Non-alcoholic fatty liver disease in adults 2021: A clinical practice guideline of the Italian Association for the Study of the Liver (AISF), the Italian Society of Diabetology (SID) and the Italian Society of Obesity (SIO)

Nonalcoholic fatty liver disease (NAFLD) is a common and emerging liver disease in adults, paralleling the epidemic of obesity and diabetes and leading to worrisome events (hepatocellular carcinoma and end-stage liver disease). In the past years, mounting evidence added insights about epidemiology, natural history, diagnosis and lifestyle-based or drug treatment of NAFLD. In this rapidly evolving scenario, members of the Associazione Italiana per lo Studio del Fegato, the Societa Italiana di Diabetologia and the Societa Italiana dell'Obesita reviewed current knowledge on NAFLD. The quality of the published evidence is graded, and practical recommendations are made following the rules and the methodology suggested in Italy by the Centro Nazionale per l'Eccellenza delle cure and Istituto Superiore di Sanita. Whenever possible, recommendations are placed within the context the Italian Healthcare system, with reference to specific experience and local diagnostic and management resources. Level of evidence Level of evidence of recommendations for each PICO question were reported according to available evidence. Abstract]))Appendix 2. Members of the guidelines panelCoordinator: Giulio Marchesini; AISF Members:

# Introduction
The present report is a summary of Clinical Practice Guidelines resulting from a cooperative work of the Associazione Italiana per lo Studio del Fegato (AISF), the Societa Italiana di Diabetologia (SID) and the Societa Italiana dell'Obesita (SIO). Current knowledge on the diagnosis and treatment of non-alcoholic fatty liver disease (NAFLD) is translated into relevant practical recommendations for management following the rules and the methodology suggested in Italy by the Centro Nazionale per l'Eccellenza delle cure (CNEC) and Istituto Superiore di Sanita (ISS). In this summary, we report the outline of disease burden and the risks associated with disease progression, followed by PICO questions and recommendations. The review of the literature at the basis of individual recommendations is uploaded as supplementary material.

## Burden of disease and risk factors
The natural history of nonalcoholic fatty liver disease (NAFLD) has been extensively investigated in the past 20 years [bib_ref] Global epidemiology of nonalcoholic fatty liver disease-Meta-analytic assessment of prevalence, incidence, and..., Younossi [/bib_ref]. Steatosis is the hallmark of NAFLD and has been identified as an independent risk factor for the full spectrum of liver damage including inflammation, 1 3 ballooning and fibrosis . The diagnosis of NAFLD requires the exclusion of both secondary causes and of alcohol consumption  30 g/day for men and  20 g/day for women . Recently, a consensus of experts proposed to overcome the current nomenclature "NAFLD" and adopt for a "positive" definition the acronym "Metabolic dysfunction-Associated Fatty Liver Disease (MAFLD)" using metabolic dysfunctions as diagnostic criteria independently of the presence of other causes of chronic liver disease . The mean prevalence of NAFLD worldwide is 24.1%, ranging from 13.5% in Africa to 31.8% in Middle East, with differences among studies also related to diagnostic methods, age, gender and ethnicity [bib_ref] Global epidemiology of nonalcoholic fatty liver disease-Meta-analytic assessment of prevalence, incidence, and..., Younossi [/bib_ref]. Italian studies indicate a prevalence of 22.5-27.0% in the general population [6-9], with a 2% prevalence of noninvasively assessed advanced fibrosis due to NAFLD . The prevalence increases in patients with metabolic comorbidities and the metabolic syndrome (MetS), defined by the presence of at least three metabolic alterations among elevated waist circumference ( 94 cm in males;  80 cm in females in Europids), elevated triglycerides ( 150 mg/dL), reduced HDL-C (< 40 mg/dL in males; < 50 mg/dL in females), elevated blood pressure (systolic pressure  130 mmHg and/or diastolic pressure  85 mm or antihypertensive drug treatment) and elevated fasting glucose ( 100 mg/dL antihyperglycemic treatment) . NAFLD is observed in 54-90% [9, 11] and 78.8% [12] of cases with obesity or with MetS, respectively. In the Dionysos study, the presence of steatosis was closely associated with obesity [13] and in the Dionysos and Nutrition Liver Study the risk of NAFLD was ninefold increased by the presence of BMI  30 kg/m 2 and sixfold by abdominal obesity (waist circumference  102 cm in males,  88 in females) , independently of altered liver enzymes. Raised liver enzymes, assumed as surrogate indexes of NAFLD, were reported in 21% of cases with obesity and did not increase systematically with obesity class . In a more recent analysis of 890 subjects of the community-based ABCD ("Alimentazione, Benessere Cardiovascolare e Diabete") study, Petta et al. reported a NAFLD prevalence of 48%, with a relative risk for obesity of 4.02 (95% confidence interval, 2.77-5.84) , but the various diagnostic tools and/or settings may provide slightly different results.
The prevalence of NAFLD is as high as 70-80% in patients with type 2 diabetes mellitus (T2DM) , who are also more likely to have nonalcoholic steatohepatitis (NASH) and cirrhosis, even in the presence of fairly normal serum aminotransferase levels . In Italian patients with diabetes NAFLD is reported in 59.0-73.2% , with about 13-18% of them experiencing advanced fibrosis . A bidirectional association exists between NAFLD and T2DM , worsening the course of both diseases; the presence of T2DM increases the risk of NAFLD progression to advanced fibrosis and cirrhosis, as well as also of incident hepatocellular carcinoma (HCC), liver-related hospital admissions and liver-related deaths , whereas the presence of NAFLD in T2DM is associated with a reduced probability of achieving good glycemic control, and exacerbates atherogenic dyslipidemia, further increasing the risk of chronic kidney disease and adverse CV outcomes , particularly in the presence of NASH-fibrosis .
The lifetime costs of all NASH patients in the United States in 2017 is estimated at $222.6 billion, and the cost of the advanced NASH population at $95.4 billion . Data from Italian local Health Units, based on administrative data and resources utilization, calculated an average direct cost for NAFLD/NASH progressively increasing from the nonadvanced stage, to advanced NAFLD disease, compensated cirrhosis, liver transplant, and hepatocellular carcinoma (HCC), also driven by comorbidities, up to over  65,000/ year . Considering the projections calculated by disease modelling for the next decades, the total costs is likely to become very challenging for the National Health system .

## Nafld mortality and morbidity
Patients with NAFLD have an increased overall mortality compared to matched control populations . According to a meta-analysis, overall mortality was reported to be 15.4 per 1000 person-years (range 11.7-20.3) for patients with NAFLD and 25.6 (range 6.3-103.8) for the cohort with NASH [bib_ref] Global epidemiology of nonalcoholic fatty liver disease-Meta-analytic assessment of prevalence, incidence, and..., Younossi [/bib_ref]. The presence of NASH [adjusted hazard ratio ( adj HR) 9.16], age ( adj HR 1.06), and the presence of T2DM ( adj HR 2.09) increased all-cause and liver-related mortality, after controlling for other variables. Liver-specific mortality was estimated as 0.8 (range 0.3-1.8) in NAFLD and 11.8 (range 7.1-19.5) in NASH [bib_ref] Global epidemiology of nonalcoholic fatty liver disease-Meta-analytic assessment of prevalence, incidence, and..., Younossi [/bib_ref]. Cardiovascular (CV) disease (CVD) remains the most common cause of death, independent of other metabolic comorbidities , driven by the atherogenic profile and widespread CV complications [32-34], independently of other known risk factors . Fibrosis stage is the strongest predictor for mortality from CVD and liver-related disease in a cohort of biopsy-proven NAFLD after up to 33 years of follow-up .
NAFLD is also associated with an approximate twofold increased risk of incident T2DM, ranging from a 35% to a 5.5-fold increase, independent of overweight/obesity and other common risk factors . The risk of incident T2DM appears to diminish over time following the improvement or resolution of NAFLD . Patients with NAFLD also have a nearly 40% increase in the long-term risk of incident chronic kidney disease , as well as other recognized associations with sleep apnea, osteoporosis, psoriasis and endocrinopathies [42].

## 3
The presence of NASH increases liver-related mortality , but the most important driver of mortality is fibrosis at histology, specifically, zone 3 sinusoidal fibrosis plus periportal fibrosis (stage 2), advanced fibrosis [bridging fibrosis (stage 3) or cirrhosis (stage 4)] [2, 45], associated with the multiple component of MetS . Patients with stage 4 fibrosis (cirrhosis) had a nearly tenfold risk of liverrelated complications [2], with liver-related events occurring in 8.9 per 100 person-years (95% CI 6.7-11.7). The reported annual incidence of hepatic decompensation was 3.3 and 15.6 per 100 person-years among patients with Child Pugh (CP)-A5 and CP-A6 cirrhosis, respectively [47].

## Hepatocellular carcinoma and extrahepatic cancers
NAFLD is the third-most common cause of HCC in the United States, after hepatitis C and alcohol-related disease, accounting for 14.1% of all cases . The cumulative incidence of NAFLD-associated HCC has been reported to range from 2.4 to 12.8% over a median follow-up period of 3.

## Lean nafld
The term 'lean' NAFLD refers to patients with a BMI within the ethnic-specific cut-off of normal weight, but frequently extended to the area of overweight (30 kg/m 2 in Caucasian and 27 kg/m 2 in Asian subjects). It is conceivable that 'lean' NAFLD comprises an heterogeneous NAFLD cohort associated with environmental and genetic factors, as well as differences in fat distribution and body composition [55], accounting for 5-26% of total NAFLD cases in the Asian population and 7-20% in the Western areas . A recent meta-analysis of 33 observational studies from 14 countries concluded for a global prevalence of NAFLD in lean individuals (BMI < 23 kg/m 2 for Asian subjects and BMI < 25 kg/m 2 for non-Asian subjects) of 9.7% (95% CI 7.7-11.8%), with an upward trend between 1988 and 2017 . Their rate of comorbidity is lower compared to obese patients, but higher compared to healthy controls . Data on histological severity are controversial; they can develop the full spectrum of liver disease associated with NASH [59] and similar adverse health outcomes when longitudinally examined [60, 61].

## Methods for guideline development
Following the needs of an updated guidance upon clinical management of the Non Alcoholic Fatty Liver Disease, the Scientific Societies whose members are primarily involved in its management (Italian Association for the Study of the Liver-AISF; Italian Society of Diabetology-SID; Italian Society of Obesity-SIO) commissioned to an experts panel the drafting of a new dedicated document to outline the updated clinical practice guidelines. The present document was made according to the rules dictated by the Italian Center for the Cure Excellence (Centro Nazionale per l'Eccellenza delle Cure-CNEC), an institution recently set up by the Italian National Institute of Health (Istituto Superiore di Sanita-ISS) to outline the methodologies needed to provide evidence-based clinical, diagnostic and therapeutic guidelines in Italy . According to these rules, a "multi-societary" and "multi-disciplinary" committee of experts was selected by the abovementioned Scientific Societies. The committee defined the objectives, the key issues and retrieved the relevant evidences by performing a systematic review of literature. Finally, the committee members (chosen on the basis of their specific expertise) identified the guidelines' key questions and developed them following the PICO format (Population, Intervention, Comparison, Outcomes) [63]. The most relevant questions were chosen by voting among the whole committee. The mean agreement among panel members on recommendations was 98.15%, as reported in supplementary table 1. For each PICO question, a systematic review of the literature was made on the most important scientific databases (Pubmed, Scopus, Embase) by performing both a free-text research and by a BOOLEAN research string formulated on purpose (see Online Appendix 1). The profiles of evidence were developed by applying the GRADE-Evidence to Decision (EtD) frameworks as per CNEC manual indications . In particular, all aspects regarding the questions, the assessment of evidence and the conclusions drawings were discussed between the panel members and voted to obtain a final decision. The GRADEpro GDT online tool was used to develop the questions and make the decisions 1 3
[65]. The quality of evidence was evaluated by applying the "Quality Assessment of Diagnostic Accuracy Studies version 2" (QUADAS-2) checklist for the diagnostic accuracy questions [66], the "revised tool for Risk of Bias in randomized trials" (RoB 2) [67] and the "Risk Of Bias in Non-randomized Studies-of Interventions" tool (ROBINS-I) [68] for randomized clinical trials and non-randomized studies where applicable.
The final draft was submitted for advice and revision to EpaC (Liver Patients' Association). Their comments were considered in the final version.

# Strength and limits
The present report is a summary of Clinical Practice Guidelines resulting from a cooperative multi-society work and by using rigorous methodology suggested in Italy by the Centro Nazionale per l'Eccellenza delle cure and Istituto Superiore di Sanita. Lack of awareness for NAFLD and obstacles to apply and implement guidelines could limit their utility.

## What is already known on this subject?
NAFLD is an emerging liver disease with a growing epidemiological and clinical burden.
National guidelines for the management of NAFLD patients are not still available.

## What this study adds?
The present document is the first effort to provide multisociety national guidelines on NAFLD aimed to a multidisciplinary and shared management of NAFLD patients.

## Pico questions and recommendations
(A) Assessment of disease severity PICO 1-In adult patients with NAFLD, should non-invasive scores, serum markers, liver stiffness, and imaging methods be used as replacement for liver biopsy for the diagnosis of NASH? depicts a two-step algorithm, based on FIB-4 or NAFLD fibrosis score as first step followed by LSM, 1 NAFLD is defined by ultrasound; in case of difficult access to ultrasound, clinicians can directly screen patients with features of metabolic syndrome by liver enzymes and noninvasive scores of fibrosis: 2 AST, ALT, GGT. Note that in patients referred to specialists (right side) follow-up will depend on disease severity/available therapeutic protocols; timing of follow-up in negative patients (left side) will depend on the presence of metabolic factors and comorbid conditions 1 3

## Recommendation
proposed for the assessment of fibrosis severity in patients with NAFLD. PICO 3-In adult patients with NAFLD, should non-invasive scores, liver stiffness and imaging methods be used as replacement for liver biopsy for predicting liver-related outcomes? (B) Weight loss and behavioral intervention for NAFLD

## Recommendations

## Pico 5-in adult patients with nafld, what is the efficacy of weight loss on histologically assessed liver damage and liver-related outcomes in comparison with no intervention?
Recommendation - All subjects with NAFLD, including lean (non-obese) NAFLD, should be involved in lifestyle programs aimed at healthy diet and habitual physical activity to a  7-10% weight loss target, repeatedly associated with improved histology, including fibrosis (B, 1)
- The dietary approach to NAFLD should favor adherence to the principles of the Mediterranean diet, including a reduced intake of refined and industrial sugars, associated with reduced hepatic fat content and decreased cardiovascular risk (B, 1) - Low-modest alcohol intake in noncirrhotic NAFLD patients should not be encouraged (C, 2) and total abstinence in NAFLD-cirrhosis is recommended (B, 1) - In patients with NAFLD, any types of physical activity, as well as reduced sedentariness, should be counseled, in order to reduce liver fat, independently of changes in body weight (B, 1) - Clinicians should recommend weight loss by intensive, structured lifestyle programs delivered under specialist control and/or pharmacotherapy and/or bariatric surgery in NAFLD subjects with obesity to reduce liver disease severity (A, 1)
References: [9, 124-175].

## (c) pharmacologic treatment for nafld
The epidemic of NAFLD and its complications and the discovery of different potential therapeutic targets for NASH treatment led to start an impressive number of clinical trials. International guidelines recommend that pharmacological therapy for NAFLD/NASH should be reserved to patients presenting an active disease and the presence of liver fibrosis  stage 2 [176, 177]. Moreover, the FDA (US Food and Drug Administration) and the EMA (European Medicines Agency) identified two endpoints for the conditional approval of drugs in patients with noncirrhotic NASH: (1) resolution of NASH without worsening of liver fibrosis, and (2) at least one stage improvement in liver fibrosis without worsening of NASH fibrosis . Consistently, most of the phase 2b and phase 3 trials enrolled patients with NASH plus fibrosis stage F2-F3. However, in spite of a large number of published or ongoing clinical trials, to date neither FDA, nor EMA or AIFA has approved any pharmacological treatment for patients with NASH.

## Pico 6-in adult patients with nafld, what is the efficacy of pharmacological treatment on histologically assessed liver damage and liver-related outcomes in comparison with no pharmacological intervention?

## Recommendation
- In patients with NASH pioglitazone may be used to improve NASH and fibrosis, although the drug is off-label and the risk/benefit balance related to pioglitazone side-effects should be discussed with each patient (B, 2) - In patients with NASH vitamin E may be used to improve NASH and fibrosis, even if risks and benefits should be discussed with each patient (B, 2) - In patients with NASH standard or high-dose ursodeoxycholic acid (UDCA) should not be used to treat NASH and fibrosis, because ineffective (B, 2) - In patients with NASH obeticholic acid may improve fibrosis without worsening of NASH, but its use is waiting for approval by regulatory agencies, based on additional safety and efficacy data (B, 2)

## Pico 7-in adult patients with nafld and type 2 diabetes mellitus, what is the efficacy of glucose-lowering treatment on histologically assessed liver damage and liver-related outcomes?
Recommendation - In T2DM patients with NAFLD/NASH, pioglitazone is specifically recommended to treat liver disease (B, 2) - In T2DM patients with NAFLD/NASH, metformin use is safe for the liver, but it is not specifically recommended to treat liver disease (B, 2) - In T2DM patients with NAFLD/NASH, DPP-4 inhibitors are safe for the liver, but their use is not specifically recommended to treat liver disease (C, 2) - In T2DM patients with NAFLD/NASH, GLP-1 receptor agonists are safe for the liver, but, despite preliminary evidence that may decrease liver damage, their use is not specifically approved to treat liver disease (B, 2) - In T2DM patients with NAFLD/NASH, SGLT-2 inhibitors are safe for the liver, but their use is not specifically recommended to treat liver disease (C, 2) References: [bib_ref] The Fatty Liver Index: a simple and accurate predictor of hepatic steatosis..., Bedogni [/bib_ref] [bib_ref] Performance and limitations of steatosis biomarkers in patients with nonalcoholic fatty liver..., Fedchuk [/bib_ref] [bib_ref] Diagnostic accuracy and reliability of ultrasonography for the detection of fatty liver:..., Hernaez [/bib_ref] [bib_ref] Magnetic resonance imaging proton density fat fraction associates with progression of fibrosis..., Ajmera [/bib_ref] [bib_ref] One hundred consecutive hepatic biopsies in the workup of living donors for..., Ryan [/bib_ref] [bib_ref] Radiologic evaluation of nonalcoholic fatty liver disease, Lee [/bib_ref] [bib_ref] Diagnostic value of MRI-PDFF for hepatic steatosis in patients with non-alcoholic fatty..., Gu [/bib_ref] [bib_ref] Diagnostic accuracy of controlled attenuation parameter (CAP) as a non-invasive test for..., Pu [/bib_ref] [bib_ref] Assessment of hepatic steatosis by controlled attenuation parameter using the M and..., Petroff [/bib_ref] [bib_ref] Optimal threshold of controlled attenuation parameter with MRI-PDFF as the gold standard..., Caussy [/bib_ref] [bib_ref] Can the same controlled attenuation parameter cut-offs be used for M and..., Chan [/bib_ref] [bib_ref] Individual patient data meta-analysis of controlled attenuation parameter (CAP) technology for assessing..., Karlas [/bib_ref].

# Conclusion
In the past few years, NAFLD emerged as a common liver disease in adults frequently associated with metabolic alterations, and as a leading cause of HCC and liver decompensation, finally impacting resource utilization and costs of the Healthcare systems. Also in Italy, the cost associated with NAFLD for the National Health System is rapidly increasing . The growing interest for NAFLD lead to the development of new diagnostic tools and algorithms to identify and refer patients at high risk of liver damage to liver specialists for assessment and treatment. The implementation of lifestyle programs aimed at weight loss and ongoing clinical trials with drugs targeting pathogenic pathways responsible for necroinflammation and fibrosis open new scenario in the management of NAFLD patients [bib_ref] Management of non-alcoholic fatty liver disease, Petroni [/bib_ref]. The present guidelines are conceived to promote a fruitful collaboration between different specialties, in a multidisciplinary approach aimed at disseminating and improving treatment within the healthcare professionals. Given the impressive amount of research and the extraordinary advances of the past few years, the several attempts to define new treatment strategies and the large number of trials supported by pharmaceutical companies, the proposed recommendations should be considered provisional and the Writing Commission recommends systematic update of Guidelines at regular intervals.
Finally, given its epidemiological, clinical and economic burden, NAFLD should be classified as a definite liver disease by the Health Care Italian System, independently of the presence of other metabolic comorbidities, with appropriate regulations in terms of diagnosis and treatment.

## Appendix 1: bibliographic research strategy
- identification of information needs: scientific evidence concerning the pathogenesis, diagnosis and treatment of non-alcoholic steatosis. - planning of the research strategy: for each topic assigned, the researchers personally searched for the bibliographic sources, using digital or paper resources if necessary. - choice of tools for information retrieval: the identified articles were obtained from the online library of the Institution to which the member of the experts' panel belongs. If not available online, the article was searched among the paper volumes of institutional libraries or was obtained through a direct request to the author of the publication. - identification of adequate sources of information: only articles from journals indexed on scientific search engines (PubMed, Embase, Scopus) were included, excluding non-scientific repertoires and newspapers articles, case reports, conference abstracts not published in-extenso. The keywords used for the research were the following:
1 Research topic: classification, diagnosis and prognosis of non-alcoholic steatosis.
Free-text research keywords: liver steatosis, nonalcoholic fatty liver, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, classification, diagnosis, prognosis. 
[fig] : In patients with NAFLD, non-invasive tools might acceptably rule out fibrosis progression (C, 2) In patients with NAFLD, noninvasive tools might acceptably predict the risk of occurrence of overall and liverrelated events and mortality (C, 2)References: [35, 102-112].PICO 4-In adult patients with NAFLD, should genetic testing be used as an add-on after usual testing in predicting the severity of histologically assessed liver damage and liver-related outcomes?Recommendations Clinicians in referral centers might consider the genetic risk profile for stratification of individual NAFLD-HCC risk, but the effectiveness of such strategy requires larger prospective studies (C, 2) We suggest that genetic risk variants be evaluated in clinical studies for stratification of disease risk progression and sub-phenotyping of NAFLD ( [/fig]
[fig] PICO 9 -PICO 10 -: In adult patients with NASH and morbid obesity, candidate for liver transplantation, what is the efficacy of bariatric surgery on preand post-transplant outcomes in comparison with no bariatric surgery? In the adult population are non-invasive scores and imaging methods useful for the diagnosis of NAFLD? Recommendations  Non-invasive scores (Fatty Liver Index-FLI) may be useful in population studies for the diagnosis of steatosis (A, 1)  Ultrasonography (US) is the first-line diagnostic procedure for detecting NAFLD, as it has high accuracy for moderate-severe steatosis and also provides additional diagnostic information (A, 1)  1 H-Magnetic Resonance Spectroscopy (MRS) is the reference standard for a quantitative estimation of liver fat. This technique should be preferred in clinical trials, but it is not recommended in clinical practice because expensive and not largely available (A, 2)  Controlled Attenuation Parameter (CAP) is an alternative tool for non-invasive assessment and follow-up of steatosis but more data are needed to definitively define its role (B, 2) [/fig]
[fig] PICO 11 -: In adult population with metabolic risk factors are non-invasive scores, liver stiffness and imaging methods useful for the diagnosis of advanced fibrosis? Recommendations  In adult individuals with one or more features of the metabolic syndrome, a combination of non-invasive fibrosis markers may help improve referral of patients with advanced liver fibrosis from primary care to specialist setting, also reducing the cost of management (B, 2) References: [16, 47, 276-282]. [/fig]
 [bib_ref] The diagnosis and management of non-alcoholic fatty liver disease: practice Guideline by..., Chalasani [/bib_ref] [bib_ref] Obesity and its effect on survival in patients undergoing orthotopic liver transplantation..., Nair [/bib_ref] [bib_ref] Recommendations for management and treatment of nonalcoholic steatohepatitis, Ratziu [/bib_ref] [bib_ref] The impact of type 2 diabetes and obesity on the long-term outcomes..., Younossi [/bib_ref] [bib_ref] Increased perioperative mortality following bariatric surgery among patients with cirrhosis, Mosko [/bib_ref] [bib_ref] Laparoscopic sleeve gastrectomy is safe and efficacious for pretransplant candidates, Lin [/bib_ref] [bib_ref] Laparoscopic bariatric surgery improves candidacy in morbidly obese patients awaiting transplantation, Takata [/bib_ref] [bib_ref] The role of bariatric surgery in abdominal organ transplantationthe next big challenge?, Dziodzio [/bib_ref] [bib_ref] Combined liver transplantation and gastric sleeve resection for patients with medically complicated..., Heimbach [/bib_ref]