Ultrasound Fatty Liver Indicator: A Simple Tool for Differentiating Steatosis From Nonalcoholic Steatohepatitis: Validity in the Average Obese Population

Accuracy of Non-Invasive Imaging Techniques for the Diagnosis of MASH in Patients With MASLD: A Systematic Review

BACKGROUND AND AIMS

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing public health problem. The secondary stage in MASLD is steatohepatitis (MASH), the co-existence of steatosis and inflammation, a leading cause of progression to fibrosis and mortality. MASH resolution alone improves survival. Currently, MASH diagnosis is via liver biopsy. This study sought to evaluate the accuracy of imaging-based tests for MASH diagnosis, which offer a non-invasive method of diagnosis.

METHODS

Eight academic literature databases were searched and references of previous systematic reviews and included papers were checked for additional papers. Liver biopsy was used for reference standard.

RESULTS

We report on 69 imaging-based studies. There were 31 studies on MRI, 27 on ultrasound, five on CT, 13 on transient elastography, eight on controlled attenuation parameter (CAP) and two on scintigraphy. The pathological definition of MASH was inconsistent, making it difficult to compare studies. 55/69 studies (79.71%) were deemed high-risk of bias as they had no preset thresholds and no validation. The two largest groups of imaging papers were on MRI and ultrasound. AUROCs were up to 0.93 for MRE, 0.90 for MRI, 1.0 for magnetic resonance spectroscopy (MRS) and 0.94 for ultrasound-based studies.

CONCLUSIONS

Our study found that the most promising imaging tools are MRI techniques or ultrasound-based scores and confirmed there is potential to utilise these for MASH diagnosis. However, many publications are single studies without independent prospective validation. Without this, there is no clear imaging tool or score currently available that is reliably tested to diagnose MASH.

Application of artificial intelligence techniques for non-alcoholic fatty liver disease diagnosis: A systematic review (2005-2023)

BACKGROUND AND OBJECTIVES

Non-alcoholic fatty liver disease (NAFLD) is a common liver disease with a rapidly growing incidence worldwide. For prognostication and therapeutic decisions, it is important to distinguish the pathological stages of NAFLD: steatosis, steatohepatitis, and liver fibrosis, which are definitively diagnosed on invasive biopsy. Non-invasive ultrasound (US) imaging, including US elastography technique, and clinical parameters can be used to diagnose and grade NAFLD and its complications. Artificial intelligence (AI) is increasingly being harnessed for developing NAFLD diagnostic models based on clinical, biomarker, or imaging data. In this work, we systemically reviewed the literature for AI-enabled NAFLD diagnostic models based on US (including elastography) and clinical (including serological) data.

METHODS

We performed a comprehensive search on Google Scholar, Scopus, and PubMed search engines for articles published between January 2005 and June 2023 related to AI models for NAFLD diagnosis based on US and/or clinical parameters using the following search terms: "non-alcoholic fatty liver disease", "non-alcoholic steatohepatitis", "deep learning", "machine learning", "artificial intelligence", "ultrasound imaging", "sonography", "clinical information".

RESULTS

We reviewed 64 published models that used either US (including elastography) or clinical data input to detect the presence of NAFLD, non-alcoholic steatohepatitis, and/or fibrosis, and in some cases, the severity of steatosis, inflammation, and/or fibrosis as well. The performances of the published models were summarized, and stratified by data input and algorithms used, which could be broadly divided into machine and deep learning approaches.

CONCLUSION

AI models based on US imaging and clinical data can reliably detect NAFLD and its complications, thereby reducing diagnostic costs and the need for invasive liver biopsy. The models offer advantages of efficiency, accuracy, and accessibility, and serve as virtual assistants for specialists to accelerate disease diagnosis and reduce treatment costs for patients and healthcare systems.

Discordance diagnosis between B-mode ultrasonography and MRI proton density fat fraction for fatty liver

We aimed to evaluate the frequency and causes of discordant results in fatty liver (FL) diagnosis between B-mode ultrasonography (B-USG) and magnetic resonance imaging proton density fat fraction (MRI-PDFF). We analyzed patients who underwent both B-USG and MRI-PDFF within a 6-month interval. We made a confusion matrix for FL diagnosis between B-USG and MRI-PDFF and identified four discordant groups as follows: (1) the "UFL-MnFL-wo" group [B-USG FL-MRI-PDFF no FL without chronic liver disease (CLD) or liver cirrhosis (LC)]; (2) the "UFL-MnFL-w" group (B-USG FL-MRI-PDFF no FL with CLD or LC); (3) the "UnFL-MFL-wo" group (B-USG no FL-MRI-PDFF FL without CLD or LC); and (4) the "UnFL-MFL-w" group (B-USG no FL-MRI-PDFF FL with CLD or LC). We compared the "UFL-MnFL-wo" group with the control group in terms of various parameters. We found 201 patients (201/1514, 13.3%) with discordant results for FL diagnosis between B-USG and MRI-PDFF. The "UFL-MnFL-wo" group accounted for the largest portion at 6.8% (103/1514), followed by the "UFL-MnFL-w" group (79/1514, 5.2%) and the "UnFL-MFL-w" group (16/1514, 1.1%). The mean and right PDFF values, body mass index, and abdominal wall thickness were significantly higher in the "UFL-MnFL-wo" group than in the control group (p ≤ 0.001). The frequency of discordant results in the diagnosis of FL between B-USG and MRI-PDFF could be identified. The causes of discordant results were that B-USG was fairly accurate in diagnosing FL disease and that accompanying CLD or LC hindered the evaluation of FL.

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.

Simultaneous imaging of ultrasonic relative backscatter and attenuation coefficients for quantitative liver steatosis assessment

Prevalence of liver disease is continuously increasing and nonalcoholic fatty liver disease (NAFLD) is the most common etiology. We present an approach to detect the progression of liver steatosis based on quantitative ultrasound (QUS) imaging. This study was performed on a group of 55 rats that were subjected to a control or methionine and choline deficient (MCD) diet known to induce NAFLD. Ultrasound (US) measurements were performed at 2 and 6 weeks. Thereafter, animals were humanely euthanized and livers excised for histological analysis. Relative backscatter and attenuation coefficients were simultaneously estimated from the US data and envelope signal-to-noise ratio was calculated to train a regression model for: (1) fat fraction percentage estimation and (2) performing classification according to Brunt's criteria in grades (0 <5%; 1, 5-33%; 2, >33-66%; 3, >66%) of liver steatosis. The trained regression model achieved an [Formula: see text] of 0.97 (p-value < 0.01) and a RMSE of 3.64. Moreover, the classification task reached an accuracy of 94.55%. Our results suggest that in vivo QUS is a promising noninvasive imaging modality for the early assessment of NAFLD.

Advances in the Diagnosis and Treatment of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease that affects approximately one-quarter of the global adult population, posing a significant threat to human health with wide-ranging social and economic implications. The main characteristic of NAFLD is considered that the excessive fat is accumulated and deposited in hepatocytes without excess alcohol intake or some other pathological causes. NAFLD is a progressive disease, ranging from steatosis to non-alcoholic steatohepatitis (NASH), cirrhosis, hepatocellular carcinoma, liver transplantation, and death. Therefore, NAFLD will probably emerge as the leading cause of end-stage liver disease in the coming decades. Unlike other highly prevalent diseases, NAFLD has received little attention from the global public health community. Liver biopsy is currently considered the gold standard for the diagnosis and staging of NAFLD because of the absence of noninvasive and specific biomarkers. Due to the complex pathophysiological mechanisms of NAFLD and the heterogeneity of the disease phenotype, no specific pharmacological therapies have been approved for NAFLD at present, although several drugs are in advanced stages of development. This review summarizes the current evidence on the pathogenesis, diagnosis and treatment of NAFLD.

Ultrasound Methods for the Assessment of Liver Steatosis: A Critical Appraisal

The prevalence of the non-alcoholic fatty liver disease has reached major proportions, being estimated to affect one-quarter of the global population. The reference techniques, which include liver biopsy and the magnetic resonance imaging proton density fat fraction, have objective practical and financial limitations to their routine use in the detection and quantification of liver steatosis. Therefore, there has been a rising necessity for the development of new inexpensive, widely applicable and reliable non-invasive diagnostic tools. The controlled attenuation parameter has been considered the point-of-care technique for the assessment of liver steatosis for a long period of time. Recently, many ultrasound (US) system manufacturers have developed proprietary software solutions for the quantification of liver steatosis. Some of these methods have already been extensively tested with very good performance results reported, while others are still under evaluation. This manuscript reviews the currently available US-based methods for diagnosing and grading liver steatosis, including their classification and performance results, with an appraisal of the importance of this armamentarium in daily clinical practice.

A reappraisal of the diagnostic performance of B-mode ultrasonography for mild liver steatosis

OBJECTIVES

Previous studies have shown that ultrasonography has high specificity (80-100%) but low sensitivity (50-70%) in diagnosing fatty liver, sensitivity is especially low for mild steatosis. In this study, we aimed to reappraise the diagnostic performance of B-mode ultrasonography for fatty liver disease.

METHODS

We performed a retrospective, multinational, multi-center, cross-sectional, observational study (six referral centers from three nations). We included 5056 participants who underwent both B-mode ultrasonography and magnetic resonance proton density fat fraction (MRI-PDFF) within a 6-month period. The diagnostic performance of B-mode ultrasonography was compared to MRI-PDFF as a reference standard for fatty liver diagnosis, using sensitivity, specificity, positive and negative predictive values, diagnostic accuracy, and area under the receiver operating characteristic curve (AUC).

RESULTS

B-mode ultrasonography showed a sensitivity of 83.4%, specificity of 81.0%, and AUC of 0.822 in diagnosing mild liver steatosis (6.5% ≤ MRI-PDFF ≤ 14%). The sensitivity, specificity, and AUC in diagnosing the presence of fatty liver disease (MRI-PDFF ≥ 6.5%) were 83.4%, 81.0%, and 0.822, respectively. Mean PDFF of B-mode ultrasonography-diagnosed non-fatty liver differed significantly from that of diagnosed mild liver steatosis (3.5 ± 2.8% vs. 8.5 ± 5.0%, p < 0.001). The inter-institutional variability of B-mode ultrasonography in diagnosing fatty liver was similar in diagnostic accuracy among the six centers (range, 82.8-88.6%, p = 0.416).

CONCLUSIONS

B-mode ultrasonography was an effective, objective method to detect mild liver steatosis using MRI-PDFF as comparison, regardless of the etiologies and comorbidities.

Clinical evaluation of grayscale and linear scale hepatorenal indices for fatty liver quantification: a prospective study of a native Chinese population

BACKGROUND AND AIMS

Hepato-renal index (HRI) has been investigated extensively in various clinical studies. New linear scale HRI (LS-HRI) is proposed as an alternative to conventional grayscale HRI (GS-HRI) that suffers from lack of a widely accepted cut-off value for differentiation of fatty from normal livers. To investigate the diagnostic performance of conventional GS-HRI and new LS-HRI for a relatively large Chinese population with NAFLD using a well-established ultrasonographic fatty liver indicator (US-FLI) as the reference standard for steatosis grades.

MATERIALS AND METHODS

A total of 106 patients with various stages of NAFLD were prospectively enrolled. All ultrasound images for these patients were first acquired by a highly experienced ultrasound doctor and their US-FLI scores then obtained by the same doctor. Both GS-HRI and LS-HRI values were measured off-line by two additional ultrasound doctors. Four steatosis grades were determined from US-FLI scores for steatosis detection and staging.

RESULTS

Inter-observer agreements for both GS-HRI and LS-HRI were excellent with the respective concordance correlation coefficient (CCC) of 0.900 for GS-HRI and 0.822 for LS-HRI. A linear correlation to US-FLI for LS-HRI (R = 0.74) was substantially superior to that for GS-HRI (R = 0.46). LS-HRI had a sensitivity of 85.9% and a specificity of 96.3% to differentiate steatosis from the normal liver (AUROC: 95.5%) while GS-HRI had a sensitivity of 85.9% and a specificity of 92.6% to distinguish steatosis from the normal liver (AUROC: 94.7%).

CONCLUSIONS

Both GS-HRI and LS-HRI measurements are reproducible between two ultrasonographic clinicians and are evidently effective for steatosis detection.

Diagnostic Modalities of Non-Alcoholic Fatty Liver Disease: From Biochemical Biomarkers to Multi-Omics Non-Invasive Approaches

Non-Alcoholic Fatty Liver Disease (NAFLD) is currently the most common cause of chronic liver disease worldwide, and its prevalence is increasing globally. NAFLD is a multifaceted disorder, and its spectrum includes steatosis to steatohepatitis, which may evolve to advanced fibrosis and cirrhosis. In addition, the presence of NAFLD is independently associated with a higher cardiometabolic risk and increased mortality rates. Considering that the vast majority of individuals with NAFLD are mainly asymptomatic, early diagnosis of non-alcoholic steatohepatitis (NASH) and accurate staging of fibrosis risk is crucial for better stratification, monitoring and targeted management of patients at risk. To date, liver biopsy remains the gold standard procedure for the diagnosis of NASH and staging of NAFLD. However, due to its invasive nature, research on non-invasive tests is rapidly increasing with significant advances having been achieved during the last decades in the diagnostic field. New promising non-invasive biomarkers and techniques have been developed, evaluated and assessed, including biochemical markers, imaging modalities and the most recent multi-omics approaches. Our article provides a comprehensive review of the currently available and emerging non-invasive diagnostic tools used in assessing NAFLD, also highlighting the importance of accurate and validated diagnostic tools.

Metabolic comorbidities and male sex influence steatosis in chronic hepatitis C after viral eradication by direct-acting antiviral therapy (DAAs): Evaluation by the controlled attenuation parameter (CAP)

BACKGROUND

Chronic hepatitis C (CHC) is associated with hepatic steatosis, related to both a direct viral action and metabolic features. Vice-versa data on hepatic steatosis after viral eradication by direct-acting antiviral agents (DAA) are undefined although the presence of metabolic alterations could strongly influence the occurrence of steatosis as in NAFLD. The controlled attenuation parameter (CAP) (FibroscanⓇ) allows the qualitative and quantitative evaluation of fatty liver.

AIM

to evaluate in patients with CHC whether hepatic steatosis diagnosed by CAP modifies after DAAs-induced sustained virologic response (SVR).

METHODS

Data were collected the day of DAAs therapy starting and six months after SVR. CAP ≥ 248 dB/m defined the presence of steatosis.

RESULTS

794 CHC SVR patients referring to 2 Italian Units were enrolled. Mean age was 64 ± 16 ys, 50% males, BMI 25.4 ± 4 kg/m², genotype type-1 in 73%, type-3 in 8%. Prevalence of hepatic steatosis at baseline was 32% by US and 46% by CAP. De novo steatosis developed in 125 (29%), resolution in 122 (30%). At multivariate analysis de novo steatosis was independently associated with male sex (OR 1.7, CI 95% 1.09-2.67; p = 0.02) and baseline BMI (for unit increase OR 1.19, CI 95%1.11-1.29; p < 0.001). Baseline BMI (for unit increase OR 0.47, CI 95% 0.25-0.89; p = 0.02) and triglycerides (for unit increase OR 0.93, CI 95% 0.87-0.99; p = 0.03) prevented steatosis resolution after therapy.

CONCLUSIONS

after SVR de novo steatosis and resolution of baseline steatosis are closely related to the presence of metabolic comorbidities.

Nonalcoholic fatty liver disease: use of diagnostic biomarkers and modalities in clinical practice

INTRODUCTION

The global burden of liver disease is increasing, and nonalcoholic fatty liver disease (NAFLD) is among the most common chronic liver diseases in Asia, Europe, North and South America. The field of noninvasive diagnostic and their role in staging, but also predicting outcome is evolving rapidly. There is a high-unmet need to stage patients with NAFLD and to identify the subset of patients at risk of progression to end-stage liver disease.

AREAS COVERED

The review covers all established diagnostic blood-based and imaging biomarkers to stage and grade NAFLD. Noninvasive surrogate scores are put into perspective of the available evidence and recommended use. The outlook includes genetics, combined algorithms, and artificial intelligence that will allow clinicians to guide and support the management in both early and later disease stages.

EXPERT OPINION

In the future, these diagnostics tests will help clinicians to establish patient care pathways and support the identification of relevant subgroups for monitoring and pharmacotherapy. In addition, researchers will be guided to better understand available scores and support the development of future prediction systems. These will likely include multiparametric aspects of the disease and machine learning algorithms will refine their use and integration with large datasets.

Association between the Severity of Nonalcoholic Fatty Liver Disease and the Risk of Coronary Artery Calcification

Background and Objectives: There are limited data on the association between severity of non-alcoholic fatty liver disease (NAFLD) and coronary artery calcification. This study investigated sonographic diagnosed NAFLD and coronary artery calcium score (CAC) as detected by cardiac multidetector computed tomography in general populations. Materials and Methods: A total of 545 patients were enrolled in this study. NAFLD was diagnosed by ultrasonography examination and CAC score were evaluated by cardiac multidetector computed tomography. The association between NAFLD and artery calcium score stage was determined by logistic regression analysis and Spearman correlation coefficient analysis. Results: Of all the participants, 437 (80.2%) had ultrasonography-diagnosed NAFLD and 242 (44%) had coronary artery calcification (CAC > 0). After adjustment for cardiovascular risk factors, the risk of developing coronary artery calcification was 1.36-fold greater in the patients with different severity of NAFLD compared to those without NAFLD (OR = 1.36, 95% CI = 1.07-1.77, p = 0.016). The highest OR for separate coronary artery calcification was 1.98 (OR = 1.98, 95% CI = 1.37-2.87, p < 0.001) in the left main artery, and the risk was still 1.71-fold greater after adjustments (OR = 1.71, 95% CI = 1.16-2.54, p = 0.007). Conclusions: This cross-sectional study demonstrated that the severity of NAFLD was associated with the presence of significant coronary artery calcification, especially in the left main coronary artery, suggesting increasing the cardiovascular risk.

Feasibility and efficiency of European guidelines for NAFLD assessment in patients with type 2 diabetes: A prospective study

AIM

We aimed to evaluate the feasibility and efficiency of a guidelines-compliant NAFLD assessment algorithm in patients with newly diagnosed type 2 diabetes (T2D).

METHODS

Consecutive patients aged < 75 newly diagnosed with T2D without coexisting liver disease or excessive alcohol consumption were enrolled. Patients were stratified based on liver enzymes, fatty liver index, ultrasound, fibrosis scores and liver stiffness measurement. Referral rates and positive predictive values (PPVs) for histological non-alcoholic steatohepatitis (NASH) and significant fibrosis were evaluated.

RESULTS

Of the 171 enrolled patients (age 59 ± 10.2 years, 42.1% females), 115 (67.3%) were referred to a hepatologist due to abnormal liver enzymes (n = 60) or steatosis plus indeterminate (n = 37) or high NAFLD fibrosis score (n = 18). Liver biopsy was proposed to 30 patients (17.5%), but only 14 accepted, resulting in 12 NASH, one with significant fibrosis. The PPV of hepatological referral was 12/76 (15.8%) for NASH and 1/76 (1.3%) for NASH with significant fibrosis. The PPV of liver biopsy referral was 12/14 (85.7%) for NASH and 1/14 (7.1%) for NASH with significant fibrosis.

CONCLUSIONS

By applying a guidelines-compliant algorithm, many patients with T2D were referred for hepatological assessment and liver biopsy. Further studies are necessary to refine non-invasive algorithms.

Gender Differences in the Relationships among Metabolic Syndrome and Various Obesity-Related Indices with Nonalcoholic Fatty Liver Disease in a Taiwanese Population

The incidence of nonalcoholic fatty liver disease (NAFLD) is increasing worldwide, and it is strongly associated with metabolic syndrome (MetS) and some obesity-related indices. However, few studies have investigated gender differences in these associations. The aim of this study was to investigate associations among MetS and various obesity-related indices with NAFLD, and also look at gender differences in these associations. We enrolled participants who completed a health survey in southern Taiwan. MetS was defined according to the Adult Treatment Panel III for Asians, and the following obesity-related indices were calculated: body mass index (BMI), waist-to-height ratio (WHtR), waist-hip ratio (WHR), lipid accumulation product (LAP), body roundness index (BRI), conicity index (CI), visceral adiposity index (VAI), body adiposity index (BAI), abdominal volume index (AVI), triglyceride-glucose (TyG) index, and hepatic steatosis index (HSI). NAFLD was diagnosed when hepatic steatosis was noted on a liver ultrasound. A total of 1969 (764 men and 1205 women) participants were enrolled. Multivariable analysis showed that both male and female participants with MetS, high BMI, high WHtR, high WHR, high LAP, high BRI, high CI, high VAI, high BAI, high AVI, high TyG index, and high HSI were significantly associated with NAFLD. In addition, the interactions between MetS and gender, WHR and gender, LAP and gender, and TyG index and gender on NAFLD were statistically significant. Among these obesity-related indices, HSI and LAP had the greatest area under the curve in both men and women. Furthermore, stepwise increases in the number of MetS components and the values of indices corresponding to the severity of NAFLD were noted. In conclusion, our results demonstrated significant relationships between MetS and obesity-related indices with NAFLD, and also stepwise increases in the number of MetS components and the values of indices with the severity of NAFLD. MetS, WHR, LAP, and TyG index were associated with NAFLD more obviously in women than in men.

Semi-Quantitative Ultrasonographic Evaluation of NAFLD

Nonalcoholic fatty liver disease (NAFLD) embraces histopathological entities ranging from the relatively benign simple steatosis to the progressive form nonalcoholic steatohepatitis (NASH), which is associated with fibrosis and an increased risk of progression to cirrhosis and hepatocellular carcinoma. NAFLD is the most common liver disease and is associated with extrahepatic comorbidities including a major cardiovascular disease burden. The non-invasive diagnosis of NAFLD and the identification of subjects at risk of progressive liver disease and cardio-metabolic complications are key in implementing personalized treatment schedules and follow-up strategies. In this review, we highlight the potential role of ultrasound semiquantitative scores for detecting and assessing steatosis severity, progression of NAFLD, and cardio-metabolic risk. Ultrasonographic scores of fatty liver severity act as sensors of cardio-metabolic health and may assist in selecting patients to submit to second-line non-invasive imaging techniques and/or liver biopsy.

Perspectives of nonalcoholic fatty liver disease research: a personal point of view

Rational government of patient fluxes from primary care to hepatology clinic is a priority of nonalcoholic fatty liver disease (NAFLD) research. Estimating pre-test probability of disease, risk of fibrosis progression, and exclusion of competing causes of liver disease must be addressed. Here we propose a novel taxonomic classification of NAFLD based on hepatic, pathogenic and systemic features of disease in the individual patient. The variable course of disease in any given patient remains a clinical enigma. Therefore, future studies will have to better characterize the role of genetic polymorphisms, family and personal history, diet, alcohol, physical activity and drugs as modifiers of the course of disease and clues to the early diagnosis of hepatocellular carcinoma. A better understanding of these, together with a taxonomic diagnosis, may prompt a more accurate personalization of care. For example, understanding the putative role of psycho-depression in NAFLD promises to revolutionize disease management in a proportion of cases. Similarly, sex differences in outcome and response to treatment are insufficiently characterized. More studies are awaited regarding those forms of NAFLD which occur secondary to endocrine derangements. The intersections between NAFLD and the lung must better be defined. These include the bi-directional associations of NAFLD and chronic obstructive pulmonary disease and sleep apnoea syndrome, as well as the totally unexplored chapter of NAFLD and coronavirus disease 2019 (COVID-19). Finally, the therapeutic roles of intermittent fasting and anticoagulation must be assessed. In conclusion, over the last 20 years, NAFLD has taught us a lot regarding the pathogenic importance of insulin resistance, the limitations of correcting this in the treatment of NAFLD, the root causes of diabetes and the metabolic syndrome, sex differences in disease and the role of nuclear receptors. However, the overwhelming COVID-19 pandemic is now expected to reset the priorities of public health.

Perspectives of nonalcoholic fatty liver disease research: a personal point of view

Rational government of patient fluxes from primary care to hepatology clinic is a priority of nonalcoholic fatty liver disease (NAFLD) research. Estimating pre-test probability of disease, risk of fibrosis progression, and exclusion of competing causes of liver disease must be addressed. Here we propose a novel taxonomic classification of NAFLD based on hepatic, pathogenic and systemic features of disease in the individual patient. The variable course of disease in any given patient remains a clinical enigma. Therefore, future studies will have to better characterize the role of genetic polymorphisms, family and personal history, diet, alcohol, physical activity and drugs as modifiers of the course of disease and clues to the early diagnosis of hepatocellular carcinoma. A better understanding of these, together with a taxonomic diagnosis, may prompt a more accurate personalization of care. For example, understanding the putative role of psycho-depression in NAFLD promises to revolutionize disease management in a proportion of cases. Similarly, sex differences in outcome and response to treatment are insufficiently characterized. More studies are awaited regarding those forms of NAFLD which occur secondary to endocrine derangements. The intersections between NAFLD and the lung must better be defined. These include the bi-directional associations of NAFLD and chronic obstructive pulmonary disease and sleep apnoea syndrome, as well as the totally unexplored chapter of NAFLD and coronavirus disease 2019 (COVID-19). Finally, the therapeutic roles of intermittent fasting and anticoagulation must be assessed. In conclusion, over the last 20 years, NAFLD has taught us a lot regarding the pathogenic importance of insulin resistance, the limitations of correcting this in the treatment of NAFLD, the root causes of diabetes and the metabolic syndrome, sex differences in disease and the role of nuclear receptors. However, the overwhelming COVID-19 pandemic is now expected to reset the priorities of public health.

Association between plasminogen activator inhibitor-1 in young adulthood and nonalcoholic fatty liver disease in midlife: CARDIA

BACKGROUND

Prior studies have demonstrated a cross-sectional association between elevated plasminogen activator inhibitor-1 (PAI-1) levels and nonalcoholic fatty liver disease (NAFLD). However, there are no prospective longitudinal assessments of the association between PAI-1 and NAFLD. We aimed to describe the association between PAI-1 levels in early adulthood with NAFLD in midlife.

METHODS

Among the 5115 participants in the coronary artery risk development in young adults (CARDIA) study, participants were randomly selected from a subset that was free of obesity, diabetes and hypertension at the 1992-1993 exam and attended the 2005-2006 exam (n = 996). A subset of participants (n = 896) also had CT liver fat measured (2010-2011). Participants with secondary causes of steatosis were excluded (n = 87). NAFLD was defined as liver attenuation ≤51 Hounsfield units. Logistic regression models assessed the association between PAI-1 and NAFLD.

RESULTS

Of 809 participants, 53% were female, 37% black with a mean age of 32 years. Median PAI-1 level at 1st assessment (1992-1993) was 23.4 ng/mL among participants with NAFLD vs 11.9 ng/mL among those without NAFLD (P < .0001). Median PAI-1 level at 2nd assessment (2005-2006) was 55.6 ng/mL among participants with NAFLD vs 19.5 ng/mL among those without NAFLD (P < .0001). Higher PAI-1 levels were independently associated with NAFLD (1st assessment adjusted OR [AOR] 2.16 per 1 standard deviation higher log(PAI-1) level (95% confidence interval [CI] 1.63-2.85); 2nd assessment AOR 2.71 (95% CI 2.03-3.61)).

CONCLUSIONS

Plasma PAI-1 levels in young adulthood were independently associated with NAFLD in midlife. Further studies may indicate whether PAI-1 plays a role in NAFLD pathophysiology.