatosis (HS), encountered not only in nonalcoholic fatty liver disease (NAFLD) but also in chronic viral hepatitis, alcoholic liver disease, etc., plays an important role in fibrosis progression, regardless of CLD etiology; thus, detection and quantification of HS are imperative. Controlled attenuation parameter (CAP) feature, implemented in the FibroScan® device, measures the attenuation of the US beam as it passes through the liver. It is a noninvasive technique, feasible and well accepted by patients, with lower costs than other diagnostic techniques, with acceptable accuracy for HS quantification. Multiple studies have been published regarding CAP performance to quantify steatosis, but due to the heterogeneity of CLD etiologies, of steatosis prevalence, etc., it had widely variable calculated cut-off values, which in turn limited the day-to-day utility of CAP measurements in clinical practice. This paper reviews published studies trying to suggest cut-off values usable in clinical practice.

Quantitative assessment of liver steatosis using ultrasound controlled attenuation parameter (Echosens)

Controlled attenuation parameter (CAP) is the algorithm available on the FibroScan system (Echosens, France) for quantification of liver steatosis. It assesses the ultrasound beam attenuation, which is directly related to liver fat content. The inter-observer reproducibility of the technique is high, with a reported concordance correlation coefficient of 0.82. Specific quality criteria for CAP measurements are not clearly defined yet, and there are conflicting results in the literature. Using liver biopsy as the reference standard, several studies have assessed the CAP performance in grading liver steatosis, and have reported that values are not affected by liver fibrosis. The cutoff for detection of liver steatosis reported in the literature ranges from 222 decibels per meter (dB/m) in a cohort of patients with chronic hepatitis C to 294 dB/m in a meta-analysis of nonalcoholic fatty liver disease (NAFLD) patients. CAP has been used as a tool to noninvasively evaluate the prevalence of NAFLD in groups at risk or in the general population; however, it should be underscored that different CAP cutoffs for steatosis detection (S > 0) were used in different studies, and this limits the robustness of the findings. CAP, alone or combined with other noninvasive indices or biomarkers, has been proposed as a tool for assessing nonalcoholic steatohepatitis or as a noninvasive predictor of prognosis in patients with chronic liver disease. CAP is easy to perform and has become a point-of-care technique. However, there is a large overlap of values between consecutive grades of liver steatosis, and cutoffs are not clearly defined.

Controlled attenuation parameter value-based diagnostic algorithm improves the accuracy of liver stiffness measurement in chronic hepatitis B patients

Liver stiffness measurement (LSM) frequently overestimates the severity of liver fibrosis because of steatosis. However, the impact of the controlled attenuation parameter (CAP) on liver stiffness cutoff values remains unknown; CAP was used to quantify and diagnose the severity of hepatic steatosis. The study was conducted to determine the effect of CAP on liver stiffness cutoff values in chronic hepatitis B (CHB) patients. A retrospective cross-sectional study was performed in liver biopsy-proven CHB patients. The median LSM (kPa) in the elevated CAP group was higher than that in the normal CAP group at the same fibrosis stage. For S2-4, the area under the receiver operating characteristic (AUROC) curve of LSM was 0.78 and 0.72 in the normal and elevated CAP groups, respectively. When a cutoff value of 8.9 kPa was used, the diagnostic accuracy was 77.82% and 63.41% in the normal and elevated CAP groups, respectively. Compared with the alanine transaminase (ALT)-based LSM algorithm, the CAP-based LSM algorithm had a similar correct diagnosis rate (33.64% vs. 33.94%, respectively) but a lower misdiagnosis rate (16.97% vs. 20.30%, respectively). The new CAP-based LSM diagnostic algorithm will improve the diagnostic accuracy of liver fibrosis in CHB patients.

Usefulness of Different Imaging Modalities in Evaluation of Patients with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are becoming some of the major health problems in well-developed countries, together with the increasing prevalence of obesity, metabolic syndrome, and all of their systemic complications. As the future prognoses are even more disturbing and point toward further increase in population affected with NAFLD/NASH, there is an urgent need for widely available and reliable diagnostic methods. Consensus on a non-invasive, accurate diagnostic modality for the use in ongoing clinical trials is also required, particularly considering a current lack of any registered drug for the treatment of NAFLD/NASH. The aim of this narrative review was to present current information on methods used to assess liver steatosis and fibrosis. There are several imaging modalities for the assessment of hepatic steatosis ranging from simple density analysis by computed tomography or conventional B-mode ultrasound to magnetic resonance spectroscopy (MRS), magnetic resonance imaging proton density fat fraction (MRI-PDFF) or controlled attenuation parameter (CAP). Fibrosis stage can be assessed by magnetic resonance elastography (MRE) or different ultrasound-based techniques: transient elastography (TE), shear-wave elastography (SWE) and acoustic radiation force impulse (ARFI). Although all of these methods have been validated against liver biopsy as the reference standard and provided good accuracy, the MRS and MRI-PDFF currently outperform other methods in terms of diagnosis of steatosis, and MRE in terms of evaluation of fibrosis.

Ultrasound-based techniques for the diagnosis of liver steatosis

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of diffuse liver disease. An accurate estimate of the fat in the liver is important in the diagnostic work-up of patients with NAFLD because the degree of liver steatosis is linked to the metabolic syndrome and the cardiovascular risk. Ultrasound (US) B-mode imaging allows to subjectively estimate the fatty infiltration in the liver; however, it has a low performance for the detection of mild steatosis. Quantitative US is based on the analysis of the radiofrequency echoes detected by an US system, and it allows to calculate a backscatter coefficient or an attenuation coefficient or the sound speed. The estimation of the backscatter coefficient is rather cumbersome and requires the use of a phantom for addressing all sources of variability. Controlled attenuation parameter (CAP) available on the FibroScan^® system (Echosens, France) measures the attenuation of the US beam. CAP is accurate in grading fatty infiltration-even though there is an overlap between consecutive grade of liver steatosis-and the values are not influenced by liver fibrosis. Several US manufacturers are developing or have already developed software for quantifying the attenuation of the US beam. Preliminary results show that proprietary technologies implemented in US systems seem more accurate than CAP for grading liver steatosis. Another available method for quantifying liver steatosis is based on the computation of the sound speed and the initial results appear promising.

Liver Ultrasound Elastography: An Update to the World Federation for Ultrasound in Medicine and Biology Guidelines and Recommendations

The World Federation for Ultrasound in Medicine and Biology has produced these guidelines for the use of elastography techniques in liver diseases. For each available technique, the reproducibility, results and limitations are analyzed, and recommendations are given. This set of guidelines updates the first version, published in 2015. Since the prior guidelines, there have been several advances in technology. The recommendations are based on the international published literature, and the strength of each recommendation is judged according to the Oxford Centre for Evidence-Based Medicine. The document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of liver diseases.

Quantitative Hepatic Fat Quantification in Non-alcoholic Fatty Liver Disease Using Ultrasound-Based Techniques: A Review of Literature and Their Diagnostic Performance

Non-alcoholic fatty liver disease is a condition that is characterized by the presence of >5% fat in the liver and affects more than one billion people worldwide. If adequate and early precautions are not taken, non-alcoholic fatty liver disease can progress to cirrhosis and death. The current reference standard for detecting hepatic steatosis is a liver biopsy. However, because of the potential morbidity associated with liver biopsies, non-invasive imaging biomarkers have been extensively investigated. Magnetic resonance imaging-based methods have proven accuracy in quantifying liver steatosis; however, these techniques are costly and have limited availability. Ultrasound-based quantitative imaging techniques are increasingly utilized because of their widespread availability, ease of use and relative cost-effectiveness. Several ultrasound-based liver fat quantification techniques have been investigated, including techniques that measure changes in the acoustic properties of the liver caused by the presence of fat. In this review, we focus on quantitative ultrasound approaches and their diagnostic performance in the realm of non-alcoholic fatty liver disease.

Prevalence and predictive factors of moderate/severe liver steatosis in chronic hepatitis C (CHC) infected patients evaluated with controlled attenuation parameter (CAP)

A novel controlled attenuation parameter (CAP) using FibroScan^® has been developed for assessment of liver steatosis. The aim was to evaluate the frequency and associated factors for moderate/severe steatosis evaluated by CAP in CHC patients submitted to transient elastography (TE) by FibroScan^® . CHC patients underwent TE with CAP evaluation. The classification of steatosis was defined as: CAP < 222 dB/m  =  S0; CAP ≥ 222 dB/m and <233dB/m  =  S1; ≥233 dB/m < 290dB/m  =  S2 and >= 290 dB/m  =  S3. The prevalence of moderate/severe steatosis (CAP ≥ S2) and the related independent factors were identified by a logistic regression analysis. A significance level of 5% was adopted. 1104 CHC patients, 85% genotype-1 were included (mean age 55 ± 11 years; 46% male, mean BMI 25 ± 4 Kg/m² ). Systemic arterial hypertension and type 2 diabetes mellitus prevalences were 39% and 17%, respectively. Liver stiffness measurement ≥ 9.5 kPa was observed in 39% of patients and steatosis was identified in 50% (S1 = 7%, S2 = 28% and S3 = 15%). The variables independently associated with moderate/severe steatosis were: male gender (OR=1.35; P = .037; 95% CI:1.01-1.81); systemic arterial hypertension (OR=1.57; P = .002; 95% CI:1.17-2.10) and BMI (OR=1.17; P < .01;95% CI:1.12-1.22). In conclusion, when CAP was adopted as a tool to detect steatosis, genotype 1 CHC patients presented a high prevalence of moderate/advanced steatosis. In these patients, liver steatosis was associated mostly to metabolic factors (arterial hypertension and high BMI).

Predictors of treatment efficacy and liver stiffness changes following therapy with Sofosbuvir plus Ribavirin in patients infected with HCV genotype 2

While the combination therapy of ribavirin (RBV) and sofosbuvir (SOF) is effective in genotype 2 HCV infection, the predictors of treatment efficacy and posttreatment changes in α-fetoprotein (AFP) and liver stiffness (markers of hepatocellular carcinoma), remain unclear. In this study, 302 patients with chronic HCV genotype 2 infection were treated with SOF (400 mg) plus RBV (400-1000 mg; based on body weight) for 12 weeks. We evaluated the efficacy and safety of treatment, as well as measured serum AFP, liver stiffness, and controlled attenuation parameter (CAP, a surrogate marker of steatosis) at baseline and within 48 weeks of treatment completion. The intention-to-treat analysis showed a sustained virological response (SVR) rate of 95.7%. None of the patients discontinued treatment due to side effects. Multivariate analysis identified pretreatment (no treatment with interferon), level of AFP (AFP; <10 μg/L), and RBV/body weight (BW) ratio (≥9.0 mg/kg) as independent predictors of SVR. The SVR rate in patients with two predictors of poor response (AFP ≥10 μg/L and RBV/BW ratio <9.0 mg/kg) was significantly lower than in other patients. In the SVR group, posttreatment AFP level and liver stiffness were significantly lower than at baseline. CAP tended to be higher after treatment than at baseline in all patients. SOF plus RBV combination therapy achieved a high SVR rate and was safe in HCV genotype 2 infected patients. Treatment reduced AFP levels and improved liver stiffness, but increased CAP.

A comparison of hepatic steatosis index, controlled attenuation parameter and ultrasound as noninvasive diagnostic tools for steatosis in chronic hepatitis B

AIMS

To evaluate the value of noninvasive tools for diagnosis of hepatic steatosis in patients with chronic hepatitis B (CHB).

METHODS

Consecutive treatment-naïve patients with CHB with body mass index less than 30kg/m² who underwent liver biopsy, ultrasound and FibroScan^® were enrolled. The diagnostic performance of controlled attenuation parameter (CAP), hepatic steatosis index (HSI) and ultrasound for hepatic steatosis compared with liver biopsy was assessed. The areas under receiver operating characteristics curves (AUROCs) were calculated to determine the diagnostic efficacy, with comparisons using the DeLong test.

RESULTS

CAP and HSI accuracies were significantly higher than that of ultrasound to detect patients with biopsy-proven mild steatosis (S1, 65.3%, 56.5%, respectively, vs. 17.7%, χ²=46.305, 31.736, both P<0.05)and moderate-severe (S2-3) steatosis (92.3%, 100%, respectively, vs. 53.8%, χ²=4.887, 7.800, P=0.037, 0.007, respectively). Both CAP and HSI had lower underestimation rates of steatosis grade than ultrasound (12%, 14.8%, respectively, vs. 29.5%, χ²=9.765, 6.452; P<0.05 for both), but they exhibited higher overestimation rates (30.5%, 38.2%, respectively, vs. 12.4%, χ²=39.222, 70.986; both P<0.05). The AUROCs of CAP and HSI were 0.780 (95% confidence intervals [CIs] 0.735-0.822) and 0.655 (95%CI 0.604-0.704) for S ≥1, 0.932 (95%CI 0.902-0.956) and 0.755 (95%CI 0.707-0.799) for S ≥2, 0.990 (95%CI 0.974-0.998) and 0.786 (95% CI 0.740-0.827) for S3, respectively.

CONCLUSION

CAP might be more accurate for detecting hepatic steatosis than HSI and ultrasound in patients with CHB, but further studies are needed to reduce the overestimation rates.

Individual patient data meta-analysis of controlled attenuation parameter (CAP) technology for assessing steatosis

BACKGROUND & AIMS

The prevalence of fatty liver underscores the need for non-invasive characterization of steatosis, such as the ultrasound based controlled attenuation parameter (CAP). Despite good diagnostic accuracy, clinical use of CAP is limited due to uncertainty regarding optimal cut-offs and the influence of covariates. We therefore conducted an individual patient data meta-analysis.

METHODS

A review of the literature identified studies containing histology verified CAP data (M probe, vibration controlled transient elastography with FibroScan®) for grading of steatosis (S0-S3). Receiver operating characteristic analysis after correcting for center effects was used as well as mixed models to test the impact of covariates on CAP. The primary outcome was establishing CAP cut-offs for distinguishing steatosis grades.

RESULTS

Data from 19/21 eligible papers were provided, comprising 3830/3968 (97%) of patients. Considering data overlap and exclusion criteria, 2735 patients were included in the final analysis (37% hepatitis B, 36% hepatitis C, 20% NAFLD/NASH, 7% other). Steatosis distribution was 51%/27%/16%/6% for S0/S1/S2/S3. CAP values in dB/m (95% CI) were influenced by several covariates with an estimated shift of 10 (4.5-17) for NAFLD/NASH patients, 10 (3.5-16) for diabetics and 4.4 (3.8-5.0) per BMI unit. Areas under the curves were 0.823 (0.809-0.837) and 0.865 (0.850-0.880) respectively. Optimal cut-offs were 248 (237-261) and 268 (257-284) for those above S0 and S1 respectively.

CONCLUSIONS

CAP provides a standardized non-invasive measure of hepatic steatosis. Prevalence, etiology, diabetes, and BMI deserve consideration when interpreting CAP. Longitudinal data are needed to demonstrate how CAP relates to clinical outcomes.

LAY SUMMARY

There is an increase in fatty liver for patients with chronic liver disease, linked to the epidemic of the obesity. Invasive liver biopsies are considered the best means of diagnosing fatty liver. The ultrasound based controlled attenuation parameter (CAP) can be used instead, but factors such as the underlying disease, BMI and diabetes must be taken into account. Registration: Prospero CRD42015027238.

Controlled attenuation parameter using the FibroScan® XL probe for quantification of hepatic steatosis for non-alcoholic fatty liver disease in an Asian population

BACKGROUND

The FibroScan® XL probe reduces failure of liver stiffness measurement (LSM) and unreliable results in obese patients.

OBJECTIVE

The objective of this article is to evaluate the accuracy of controlled attenuation parameter (CAP) obtained using the XL probe for the estimation of hepatic steatosis in patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

Adult NAFLD patients with a liver biopsy within six months were included and were examined with the FibroScan® M and XL probes. Histopathological findings were reported according to the Non-Alcoholic Steatohepatitis Clinical Research Network Scoring System. Participants who did not have fatty liver on ultrasonography were recruited as controls.

RESULTS

A total of 57 NAFLD patients and 22 controls were included. The mean age of the NAFLD patients and controls was 50.1 ± 10.4 years and 20.2 ± 1.3 years, respectively (p = 0.000). The mean body mass index was 30.2 ± 5.0 kg per m2 and 20.5 ± 2.4 kg per m2, respectively (p = 0.000). The distribution of steatosis grades were: S0, 29%; S1, 17%; S2, 35%; S3, 19%. The AUROC for estimation of steatosis grade ≥ S1, S2 and S3 was 0.94, 0.80 and 0.69, respectively, using the M probe, and 0.97, 0.81 and 0.67, respectively, using the XL probe.

CONCLUSION

CAP obtained using the XL probe had similar accuracy as the M probe for the estimation of hepatic steatosis in NAFLD patients.

The clinical value of controlled attenuation parameter for the noninvasive assessment of liver steatosis

BACKGROUND & AIMS

Ultrasound is the imaging modality most widely utilized in the general population for diagnostic purposes. Controlled attenuation parameter is a novel noninvasive method for assessing steatosis. Our aim was to investigate whether the clinical value of controlled attenuation parameter in patients referred for abdominal ultrasound examinations is affected by liver fibrosis.

METHODS

Consecutive patients referred for abdominal ultrasound examinations were enrolled. Controlled attenuation parameter and liver stiffness were assessed with the FibroScan (Echosens, France). Liver fibrosis was staged according to published cutoffs of liver stiffness measurements. Pearson's or Spearman's rank correlation coefficient was used to test the association between two study variables. Optimal cutoff of controlled attenuation parameter for diagnosing liver steatosis (S≥2) was 256 dB/m. The diagnostic performance and accuracy of dichotomized controlled attenuation parameter, ultrasound and body mass index were analysed using the imperfect gold standard methodology.

RESULTS

A total of 726 subjects (464 males and 262 females) were studied. Five hundred and eight-nine (81.1%) patients were affected by chronic viral hepatitis. Correlation of controlled attenuation parameter with ultrasound score was 0.48 and 0.57 in patients with and without chronic viral hepatitis respectively. In patients with chronic viral hepatitis, ultrasound, dichotomized controlled attenuation parameter and body mass index showed performance of 58.2%, 82.3% and 46.7%, respectively, whereas in patients without chronic viral hepatitis, the performance was 86.4%, 68.6% and 48.6% respectively.

CONCLUSIONS

In patients with chronic viral hepatitis and advanced liver fibrosis, controlled attenuation parameter performs better than ultrasound for assessing liver steatosis, whereas in patients without viral hepatitis and with nonsignificant liver disease ultrasound shows the best performance.

Non-invasive diagnosis of hepatic steatosis

Non-invasive diagnosis and quantification of hepatic steatosis rely on two different but complementary approaches: biomarkers or imaging techniques, either ultrasound-based such as liver ultrasonography and controlled attenuation parameter (CAP), or computed tomography (CT) and magnetic resonance imaging (MRI). Scores for the detection of steatosis have not gained much popularity in clinical practice so far. CAP, using the M probe, is the most promising technique but needs to be implemented with the XL probe and compared to ultrasound that, despite its limitations, remains the most widely used method. CT, owing to its low sensitivity and the fact that it involves a potential radiation hazard, is inappropriate. Finally, proton density fat fraction measurement by MRI is currently the most accurate and sensitive imaging method, simpler and more practical than magnetic resonance spectroscopy, but restricted, up to now, just to research and clinical trials.

The common PNPLA3 variant p.I148M is associated with liver fat contents as quantified by controlled attenuation parameter (CAP)

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is becoming the most prevalent liver disorder. The PNPLA3 (adiponutrin) variant p.I148M has been identified as common genetic modifier of NAFLD. Our aim was to assess the relationships between genetic risk and non-invasively measured liver fat content.

METHODS

Hepatic steatosis was quantified by transient elastography, using the controlled attenuation parameter (CAP) in 174 patients with chronic liver diseases (50% women, age 18-77 years). In addition, a cohort of 174 gender-matched healthy controls (50% women, age 32-77 years) was recruited. The PNPLA3 mutation as well as the novel NAFLD-predisposing genetic variant (TM6SF2 p.E167K) were genotyped with allele-specific probes.

RESULTS

The PNPLA3 genotype correlated significantly (P = 0.001) with hepatic CAP measurements. The p.148M risk allele increased the odds of developing liver steatosis (OR = 2.39, P = 0.023). In multivariate models, BMI and PNPLA3 mutation were both independently associated with CAP values (P < 0.001 and P = 0.007, respectively). Carriers of the TM6SF2 risk allele presented with increased aminotransferase activities (ALT: P = 0.007, AST: P = 0.004), but the presence of this variant did not affect CAP values.

CONCLUSIONS

The PNPLA3 p.I148M variant represents the most important prosteatotic genetic risk factor. NAFLD carriers of this variant should be followed up carefully, with elastography and CAP being ideally suited for this purpose.

Liver Steatosis Assessed by Controlled Attenuation Parameter (CAP) Measured with the XL Probe of the FibroScan: A Pilot Study Assessing Diagnostic Accuracy

To assess liver steatosis, the controlled attenuation parameter (CAP; giving an estimate of ultrasound attenuation ∼3.5 MHz) is available with the M probe of the FibroScan. We report on the adaptation of the CAP for the FibroScan XL probe (center frequency 2.5 MHz) without modifying the range of values (100-400 dB/m). CAP validation was successfully performed on Field II simulations and on tissue-mimicking phantoms. In vivo performance was assessed in a cohort of 59 patients spanning the range of steatosis. In vivo reproducibility was good and similar with both probes. The area under receiver operative characteristic curve was equal to 0.83/0.84 and 0.92/0.91 for the M/XL probes to detect >2% and >16% liver fat, respectively, as assessed by magnetic resonance imaging. Patients can now be assessed simultaneously for steatosis and fibrosis using the FibroScan, regardless of their morphology.

Noninvasive assessment of alcoholic liver disease using unidimensional transient elastography (Fibroscan®)

Unidimensional transient elastography (TE) is a noninvasive technique, which has been increasingly used in the assessment of diffuse liver diseases. This paper focuses on reviewing the existing data on the use of TE in the diagnosis of fibrosis and in monitoring disease progression in alcoholic liver disease, on the factors that may influence the result of fibrosis prediction, and last but not least, on its potential use in assessing the steatosis degree. Therefore, this field is far from being exhausted and deserves more attention. Further studies are required, on large groups of biopsied patients, in order to find answers to all the remaining questions in this field.

Controlled attenuation parameter for assessment of hepatic steatosis grades: a diagnostic meta-analysis

AIM

to evaluate the performance and accuracy of Controlled attenuation parameter CAP for hepatic steatosis detection.

METHODS

PubMed, EBSCO, Elsevier Science, Ovid, and Wiley were selected to search studies until August 31, 2014. Quality Assessment of Diagnostic Accuracy Studies checklist was used to assess the quality of included studies. Heterogeneity was evaluated using Q test. Sensitivity, specificity, diagnostic odds ratio (DOR), and the area under curve (AUC) with its 95% confidence intervals (CIs) were calculated to evaluate the accuracy of CAP for assessment of hepatic steatosis stage (≥ S1, ≥ S2 and ≥ S3).

RESULTS

Totally 11 studies (13 cohorts) with high methodological qualities were identified. The summary point estimations with 95% CIs of sensitivity, specificity, AUC and DORs were 0.78 (0.71, 0.84), 0.79 (0.70, 0.86), 0.86 (0.82, 0.88), and 14 (7, 27) for ≥ S1; 0.82 (0.74, 0.88), 0.79 (0.73, 0.85), 0.88 (0.85, 0.90) and 18 (10, 30) for ≥ S2; 0.86 (0.82, 0.89), 0.89 (0.86, 0.92), 0.94 (0.91, 0.96) and 51 (35, 76) for ≥ S3. Significant heterogeneity was found among the studies in ≥ S1 and ≥ S3. Threshold effect was existed in ≥ S3, but not in ≥ S1 and ≥ S2. Publication bias was not existed in ≥ S1 and ≥ S2 except ≥ S3.

CONCLUSION

CAP provides good sensitivity and specificity for detection of ≥ S1, ≥ S2, and ≥ S3 steatosis. However, future studies with large samples are still necessary to confirm the clinical application.

[Non-invasive assessment of fatty liver]

As the result of various harmful effects (infectious agents, metabolic diseases, unhealthy diet, obesity, toxic agents, autoimmune processes) hepatic damage may develop, which can progress towards liver steatosis, and fibrosis as well. The most common etiological factors of liver damages are hepatitis B and C infection, alcohol consumption and non-alcoholic fatty liver disease. Liver biopsy is considered as the gold standard for the diagnosis of chronic liver diseases. Due to the dangers and complications of liver biopsy, studies are focused on non-invasive markers and radiological imaging for liver steatosis, progression of fatty liver, activity of the necroinflammation and the severity of the fibrosis. Authors review the possibilities of non-invasive assessment of liver steatosis. The statistical features of the probes (positive, negative predictive values, sensitivity, specificity) are reviewed. The role of radiological imaging is also discussed. Although the non-invasive methods discussed in this article are useful to assess liver steatosis, further studies are needed to validate to follow progression of the diseases and to control therapeutic response.

Correlation of the controlled attenuation parameter with indices of liver steatosis in overweight or obese individuals: a pilot study

OBJECTIVE

The aim of this study was to assess the clinical relevance of the controlled attenuation parameter (CAP) by analyzing the correlations between CAP and indirect indices of liver steatosis in obese or overweight individuals.

METHODS

Consecutive participants were prospectively enrolled. BMI, waist circumference, hepatic steatosis index, fatty liver index, percent fat mass and regional fat masses as assessed by dual-energy X-ray absorptiometry (DXA), fat signal fraction as assessed by MRI, and CAP were obtained. Pearson's r coefficient was used to test the correlation between two study variables.

RESULTS

A total of 88 individuals were studied. They included 31 men [age, 50.4 years (12.9 years); BMI, 30.7 kg/m (4.8 kg/m)] and 57 women [age, 49.0 years (12.6 years); BMI, 31.4 kg/m (5.6 kg/m)]. DXA, anthropometric parameters, and fatty liver index were moderately correlated with CAP in men. In women, there was a moderate correlation of CAP with the hepatic steatosis index and anthropometric parameters and only a slight or fair correlation of CAP with DXA parameters. CAP and fat signal fraction showed a good correlation (r=0.65 in men, P=0.002; r=0.68 in women, P=0.0009).

CONCLUSION

Measurement of CAP is a reliable method for noninvasive assessment of liver steatosis, showing a correlation with other indirect markers of central obesity and a good correlation with MRI results.