AGA Clinical Practice Update on the Role of Noninvasive Biomarkers in the Evaluation and Management of Nonalcoholic Fatty Liver Disease: Expert Review

DescriptionThe purpose of this American Gastroenterological Association (AGA) Clinical Practice Update Expert Review is to provide clinicians with guidance on the use of noninvasive tests (NITs) in the evaluation and management of patients with nonalcoholic fatty liver disease (NAFLD). NAFLD affects nearly 30% of the global population and is a growing cause of end-stage liver disease and liver-related health care resource utilization. However, only a minority of all patients with NAFLD experience a liver-related outcome. It is therefore critically important for clinicians to assess prognosis and identify those with increased risk of disease progression and negative clinical outcomes at the time of initial assessment. It is equally important to assess disease trajectory over time, particularly in response to currently available therapeutic approaches. The reference standard for assessment of prognosis and disease monitoring is histologic examination of liver biopsy specimens. There are, however, many limitations of liver biopsies and their reading that have limited their use in routine practice. The utilization of NITs facilitates risk stratification of patients and longitudinal assessment of disease progression for patients with NAFLD. This clinical update provides best practice advice based on a review of the literature on the utilization of NITs in the management of NAFLD for clinicians. Accordingly, a combination of available evidence and consensus-based expert opinion, without formal rating of the strength and quality of the evidence, was used to develop these best practice advice statements.MethodsThis Expert Review was commissioned and approved by the AGA Institute Clinical Practice Updates Committee and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership and underwent internal peer review by the Clinical Practice Updates Committee and external peer review through standard procedures of Gastroenterology. These best practice advice statements were drawn from a review of the published literature and from expert opinion. Because systematic reviews were not performed, these best practice advice statements do not carry formal ratings of the quality of evidence or strength of the presented considerations.Best Practice Advice StatementsBest Practice Advice 1NITs can be used for risk stratification in the diagnostic evaluation of patients with NAFLD.Best Practice Advice 2A Fibrosis 4 Index score <1.3 is associated with strong negative predictive value for advanced hepatic fibrosis and may be useful for exclusion of advanced hepatic fibrosis in patients with NAFLD.Best Practice Advice 3A combination of 2 or more NITs combining serum biomarkers and/or imaging-based biomarkers is preferred for staging and risk stratification of patients with NAFLD whose Fibrosis 4 Index score is >1.3.Best Practice Advice 4Use of NITs in accordance with manufacturer’s specifications (eg, not in patients with ascites or pacemakers) can minimize risk of discordant results and adverse events.Best Practice Advice 5NITs should be interpreted with context and consideration of pertinent clinical data (eg, physical examination, biochemical, radiographic, and endoscopic) to optimize positive predictive value in the identification of patients with advanced fibrosis.Best Practice Advice 6Liver biopsy should be considered for patients with NIT results that are indeterminate or discordant; conflict with other clinical, laboratory, or radiologic findings; or when alternative etiologies for liver disease are suspected.Best Practice Advice 7Serial longitudinal monitoring using NITs for assessment of disease progression or regression may inform clinical management (ie, response to lifestyle modification or therapeutic intervention).Best Practice Advice 8Patients with NAFLD and NITs results suggestive of advanced fibrosis (F3) or cirrhosis (F4) should be considered for surveillance of liver complications (eg, hepatocellular carcinoma screening and variceal screening per Baveno criteria). Patients with NAFLD and NITs suggestive of advanced hepatic fibrosis (F3) or (F4), should be monitored with serial liver stiffness measurement; vibration controlled transient elastography; or magnetic resonance elastography, given its correlation with clinically significant portal hypertension and clinical decompensation. The purpose of this American Gastroenterological Association (AGA) Clinical Practice Update Expert Review is to provide clinicians with guidance on the use of noninvasive tests (NITs) in the evaluation and management of patients with nonalcoholic fatty liver disease (NAFLD). NAFLD affects nearly 30% of the global population and is a growing cause of end-stage liver disease and liver-related health care resource utilization. However, only a minority of all patients with NAFLD experience a liver-related outcome. It is therefore critically important for clinicians to assess prognosis and identify those with increased risk of disease progression and negative clinical outcomes at the time of initial assessment. It is equally important to assess disease trajectory over time, particularly in response to currently available therapeutic approaches. The reference standard for assessment of prognosis and disease monitoring is histologic examination of liver biopsy specimens. There are, however, many limitations of liver biopsies and their reading that have limited their use in routine practice. The utilization of NITs facilitates risk stratification of patients and longitudinal assessment of disease progression for patients with NAFLD. This clinical update provides best practice advice based on a review of the literature on the utilization of NITs in the management of NAFLD for clinicians. Accordingly, a combination of available evidence and consensus-based expert opinion, without formal rating of the strength and quality of the evidence, was used to develop these best practice advice statements. This Expert Review was commissioned and approved by the AGA Institute Clinical Practice Updates Committee and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership and underwent internal peer review by the Clinical Practice Updates Committee and external peer review through standard procedures of Gastroenterology. These best practice advice statements were drawn from a review of the published literature and from expert opinion. Because systematic reviews were not performed, these best practice advice statements do not carry formal ratings of the quality of evidence or strength of the presented considerations. Best Practice Advice Statements NITs can be used for risk stratification in the diagnostic evaluation of patients with NAFLD. A Fibrosis 4 Index score <1.3 is associated with strong negative predictive value for advanced hepatic fibrosis and may be useful for exclusion of advanced hepatic fibrosis in patients with NAFLD. A combination of 2 or more NITs combining serum biomarkers and/or imaging-based biomarkers is preferred for staging and risk stratification of patients with NAFLD whose Fibrosis 4 Index score is >1.3. Use of NITs in accordance with manufacturer’s specifications (eg, not in patients with ascites or pacemakers) can minimize risk of discordant results and adverse events. NITs should be interpreted with context and consideration of pertinent clinical data (eg, physical examination, biochemical, radiographic, and endoscopic) to optimize positive predictive value in the identification of patients with advanced fibrosis. Liver biopsy should be considered for patients with NIT results that are indeterminate or discordant; conflict with other clinical, laboratory, or radiologic findings; or when alternative etiologies for liver disease are suspected. Serial longitudinal monitoring using NITs for assessment of disease progression or regression may inform clinical management (ie, response to lifestyle modification or therapeutic intervention). Patients with NAFLD and NITs results suggestive of advanced fibrosis (F3) or cirrhosis (F4) should be considered for surveillance of liver complications (eg, hepatocellular carcinoma screening and variceal screening per Baveno criteria). Patients with NAFLD and NITs suggestive of advanced hepatic fibrosis (F3) or (F4), should be monitored with serial liver stiffness measurement; vibration controlled transient elastography; or magnetic resonance elastography, given its correlation with clinically significant portal hypertension and clinical decompensation. Nonalcoholic fatty liver disease (NAFLD) is an emerging global public health crisis. It affects approximately 30% of the worldwide population.1Younossi Z.M. Golabi P. Paik J.M. et al.The global epidemiology of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH): a systematic review.Hepatology. 2023; 77: 1335-1347Crossref PubMed Scopus (107) Google Scholar As a metabolic disease representing the hepatic manifestation of a systemic metabolic disorder, NAFLD is associated with significant morbidity and mortality, as well as substantial health care resource utilization.2Allen A.M. Lazarus J.V. Younossi Z.M. Healthcare and socioeconomic costs of NAFLD: a global framework to navigate the uncertainties.J Hepatol. 2023; 79: 209-217Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar,3Younossi Z.M. Non-alcoholic fatty liver disease - a global public health perspective.J Hepatol. 2019; 70: 531-544Abstract Full Text Full Text PDF PubMed Scopus (1161) Google Scholar The traditional approach to defining disease severity in patients with NAFLD has been to perform a liver biopsy for histologic grading of necroinflammation and staging of hepatic fibrosis—2 key features of disease severity. Disease activity refers to the biological processes leading to hepatic injury and inflammation, whereas fibrosis stage refers to the amount of scarring and thus proximity to cirrhosis. Fibrosis stage is the strongest predictor of future outcomes and thus provides the greatest prognostic information. Natural history studies have found that assessment of fibrosis, specifically cirrhosis, serves as a meaningful surrogate for liver-related outcomes, such as hepatocellular carcinoma (HCC), liver decompensation (eg, variceal hemorrhage, ascites, and hepatic encephalopathy), liver transplantation, and death.3Younossi Z.M. Non-alcoholic fatty liver disease - a global public health perspective.J Hepatol. 2019; 70: 531-544Abstract Full Text Full Text PDF PubMed Scopus (1161) Google Scholar,4Angulo P. Kleiner D.E. Dam-Larsen S. et al.Liver fibrosis, but no other histologic features, is associated with long-term outcomes of patients with nonalcoholic fatty liver disease.Gastroenterology. 2015; 149: 389-397.e10Abstract Full Text Full Text PDF PubMed Scopus (1921) Google Scholar Liver biopsies, however, are invasive; variable in sampling5Ratziu V. Charlotte F. Heurtier A. et al.Sampling variability of liver biopsy in nonalcoholic fatty liver disease.Gastroenterology. 2005; 128: 1898-1906Abstract Full Text Full Text PDF PubMed Scopus (1591) Google Scholar; subject to intra- and interobserver variability; and, rarely, may be associated with severe and/or fatal procedural complications. It is thus impractical to use biopsy-based risk stratification for a prevalent and chronic disease such as NAFLD. Noninvasive tests (NITs) have emerged as validated tools to address the problem of early risk stratification in NAFLD. Guidance for clinicians on the use of NITs in the care of patients with NAFLD is limited. We reviewed the use of NITs as a noninvasive surrogate approach to risk stratification of advanced fibrosis (AF) in the longitudinal care of patients with NAFLD to predict liver-related outcomes and guide responses to therapies. NITs can be subcategorized into serum-based and imaging-based biomarkers. Multiple noninvasive models using biochemical serum and clinical measurements have been proposed to detect liver fibrosis. The focus of this review will be on readily available, point-of-care, cost-effective testing strategies to risk stratify patients with NAFLD for AF. This review was designed to provide best practice advice (BPA) and guidance on several key clinical issues pertaining to NAFLD management using NITs. We have developed BPA statements to address 8 key clinical issues. This Expert Review was commissioned and approved by the American Gastroenterological Association (AGA) Institute Clinical Practice Updates Committee and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership and underwent internal peer review by the Clinical Practice Updates Committee and external peer review through standard procedures of the journal Gastroenterology. These BPA statements represent the current literature in studied populations. However, risk stratification should be undertaken only upon confirmation of diagnosis of NAFLD, exclusion of competing diagnoses, and evaluation of presenting signs and symptoms in accordance with good clinical practice. Furthermore, the final approach used for a given patient must take into consideration the unique clinical context for that patient and having discussed the “pros and cons” of alternative approaches. Among patients with NAFLD, those with nonalcoholic steatohepatitis (NASH) are at risk of fibrosis progression. Most experts believe that patients with NAFLD should be monitored for development of chronic liver injury (ie, NASH and hepatic fibrosis). Within the context of a gastroenterology practice, surveillance strategies for monitoring liver-related outcomes are implemented upon the knowledge of the presence of advanced hepatic fibrosis or cirrhosis. A patient’s access and engagement with the health care system, ability to follow lifestyle recommendations, and effective extrahepatic disease management may also improve clinical outcomes in patients with NAFLD. A key predictor for liver-related outcomes is AF, defined as presence of stage 3 (bridging fibrosis) or 4 (cirrhosis) on liver biopsy.6Sanyal A.J. Van Natta M.L. Clark J. et al.Prospective study of outcomes in adults with nonalcoholic fatty liver disease.N Engl J Med. 2021; 385: 1559-1569Crossref PubMed Scopus (282) Google Scholar Because fibrosis stage is not synchronized across the liver, stages 3–4 represent a continuum of fibrosis. Initial NITs were developed and applied to patients with viral hepatitis,7Sterling R.K. Lissen E. Clumeck N. et al.Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection.Hepatology. 2006; 43: 1317-1325Crossref PubMed Scopus (2975) Google Scholar but have subsequently been validated in other chronic liver diseases, specifically NAFLD.8McPherson S. Stewart S.F. Henderson E. et al.Simple non-invasive fibrosis scoring systems can reliably exclude advanced fibrosis in patients with non-alcoholic fatty liver disease.Gut. 2010; 59: 1265-1269Crossref PubMed Scopus (634) Google Scholar Several have been developed (eg, Fibrosis 4 Index [FIB-4] score, NAFLD fibrosis score [NAFLD-FS], and aspartate aminotransferase to platelet ratio index [APRI]; however, FIB-4 score is the most validated. FIB-4 score is calculated using a simple algorithm based on age, alanine aminotransferase, aspartate aminotransferase, and platelet count7Sterling R.K. Lissen E. Clumeck N. et al.Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection.Hepatology. 2006; 43: 1317-1325Crossref PubMed Scopus (2975) Google Scholar and outperforms other calculations in its ability to identify patients with a low probability of AF. High values of FIB-4 and other NITs have also been associated with all-cause and liver-related outcomes in population-based studies.9Unalp-Arida A. Ruhl C.E. Liver fibrosis scores predict liver disease mortality in the United States population.Hepatology. 2017; 66: 84-95Crossref PubMed Scopus (139) Google Scholar Although FIB-4 score does not outperform other proprietary fibrosis biomarkers (eg, FibroTest/FibroSure [eviCore Healthcare], FIBROSpect NASH [Prometheus Laboratories], Hepamet Fibrosis Score, a Pro-C3 based score [ADAPT], FibroMeter [ARUP Laboratories], and Hepascore), FIB-4 is recommended as a first-line assessment for practitioners based on its simplicity and low cost.10Kanwal F. Shubrook J.H. Adams L.A. et al.Clinical care pathway for the risk stratification and management of patients with nonalcoholic fatty liver disease.Gastroenterology. 2021; 161: 1657-1669Abstract Full Text Full Text PDF PubMed Scopus (151) Google Scholar, 11Cusi K. Isaacs S. Barb D. et al.American Association of Clinical Endocrinology Clinical Practice Guideline for the Diagnosis and Management of Nonalcoholic Fatty Liver Disease in Primary Care and Endocrinology Clinical Settings: Co-Sponsored by the American Association for the Study of Liver Diseases (AASLD).Endocr Pract. 2022; 28: 528-562Abstract Full Text Full Text PDF PubMed Scopus (175) Google Scholar, 12Rinella M.E. Neuschwander-Tetri B.A. Siddiqui M.S. et al.AASLD practice guidance on the clinical assessment and management of nonalcoholic fatty liver disease.Hepatology. 2023; 77: 1797-1835Crossref PubMed Scopus (101) Google Scholar The Enhanced Liver Fibrosis (ELF; Siemens Healthineers USA) test, a proprietary blood test consisting of 3 elements involved in matrix turnover, and NIS2+™ (property of GENFIT; Loos, France), as an optimization of NIS4® (property of GENFIT; Loos, France) technology, are validated blood-based serum biomarkers for detection of advanced hepatic fibrosis and “at-risk” NASH with F2 or higher, respectively. An ELF score ≥9.8 reliably identifies patients with NAFLD at increased risk of progression to cirrhosis and liver-related clinical events.13Miele L. De Michele T. Marrone G. et al.Enhanced Liver Fibrosis test as a reliable tool for assessing fibrosis in nonalcoholic fatty liver disease in a clinical setting.Int J Biol Markers. 2017; 32: e397-e402Crossref PubMed Scopus (24) Google Scholar,14Guha I.N. Parkes J. Roderick P. et al.Noninvasive markers of fibrosis in nonalcoholic fatty liver disease: validating the European Liver Fibrosis Panel and exploring simple markers.Hepatology. 2008; 47: 455-460Crossref PubMed Scopus (609) Google Scholar Such serum-based fibrosis tests may be good options as secondary risk assessments when elastography is not available. Imaging-based biomarkers, such as vibration controlled transient elastography (VCTE), shear wave elastography (SWE), and magnetic resonance elastography (MRE), are used most frequently and have been validated. Ultrasound-based 3-dimensional elastography (Velacur) and iron-corrected T1 magnetic resonance imaging, although used less frequently, are emerging technologies. Currently, there is no minimum cutoff established for diagnostic accuracy for AF using NITs. Using liver histology as the reference standard, a meta-analysis of 10 studies evaluated the performance of serum based and imaging NITs in NAFLD.15Xiao G. Zhu S. Xiao X. et al.Comparison of laboratory tests, ultrasound, or magnetic resonance elastography to detect fibrosis in patients with nonalcoholic fatty liver disease: a meta-analysis.Hepatology. 2017; 66: 1486-1501Crossref PubMed Scopus (538) Google Scholar The performance of FIB-4 for absence of AF with a cutoff value in the 1.24–1.45 range in 2759 patients demonstrated a mean sensitivity of 77.8% (range, 63.0%–90.0%), specificity of 71.2% (range, 55.5%–88.0%), positive predictive value (PPV) of 40.3% (range, 24.0%–50.6%), and negative predictive value (NPV) of 92.7% (range, 88.0%–98.0%). An FIB-4 score threshold of <1.3 was otherwise adapted from several studies as being an ideal threshold for clinical practice. NAFLD-FS performance for AF using a cutoff of –1.455 in 10 studies with 3057 patients had a sensitivity of 72.9% (range, 22.7%–96.0%), specificity of 73.8% (range, 42.9%–100%), PPV of 50.4% (range, 24.0%–100%), and NPV of 91.8% (range, 81.3%–98.1%).15Xiao G. Zhu S. Xiao X. et al.Comparison of laboratory tests, ultrasound, or magnetic resonance elastography to detect fibrosis in patients with nonalcoholic fatty liver disease: a meta-analysis.Hepatology. 2017; 66: 1486-1501Crossref PubMed Scopus (538) Google Scholar An APRI cutoff of 1.00 for AF in 1101 patients had a sensitivity of 43.2% (range, 27.0%–67.0%), specificity of 86.1% (range, 81.0%–89.0%), PPV of 33.5% (range, 26.0%–40.0%), and NPV of 89.8% (range, 84.0%–95.0%). Although there are several scores (eg, FIB-4, NAFLD-FS, and APRI), FIB-4 is the most validated and outperforms other calculations in its ability to identify patients with a low probability of AF. Performance of serum-based NITs in cirrhosis improved in NPV. Using FIB-4 score, a cutoff of 1.92–2.48 in 439 patients had a sensitivity of 76.4% (range, 72.7%–80.0%), specificity of 82.4% (range, 76.0%–88.7%), PPV of 39.0% (range, 37.5%–40.4%), and NPV of 96.2% (range, 95.5%–96.9%). NAFLD-FS performance for a cutoff of –0.014 in 197 patients was sensitivity of 80%, specificity of 80.8%, PPV of 42.8%, and NPV of 95.7%. For a cutoff of 0.54–2.00 for APRI in 790 patients, sensitivity was 56.2% (range, 20.5%–77.3%), specificity was 83.6% (range, 56.3%–100%), PPV was 37.8% (range, 16.7%–100%), and NPV was 91.7% (range, 83.0%–96.7%). Despite some variability in the diagnostic profile of these serum-based tests, the consistent concordance in NPV for AF provides reassurance for their utilization in risk stratification16Morling J.R. Fallowfield J.A. Guha I.N. et al.Using non-invasive biomarkers to identify hepatic fibrosis in people with type 2 diabetes mellitus: the Edinburgh type 2 diabetes study.J Hepatol. 2014; 60: 384-391Abstract Full Text Full Text PDF PubMed Scopus (56) Google Scholar (Table 1).Table 1Noninvasive Tests and Accuracy for Advanced Fibrosis (F3–4) in Nonalcoholic Fatty Liver DiseaseNoninvasive testRecommended cutoff to rule in advanced hepatic fibrosisAF (F3–4) by biopsy, AUROC (95% CI)Serum FIB-4 score>2.670.83 (0.79–0.86) NAFLD-FS>0.6760.75 (0.71–0.79) APRI>0.840.76 (0.74–0.79) ELF>9.80.81 (0.77–0.85)Imaging VCTE, kPa>12.00.93 (0.89–0.96) SWE, kPa>8.00.89 (0.80–0.98) MRE, kPa>3.60.93 (0.90–0.96)AUROC, area under receiver operating curve. Open table in a new tab AUROC, area under receiver operating curve. Evaluation of VCTE M-probe performance for AF within the same meta-analysis in 1540 patients from 9 studies using a cutoff of 7.6–8 kPa had a sensitivity of 88.9% (range, 65.0%–100.0%), specificity of 77.2% (range, 65.9%–90.2%), PPV of 43.4% (range, 27.0%–52.0%), and NPV of 95.5% (range, 86.0%–100%). VCTE XL-probe performance at a cutoff of 5.7–9.3 from 3 studies of 579 patients had a sensitivity of 75.3% (range, 57.0%–91.0%), specificity of 74.0% (range, 54.0%–90.0%), PPV of 58.7% (range, 45.0%–71.0%), and NPV of 88.7% (range, 84.0%–93.0%). In cirrhosis, test performance similarly improved; a VCTE cutoff of 10.3–11.3 in 1362 patients had a sensitivity of 87.7% (range, 78.0%–100%), specificity of 86.3% (range, 82.0%–90.0%), PPV of 46.8% (range, 33.0%–75.0%), and NPV of 98.0% (range, 94.0%–100%). For the XL-probe, a broader cutoff of 7.2–16 in 654 patients was associated with a sensitivity of 87.8% (71.0%–100%), specificity of 82.0% (70.0%–91.0%), PPV of 39.8% (range, 31.0%–53.0%), and NPV of 97.8% (range, 95.0%–100%). SWE and MRE also have excellent diagnostic performance in the identification of AF. For SWE detection of AF, cutoffs of 3.02–10.6 among 429 patients had a sensitivity of 89.9% (range, 88.2%–91.5%), specificity of 91.8% (range, 90.0%–94.0%), PPV of 88.2% (range, 83.3%–93.1%), and NPV of 93.4% (range, 92.6%–94.2%). Using a cutoff of 3.36 for the detection of cirrhosis in 181 patients, the sensitivity was 100%, specificity was 85.6%, PPV was 55.2%, and NPV was 100%. MRE detection of AF with a cutoff of 3.62–4.8 in 628 patients had a sensitivity of 85.7% (range, 74.5%–92.2%), specificity of 90.8% (range, 86.9%–93.3%), PPV of 71.0% (range, 67.9%–74.5%), and NPV 93.4% (range, 81.0%–98.1%). A liver stiffness measurement (LSM) cutoff of 4.15–6.7 for cirrhosis in 384 patients had a sensitivity of 86.6% (range, 80.0%–90.9%), specificity of 93.4% (range, 91.4%–94.5%), PPV of 53.4% (range, 44.4%–58.8%), and NPV of 98.8% (range, 98.1%–99.2%).15Xiao G. Zhu S. Xiao X. et al.Comparison of laboratory tests, ultrasound, or magnetic resonance elastography to detect fibrosis in patients with nonalcoholic fatty liver disease: a meta-analysis.Hepatology. 2017; 66: 1486-1501Crossref PubMed Scopus (538) Google Scholar Although MRE is not recommended as a first-line approach to risk stratification in a patient with NAFLD,10Kanwal F. Shubrook J.H. Adams L.A. et al.Clinical care pathway for the risk stratification and management of patients with nonalcoholic fatty liver disease.Gastroenterology. 2021; 161: 1657-1669Abstract Full Text Full Text PDF PubMed Scopus (151) Google Scholar, 11Cusi K. Isaacs S. Barb D. et al.American Association of Clinical Endocrinology Clinical Practice Guideline for the Diagnosis and Management of Nonalcoholic Fatty Liver Disease in Primary Care and Endocrinology Clinical Settings: Co-Sponsored by the American Association for the Study of Liver Diseases (AASLD).Endocr Pract. 2022; 28: 528-562Abstract Full Text Full Text PDF PubMed Scopus (175) Google Scholar, 12Rinella M.E. Neuschwander-Tetri B.A. Siddiqui M.S. et al.AASLD practice guidance on the clinical assessment and management of nonalcoholic fatty liver disease.Hepatology. 2023; 77: 1797-1835Crossref PubMed Scopus (101) Google Scholar it can be an important tool if clinical uncertainty exists, if there is a need for concomitant cross-sectional imaging, or when other elastography techniques are unavailable. The goal of testing algorithms is to establish or exclude a diagnosis with confidence. Indeterminate results require additional testing. For NITs, diagnostic performance is reported using area under receiver operating curve, sensitivity, and specificity. The clinical utility of guidance cutoffs is dependent on the prevalence of NAFLD in the target population. Primary care populations, endocrinology clinics, and gastroenterology practices are likely to differ in the prevalence of AF. Shah et al17Shah A.G. Lydecker A. Murray K. et al.Comparison of noninvasive markers of fibrosis in patients with nonalcoholic fatty liver disease.Clin Gastroenterol Hepatol. 2009; 7: 1104-1112Abstract Full Text Full Text PDF PubMed Scopus (949) Google Scholar compared FIB-4 score with 7 other serum-based NITs in a national database of predominantly Caucasian subjects with histologically confirmed NAFLD. Statistically significant differences between groups included female gender and nondiabetic status in the earlier stage (F1–2) vs AF (F3–4) cohorts. The sensitivity and specificity for AF using a low cutoff of <1.30 in this population were 74% and 71%, respectively. More importantly, the NPV was 90% in the studied population. When applied predictively to a variable prevalence of AF, the NPV increased to 96% with a prevalence of 10% and dropped to 73% with 50% prevalence. In the comparison of NITs that follows, it is important to remember than the NPV and PPV reported are functions of disease prevalence, hence, the context of use within specialty clinics vs the general population is an important distinction. One notable limitation for FIB-4 score is the proportion of scores in the indeterminate range in some populations.18Sun W. Cui H. Li N. et al.Comparison of FIB-4 index, NAFLD fibrosis score and BARD score for prediction of advanced fibrosis in adult patients with non-alcoholic fatty liver disease: a meta-analysis study.Hepatol Res. 2016; 46: 862-870Crossref PubMed Scopus (150) Google Scholar Despite this, given the general population prevalence of NAFLD at 30%, it is reasonable to choose a cutoff of <1.3 to augment other clinical measurements to exclude most individuals with AF.f Furthermore, FIB-4 score is influenced by age and therefore performs poorly in patients younger than 35 years or older than 65 years. When used alone, FIB-4 score has poor diagnostic accuracy in younger patients and low specificity in older adults.19Mosca A. Della Volpe L. Alisi A. et al.Non-invasive diagnostic test for advanced fibrosis in adolescents with non-alcoholic fatty liver disease.Front Pediatr. 2022; 10885576Crossref Scopus (4) Google Scholar,20van Kleef L.A. Sonneveld M.J. de Man R.A. et al.Poor performance of FIB-4 in elderly individuals at risk for chronic liver disease - implications for the clinical utility of the EASL NIT guideline.J Hepatol. 2022; 76: 245-246Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar Given the heterogeneity of NAFLD in diverse populations, overreliance on 1 NIT may reduce sensitivity in identifying individuals with AF and cirrhosis in both primary care and specialist contexts. When imaging biomarkers are not readily available in clinical practice, a second serum biomarker, such as ELF, may be considered.12Rinella M.E. Neuschwander-Tetri B.A. Siddiqui M.S. et al.AASLD practice guidance on the clinical assessment and management of nonalcoholic fatty liver disease.Hepatology. 2023; 77: 1797-1835Crossref PubMed Scopus (101) Google Scholar A primary care referral pathway in the United Kingdom using FIB-4 score <1.30 as a determination for AF with comprehensive review revealed the benefit of sequential testing.21Srivastava A. Gailer R. Tanwar S. et al.Prospective evaluation of a primary care referral pathway for patients with non-alcoholic fatty liver disease.J Hepatol. 2019; 71: 371-378Abstract Full Text Full Text PDF PubMed Scopus (256) Google Scholar Of 1452 patients over 2 years, 1022 (71.3%) had an F