Marked difference in liver fat measured by histology vs. magnetic resonance-proton density fat fraction: A meta-analysis

Effects of hepatic fibrosis on the quantification of hepatic steatosis using the controlled attenuation parameter in patients with chronic hepatitis B

PURPOSE

This study assessed the impact of hepatic fibrosis on the diagnostic performance of the controlled attenuation parameter (CAP) in quantifying hepatic steatosis in patients with chronic hepatitis B (CHB).

METHODS

CHB patients who underwent liver stiffness measurement (LSM) and CAP assessment using transient elastography before liver resection between 2019 and 2022 were retrospectively evaluated. Clinical data included body mass index (BMI) and laboratory parameters. The histologically determined hepatic fat fraction (HFF) and fibrosis stages were reviewed by pathologists blinded to clinical and radiologic data. The Pearson correlation coefficient between CAP and HFF was calculated. The diagnostic performance of CAP for significant hepatic steatosis (HFF ≥10%) was assessed using areas under the receiver operating curve (AUCs), stratified by fibrosis stages (F0-1 vs. F2-4). Factors significantly associated with CAP were determined by univariable and multivariable linear regression analyses.

RESULTS

Among 399 CHB patients (median age 59 years; 306 men), 16.3% showed significant steatosis. HFF ranged from 0% to 60%. Of these patients, 9.8%, 19.8%, 29.3%, and 41.1% had fibrosis stages F0-1, F2, F3, and F4, respectively. CAP positively correlated with HFF (r=0.445, P<0.001). The AUC of CAP for diagnosing significant steatosis was 0.786 (95% confidence interval [CI], 0.726 to 0.845) overall, and significantly lower in F2-4 (0.772; 95% CI, 0.708 to 0.836) than in F0-1 (0.924; 95% CI, 0.835 to 1.000) (P=0.006). Multivariable analysis showed that BMI (P<0.001) and HFF (P<0.001) significantly affected CAP, whereas LSM and fibrosis stages did not.

CONCLUSION

CAP evaluations of significant hepatic steatosis are less reliable in CHB patients with significant or more advanced (F2-4) than with no or mild (F0-1) fibrosis.

Accuracy of Controlled Attenuation Parameter for Liver Steatosis in High-Risk Patients for MASLD Using MRI-Proton Density Fat Fraction as Reference Standard

AIM

Controlled attenuation parameter (CAP) enables the noninvasive diagnosis of liver steatosis. Magnetic resonance imaging proton density fat fraction (MRI-PDFF) is increasingly used over biopsy for the assessment of steatosis in patients at risk for metabolic dysfunction-associated steatotic liver disease (MASLD). We assessed the accuracy of CAP for liver steatosis defined as MRI-PDFF ≥ 5%.

METHODS

We performed a cross-sectional, diagnostic accuracy study. We prospectively recruited consecutive adult participants with type 2 diabetes and body mass index (BMI) ≥ 25 kg/m2, who underwent CAP and MRI-PDFF within two weeks.

RESULTS

We included 113 participants. The area under the receiver operating characteristic (AUROC) of CAP for MRI-PDFF ≥ 5% was 0.82 [95% confidence interval (CI) 0.74-0.89]. CAP thresholds for ruling-out (sensitivity > 90%) and ruling-in (specificity > 90%) liver steatosis were below 249 and over 328 dB/m respectively. The AUROC of CAP for the detection of MRI-PDFF ≥ 10% was 0.81 (0.73-0.88). CAP thresholds for ruling-out and ruling-in MRI-PDFF ≥ 10% were below 271 and over 345 dB/m respectively. CAP measurements with an interquartile range (IQR) < 30 dB/m improved the detection of higher steatosis grades.

CONCLUSION

CAP has acceptable accuracy for diagnosing MRI-PDFF defined steatosis. Values below 249 dB/m can be used to rule-out liver steatosis, while values over 328 dB/m can set the diagnosis. An IQR < 30 dB/m might improve the accuracy of CAP for higher steatosis grades.

CLINICAL TRIAL REGISTRATION

Not applicable.

Diffuse and focal liver fat: advanced imaging techniques and diagnostic insights

The fatty liver disease represents a complex, multifaceted challenge, requiring a multidisciplinary approach for effective management and research. This article uses conventional and advanced imaging techniques to explore the etiology, imaging patterns, and quantification methods of hepatic steatosis. Particular emphasis is placed on the challenges and advancements in the imaging diagnostics of fatty liver disease. Techniques such as ultrasound, CT, MRI, and elastography are indispensable for providing deep insights into the liver's fat content. These modalities not only distinguish between diffuse and focal steatosis but also help identify accompanying conditions, such as inflammation and fibrosis, which are critical for accurate diagnosis and management.

MAFLD in adults: non-invasive tests for diagnosis and monitoring of MAFLD

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the liver manifestation of a metabolic syndrome and is highly prevalent in the general population. There has been significant progress in non-invasive tests for MAFLD, from the diagnosis of fatty liver and monitoring of liver fat content in response to intervention, to evaluation of liver fibrosis and its change over time, and from risk stratification of patients within the context of clinical care pathways, to prognostication. Various non-invasive tests have also been developed to assess for fibrotic metabolic dysfunction-associated steatohepatitis, which has emerged as an important diagnostic goal, particularly in the context of clinical trials. Non-invasive tests can be used to diagnose clinically significant portal hypertension so that intervention can be administered to reduce the risk of decompensation. Furthermore, the use of risk stratification algorithms can identify at-risk patients for hepatocellular carcinoma surveillance. Beyond the liver, various tests that evaluate cardiovascular disease risk, assess sarcopenia and measure patient reported outcomes, can be utilized to improve the care of patients with MAFLD. This review provides an up-to-date overview of these non-invasive tests and the limitations of liver biopsy in the management of patients with MAFLD.

Quantitative Ultrasound and Ultrasound-Based Elastography for Chronic Liver Disease: Practical Guidance, From the AJR Special Series on Quantitative Imaging

Quantitative ultrasound (QUS) and ultrasound-based elastography techniques are emerging as non-invasive effective methods for assessing chronic liver disease. They are more accurate than B-mode imaging alone and more accessible than MRI as alternatives to liver biopsy. Early detection and monitoring of diffuse liver processes such as steatosis, inflammation, and fibrosis play an important role in guiding patient management. The most widely available and validated techniques are attenuation-based QUS techniques and shear-wave elastography techniques that measure shear-wave speed. Other techniques are supported by a growing body of evidence and are increasingly commercialized. This review explains general physical concepts of QUS and ultrasound-based elastography techniques for evaluating chronic liver disease. The first section describes QUS techniques relying on attenuation, backscatter, and speed of sound. The second section discusses ultrasound-based elastography techniques analyzing shear-wave speed, shear-wave dispersion, and shear-wave attenuation. With an emphasis on clinical implementation, each technique's diagnostic performance along with thresholds for various clinical applications are summarized, to provide guidance on analysis and reporting for radiologists. Measurement methods, advantages, and limitations are also discussed. The third section explores developments in quantitative contrast-enhanced and vascular ultrasound that are relevant to chronic liver disease evaluation.

Evaluation of MRI proton density fat fraction in hepatic steatosis: a systematic review and meta-analysis

BACKGROUND

Amidst the global rise of metabolic dysfunction-associated steatotic liver disease (MASLD), driven by increasing obesity rates, there is a pressing need for precise, non-invasive diagnostic tools. Our research aims to validate MRI Proton Density Fat Fraction (MRI-PDFF) utility, compared to liver biopsy, in grading hepatic steatosis in MASLD.

METHODS

A systematic search was conducted across Embase, PubMed/Medline, Scopus, and Web of Science until January 13, 2024, selecting studies that compare MRI-PDFF with liver biopsy for hepatic steatosis grading, defined as grades 0 (< 5% steatosis), 1 (5-33% steatosis), 2 (34-66% steatosis), and 3 (> 66% steatosis).

RESULTS

Twenty-two studies with 2844 patients were included. The analysis showed high accuracy of MRI-PDFF with AUCs of 0.97 (95% CI = 0.96-0.98) for grade 0 vs ≥ 1, 0.91 (95% CI = 0.88-0.93) for ≤ 1 vs ≥ 2, and 0.91 (95% CI = 0.88-0.93) for ≤ 2 vs 3, diagnostic odds ratio (DOR) from 98.74 (95% CI = 58.61-166.33) to 23.36 (95% CI = 13.76-39.68), sensitivity and specificity from 0.93 (95% CI = 0.88-0.96) to 0.76 (95% CI = 0.63-0.85) and 0.93 (95% CI = 0.88-0.96) to 0.89 (95% CI = 0.84-0.93), respectively. Likelihood ratio (LR) + ranged from 13.3 (95% CI = 7.4-24.0) to 7.2 (95% CI = 4.9-10.5), and LR - from 0.08 (95% CI = 0.05-0.13) to 0.27 (95% CI = 0.17-0.42). The proposed MRI-PDFF threshold of 5.7% for liver fat content emerges as a potential cut-off for the discrimination between grade 0 vs ≥ 1 (p = 0.075).

CONCLUSION

MRI-PDFF is a precise non-invasive technique for diagnosing and grading hepatic steatosis, warranting further studies to establish its diagnostic thresholds.

CLINICAL RELEVANCE STATEMENT

This study underscores the high diagnostic accuracy of MRI-PDFF for distinguishing between various grades of hepatic steatosis for early detection and management of MASLD, though further research is necessary for broader application.

KEY POINTS

MRI-PDFF offers precision in diagnosing and monitoring hepatic steatosis. The diagnostic accuracy of MRI-PDFF decreases as the grade of hepatic steatosis advances. A 5.7% MRI-PDFF threshold differentiates steatotic from non-steatotic livers.

Accuracy of controlled attenuation parameter for liver steatosis in patients at risk for metabolic dysfunction-associated steatotic liver disease using magnetic resonance imaging: a systematic review and meta-analysis

Background

The controlled attenuation parameter (CAP) enables the noninvasive assessment of liver steatosis. We performed a systematic review and meta-analysis to evaluate the diagnostic accuracy of CAP for identifying liver steatosis in patients at risk for metabolic dysfunction-associated steatotic liver disease (MASLD), using magnetic resonance imaging proton density fat fraction (MRI-PDFF) as the reference standard.

Methods

We searched Medline, Embase, Cochrane Library and gray literature sources up to March 2024. We defined MASLD as MRI-PDFF ≥5%. We also assessed the accuracy of CAP for identifying patients with MRI-PDFF ≥10%. We calculated pooled sensitivity and specificity estimates using hierarchical random-effects models. We assessed the risk of bias using the Quality Assessment of Diagnostic Accuracy Studies 2 tool, and the certainty in meta-analysis estimates using the Grading of Recommendations Assessment, Development and Evaluation framework.

Results

We included 8 studies with 1116 participants. The prevalence of MASLD ranged from 65.2-93.9%. Pooled sensitivity and specificity of CAP for MRI-PDFF ≥5% were 0.84 (95% confidence interval [CI] 0.79-0.88) and 0.77 (95%CI 0.68-0.84), respectively, with an area under the receiver operating characteristic curve (AUROC) of 0.88. The pooled sensitivity and specificity for MRI-PDFF ≥10% were 0.83 (95%CI 0.80-0.87) and 0.72 (95%CI 0.59-0.82), with an AUROC of 0.85. The certainty in our estimates was low to very low because of the high risk of bias, inconsistency and imprecision.

Conclusions

CAP has acceptable diagnostic accuracy for both MRI-PDFF ≥5% and MRI-PDFF ≥10%. Adequately powered and rigorously conducted diagnostic accuracy studies are warranted to establish the optimal CAP thresholds.

Development and validation of MRI-PDFF cutoffs for living liver donor eligibility assessment

Hepatic steatosis (HS) criteria for living donor liver transplantation (LDLT) donor eligibility should be based on large droplet fat as per Banff consensus recommendations. We aimed to establish magnetic resonance imaging proton density fat fraction cutoffs for HS assessment in potential LDLT donors. This retrospective study included consecutive potential LDLT donors who underwent MRI and liver biopsy between 2013 and 2023 at 2 tertiary institutions, each as development (n = 3062; 2015 men; median [IQR] age of 32 [25-38] y) and external validation (n = 472; 287 men; 35 [26-44] y) data sets. Proton density fat fraction (PDFF) was measured using dedicated MRI sequences. Histologic HS, defined as a large droplet fat fraction, was used as the reference standard. Dual PDFF cutoffs aimed at 95% sensitivity or 95% specificity, for diagnosing histologic HS of ≥10%, ≥20%, ≥30%, and ≥40%, were determined in the development data set using 10-fold cross-validation. The cutoffs were then validated in the external validation data set. The equation for estimating histologic HS from PDFF was also derived using linear regression. The PDFF cutoffs for histologic HS of ≥10%, ≥20%, ≥30%, and ≥40%, targeting 95% sensitivity, were 3.7%, 5.5%, 8.0%, and 10.0%, respectively. External validation demonstrated high sensitivities ≥97.9% with specificities ranging from 60.9% to 95.1%. The PDFF cutoffs targeting 95% specificity were 6.3%, 8.0%, 9.1%, and 10.1%, respectively. External validation rendered high specificities ranging from 88.5% to 95.3%, with sensitivities ranging from 76.6% to 100%. For diagnosing histologic HS ≥30%, which is the most prevalently used threshold for LDLT donor eligibility assessment, the PDFF cutoffs achieved sensitivities and specificities of over 90%. The equation of (Histologic HS = -2.95 + 1.93 × PDFF) was derived.

EASL-EASD-EASO Clinical Practice Guidelines on the Management of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously termed non-alcoholic fatty liver disease (NAFLD), is defined as steatotic liver disease (SLD) in the presence of one or more cardiometabolic risk factor(s) and the absence of harmful alcohol intake. The spectrum of MASLD includes steatosis, metabolic dysfunction-associated steatohepatitis (MASH, previously NASH), fibrosis, cirrhosis and MASH-related hepatocellular carcinoma (HCC). This joint EASL-EASD-EASO guideline provides an update on definitions, prevention, screening, diagnosis and treatment for MASLD. Case-finding strategies for MASLD with liver fibrosis, using non-invasive tests, should be applied in individuals with cardiometabolic risk factors, abnormal liver enzymes, and/or radiological signs of hepatic steatosis, particularly in the presence of type 2 diabetes (T2D) or obesity with additional metabolic risk factor(s). A stepwise approach using blood-based scores (such as FIB-4) and, sequentially, imaging techniques (such as transient elastography) is suitable to rule-out/in advanced fibrosis, which is predictive of liver-related outcomes. In adults with MASLD, lifestyle modification - including weight loss, dietary changes, physical exercise and discouraging alcohol consumption - as well as optimal management of comorbidities - including use of incretin-based therapies (e.g. semaglutide, tirzepatide) for T2D or obesity, if indicated - is advised. Bariatric surgery is also an option in individuals with MASLD and obesity. If locally approved and dependent on the label, adults with non-cirrhotic MASH and significant liver fibrosis (stage ≥2) should be considered for a MASH-targeted treatment with resmetirom, which demonstrated histological effectiveness on steatohepatitis and fibrosis with an acceptable safety and tolerability profile. No MASH-targeted pharmacotherapy can currently be recommended for the cirrhotic stage. Management of MASH-related cirrhosis includes adaptations of metabolic drugs, nutritional counselling, surveillance for portal hypertension and HCC, as well as liver transplantation in decompensated cirrhosis.

iATT liver fat quantification for steatosis grading by referring to MRI proton density fat fraction: a multicenter study

BACKGROUND

Several preliminary reports have suggested the utility of ultrasound attenuation coefficient measurements based on B-mode ultrasound, such as iATT, for diagnosing steatotic liver disease. Nonetheless, evidence supporting such utility is lacking. This prospective study aimed to investigate whether iATT is highly concordant with magnetic resonance imaging (MRI)-based proton density fat fraction (MRI-PDFF) and could well distinguish between steatosis grades.

METHODS

A cohort of 846 individuals underwent both iATT and MRI-PDFF assessments. Steatosis grade was defined as grade 0 with MRI-PDFF < 5.2%, grade 1 with 5.2% MRI-PDFF < 11.3%, grade 2 with 11.3% MRI-PDFF < 17.1%, and grade 3 with MRI-PDFF of 17.1%. The reproducibility of iATT and MRI-PDFF was evaluated using the Bland-Altman analysis and intraclass correlation coefficients, whereas the diagnostic performance of each steatosis grade was examined using receiver operating characteristic analysis.

RESULTS

The Bland-Altman analysis indicated excellent reproducibility with minimal fixed bias between iATT and MRI-PDFF. The area under the curve for distinguishing steatosis grades 1, 2, and 3 were 0.887, 0.882, and 0.867, respectively. A skin-to-capsula distance of ≥ 25 mm was identified as the only significant factor causing the discrepancy. No interaction between MRI-logPDFF and MRE-LSM on iATT values was observed.

CONCLUSIONS

Compared to MRI-PDFF, iATT showed excellent diagnostic accuracy in grading steatosis. iATT could be used as a diagnostic tool instead of MRI in clinical practice and trials. Trial registration This study was registered in the UMIN Clinical Trials Registry (UMIN000047411).

Surveillance of the liver in type 2 diabetes: important but unfeasible?

Fatty liver plays a pivotal role in the pathogenesis of the metabolic syndrome and type 2 diabetes. According to an updated classification, any individual with liver steatosis and one or more features of the metabolic syndrome, without excess alcohol consumption or other known causes of steatosis, has metabolic dysfunction-associated steatotic liver disease (MASLD). Up to 60-70% of all individuals with type 2 diabetes have MASLD. However, the prevalence of advanced liver fibrosis in type 2 diabetes remains uncertain, with reported estimates of 10-20% relying on imaging tests and likely overestimating the true prevalence. All stages of MASLD impact prognosis but fibrosis is the best predictor of all-cause and liver-related mortality risk. People with type 2 diabetes face a two- to threefold increase in the risk of liver-related death and hepatocellular carcinoma, with 1.3% progressing to severe liver disease over 7.7 years. Because reliable methods for detecting steatosis are lacking, MASLD mostly remains an incidental finding on imaging. Regardless, several medical societies advocate for universal screening of individuals with type 2 diabetes for advanced fibrosis. Proposed screening pathways involve annual calculation of the Fibrosis-4 (FIB-4) index, followed by a secondary test such as transient elastography (TE) for intermediate-to-high-risk individuals. However, owing to unsatisfactory biomarker specificity, these pathways are expected to channel approximately 40% of all individuals with type 2 diabetes to TE and 20% to tertiary care, with a false discovery rate of up to 80%, raising concerns about feasibility. There is thus an urgent need to develop more effective strategies for surveying the liver in type 2 diabetes. Nonetheless, weight loss through lifestyle changes, pharmacotherapy or bariatric surgery remains the cornerstone of management, proving highly effective not only for metabolic comorbidities but also for MASLD. Emerging evidence suggests that fibrosis biomarkers may serve as tools for risk-based targeting of weight-loss interventions and potentially for monitoring response to therapy.

Prevalence of at-risk MASH, MetALD and alcohol-associated steatotic liver disease in the general population

BACKGROUND

The prevalence of at-risk metabolic dysfunction-associated steatohepatitis (at-risk MASH) has not been systematically assessed.

AIM

To delineate the prevalence of at-risk MASH in a large population-based cohort.

METHODS

We conducted a cross-sectional analysis of 40,189 patients in the UK Biobank who underwent liver MRI. Hepatic steatosis was determined by proton density fat fraction (PDFF) ≥5%. Based on AASLD criteria, participants were classified as alcohol-associated steatotic liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), combined metabolic alcoholic liver disease (MetALD) and at-risk MASH.

RESULTS

Among 40,189 patients, 10,886 (27.0%) had a PDFF ≥5%, indicating SLD. Among patients with SLD, 1% had ALD, 89.0% had MASLD, 7.9% had MetALD and 2.2% had at-risk MASH. The at-risk MASH group, which included 0.6% of the general population, had the highest mean liver fat on MRI and the highest BMI. Serum biomarkers highlighted increased inflammation and metabolic changes in at-risk MASH. The prevalence of MASLD was significantly higher among men with a BMI ≥30 kg/m2. Non-obese women showed only a 12% risk of MASLD. Conversely, MetALD had similar prevalence in obese men and women and was absent in non-obese women.

CONCLUSIONS

MASLD is prevalent among patients with elevated PDFF on MRI. There are different sex- and BMI-specific prevalence of different steatotic liver disorders. At-risk MASH demonstrates the most severe metabolic and inflammatory profiles. This study provides novel estimates for the at-risk MASH population that will be eligible for treatment with pharmacologic therapy when approved by regulatory authorities.