A sequential testing strategy that combines the FIB-4 index with the serum biomarker M2BPGi improved detection of advanced fibrosis in patients with metabolic dysfunction–associated steatotic liver disease, while reducing unnecessary follow-up testing, according to a multicenter study of nearly 1,000 patients.
In the retrospective cohort of 992 patients with biopsy-confirmed disease across 17 centers in Japan, investigators found that M2BPGi (Mac-2 binding protein glycosylation isomer) outperformed commonly used noninvasive tests and, when added to FIB-4, reduced referrals for further evaluation by about 36% while maintaining a false-negative rate of 14%.
The study, published in Gastro Hep Advances, evaluated patients who underwent liver biopsy and same-day laboratory testing. Advanced fibrosis (stages F3-4) was present in 26% of the cohort. Serum M2BPGi levels increased with worsening steatosis, inflammation, hepatocyte ballooning, and fibrosis stage, demonstrating correlation with histopathologic severity.
For detecting advanced fibrosis, M2BPGi showed stronger diagnostic performance than FIB-4 or the aspartate aminotransferase-to-platelet ratio index (APRI). The area under the curve was 0.77 for M2BPGi versus 0.72 for FIB-4 and 0.67 for APRI. At a cutoff of about 1, M2BPGi achieved 76% sensitivity and 65% specificity, compared with 67% sensitivity and 58% specificity for FIB-4.
At commonly used lower thresholds, FIB-4 maintained a high negative predictive value (89%) but had limited positive predictive value (33%). M2BPGi improved specificity and positive predictive value (43%) while maintaining a similar negative predictive value (88%).
The clinical utility was most evident in patients with intermediate FIB-4 scores (1.3–2.67), a group that often requires additional testing. In this subgroup, adding M2BPGi increased specificity from 42% to 68% while maintaining sensitivity at 72%, helping better distinguish patients who need referral.
A decision-tree analysis supported a two-step approach: initial stratification with FIB-4 followed by M2BPGi testing. This algorithm reduced the number of patients needing further evaluation by about one-third while preserving acceptable diagnostic accuracy.
Subgroup analyses showed consistent performance across patient groups. M2BPGi maintained similar accuracy in patients with and without diabetes, though performance was slightly lower in those with diabetes. Higher alanine aminotransferase levels modestly reduced diagnostic accuracy, suggesting some influence of hepatic inflammation. In patients with obesity, M2BPGi continued to outperform FIB-4 and APRI.
Multivariable analysis identified M2BPGi, body mass index, alanine aminotransferase, and platelet count as independent predictors of advanced fibrosis, supporting its role alongside established clinical markers.
For practicing gastroenterologists and hepatologists, the findings address a common limitation of FIB-4: its large indeterminate zone. Incorporating M2BPGi may refine risk stratification in primary and specialty care settings, potentially reducing reliance on liver biopsy and advanced imaging.
The authors acknowledged several limitations of the study, including its retrospective design, lack of external validation, and inclusion of only Japanese patients, which may limit generalizability. The study also did not compare other emerging biomarkers or imaging modalities.
“Integrating M2BPGi into FIB-4–based screening approaches … has the potential to enhance diagnostic precision while minimizing the reliance on liver biopsies and reducing unnecessary referrals,” the investigators concluded.
The study was funded by Siemens Healthcare Diagnostics K.K. Several authors reported relationships with pharmaceutical and diagnostics companies, including speaker fees and research grants; one author is employed by Siemens Healthcare Diagnostics.
Expert Insight
GI & Hepatology News invited Prooksa Ananchuensook, MD, MSc, of the Division of Gastroenterology in the Department of Internal Medicine at Chulalongkorn University, Bangkok, Thailand, to comment on the study’s findings.
Why is this study important?
Dr. Ananchuensook: This study is important because advanced fibrosis in MASLD is a key predictor of mortality, highlighting the need for accurate, non-invasive tools (NITs) for early assessment and risk stratification, particularly in non-GI settings to guide referral.1 M2BPGi, a blood-based biomarker associated with hepatic stellate cell activation, has emerged as a potential tool for fibrosis assessment.2 In this study, the authors evaluated the diagnostic performance of M2BPGi in MASLD, compared it with FIB-4, identified an optimal cutoff for advanced fibrosis, and proposed a sequential approach that reduced unnecessary referrals by 36%.
How might the findings influence clinical practice?
Dr. Ananchuensook: Current guidelines recommend FIB-4 as a first-line tool (cut-off <1.3) to exclude up to 90% of advanced fibrosis in MASLD in primary care due to its acceptable performance, simplicity and lack of need for additional laboratory testing or cost. 3-5 Patients with FIB-4 of 1.3 or greater, particularly those at intermediate risk (1.3–2.67), typically undergo second-step assessment with vibration-controlled transient elastography (VCTE), a point-of-care imaging modality, or alternative blood-based biomarkers such as the Enhanced Liver Fibrosis (ELF) test. Although not directly compared with VCTE or other modalities, a sequential approach incorporating M2BPGi showed acceptable performance and may reduce referrals while maintaining a relatively low false-negative rate, suggesting a potential role as a complementary marker to FIB-4 and as a triage option when VCTE is unavailable. However, M2BPGi is more widely used in East Asia and is not yet commonly adopted in the United States, which may limit its availability and highlights the need for validation in broader populations.6
Where are the knowledge gaps, and what still needs investigation?
Dr. Ananchuensook: Several important knowledge gaps remain. The absence of an external validation cohort is a key limitation that restricts the generalizability of the proposed M2BPGi cut-off of 1 for detecting advanced fibrosis in MASLD. In addition to lower thresholds, the identification and evaluation of upper cutoff values are warranted to better define its role in ruling out and ruling in advanced fibrosis and cirrhosis. Moreover, further studies are needed to assess its performance in specific subgroups, such as individuals with obesity, in whom the accuracy of vibration-controlled transient elastography (VCTE) may be reduced, while M2BPGi appears to be less affected by body mass index.7 Finally, cost-effectiveness analyses in comparison with other non-invasive modalities are essential to define its role in clinical practice. Beyond its diagnostic value, longitudinal studies are needed to establish the prognostic utility of M2BPGi in predicting progression to cirrhosis and hepatocellular carcinoma in MASLD.
Is there anything else you’d like to say about this work?
Dr. Ananchuensook: This study reinforced the role of NITs, particularly blood-based biomarkers, to triage MASLD patients with advanced fibrosis in primary care and guide referral to gastroenterology and hepatology services. In this context, M2BPGi, with an optimal cut-off of 1, represents a promising biomarker for noninvasive fibrosis assessment in MASLD by demonstrating performance comparable to FIB-4 and the potential to refine second-step risk stratification, particularly in those at intermediate risk. However, its role in routine practice remains to be defined pending broader validation and real-world adoption.
Dr. Ananchuensook reported having no disclosures.
References
Younossi ZM, De Avila L, Petta S, et al. Predictors of fibrosis, clinical events, and mortality in MASLD: data from the Global-MASLD study. Hepatology. 2025; doi:10.1097.
Shirabe K, Bekki Y, Gantumur D, et al. Mac-2 binding protein glycan isomer (M2BPGi) is a new serum biomarker for assessing liver fibrosis: more than a biomarker of liver fibrosis. J Gastroenterol. 2018;53:819-826.
Kanwal F, Neuschwander-Tetri BA, Loomba R, et al. Metabolic dysfunction-associated steatotic liver disease: update and impact of new nomenclature on the American Association for the Study of Liver Diseases practice guidance on nonalcoholic fatty liver disease. Hepatology. 2024;79:1212-1219.
Shah AG, Lydecker A, Murray K, et al. Use of the FIB-4 index for noninvasive evaluation of fibrosis in nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol. 2009;7:1104.
Tacke F, Horn P, Wong VW-S, et al. EASL–EASD–EASO clinical practice guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD). J Hepatol. 2024;81:492-542.
Jun T, Hsu YC, Ogawa S, et al. Mac-2 binding protein glycosylation isomer as a hepatocellular carcinoma marker in patients with chronic hepatitis B or C infection. Hepatol Commun. 2019;3:493-503.
Ananchuensook P, Moonlisarn K, Boonkaew B, et al. Diagnostic performance of serum Mac-2–binding protein glycosylation isomer as a fibrosis biomarker in nonobese and obese patients with MASLD. Biomedicines. 2025;13:415.