Diagnosing and staging Metabolic Dysfunction-Associated Steatohepatitis (MASH) has become one of the most pressing challenges in hepatology today. As the prevalence of MASH rises globally, now recognized as a progressive form of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD), the demand for accurate, scalable diagnostic tools is intensifying. With the conditional approval of therapies such as resmetirom, precise identification of patients with moderate fibrosis (F2–F3) is no longer optional; it’s essential for optimizing treatment outcomes, minimizing healthcare costs, and advancing clinical research.
However, existing diagnostic pathways, including non-invasive tests (NITs) and conventional histology, are fraught with limitations. Below, we explore the multifaceted challenges in diagnosing and staging MASH and highlight innovative solutions aimed at improving diagnostic accuracy across clinical and research settings.
Understanding MASH: A Redefined Hepatic Condition
From NASH to MASH: Why the Terminology Shift Matters
The transition from Non-Alcoholic Steatohepatitis (NASH) to Metabolic Dysfunction-Associated Steatohepatitis (MASH) marks more than just a semantic update. It reflects an evolving understanding of liver disease within the metabolic syndrome spectrum. The reclassification under MASLD (Metabolic Dysfunction-Associated Steatotic Liver Disease) now provides a more inclusive and clinically accurate framework, recognizing cardiometabolic risk as a key driver of disease progression.
Core Diagnostic Criteria for MASH
To confirm a diagnosis of MASH, a patient must exhibit:
- Hepatic steatosis, typically >5%
- Evidence of hepatocyte ballooning
- Lobular inflammation
- Fibrosis, typically stage F2–F3 for treatment eligibility
These core features guide both diagnostic confirmation and patient selection for therapeutic intervention.
Limitations of Current Diagnostic Methods
Non‑Invasive Tests (NITs): Useful, but Not Definitive
NITs such as FIB-4, liver stiffness measurement (LSM), and FAST score are increasingly used in clinical practice. However, their diagnostic performance remains inconsistent.
The main challenge with NITs is their limited sensitivity and specificity for detecting MASH with moderate to advanced fibrosis F2 to F3. A high inaccuracy rate between NITs and liver biopsies in prescribing Resmetirom has been reported in a recent Turkish cohort study¹:
- 62–73% of patients with biopsy-confirmed MASH (F2–F3) were missed by NITs.
- Up to 44% of patients were overprescribed treatment based on NITs alone.
Furthermore, discordance among non-invasive tests particularly between serum biomarkers and imaging modalities is a recognised limitation often leading to conflicting results especially at intermediate fibrosis stages F2 to F2. This highlights that relying on NITs alone in real-world practice may lead to inaccuracies and increased economic burden. Such misalignment presents both clinical and economic risks, especially when expensive treatments like resmetirom are involved.
For this reason liver biopsy analysis remains essential at least in selected cases.
Standard Histology: The Reproducibility Challenge
Standard histology also poses well-recognized limitations . It employs semi-quantitative ordinal scoring systems that are inherently subjective. Even in expert centers, pathologist disagreement on staging and grading is well documented. Additionally, variability in staining methods further reduces reproducibility across sites.
Together, the limitations of both NITs and standard histology may lead to overtreatment and misdiagnosis of MASH.
With high costs and the potential for overprescription at stake, accurate and reproducible patient identification has become critical in the era of FDA-approved therapies.
Staging Fibrosis in MASH: Why Accuracy is Critical
Disease Progression and Treatment Eligibility
Both resmetirom (Rezdiffra) and Wegovy have received FDA approval for treating patients with MASH at fibrosis stages F2 to F3. This makes precise staging a clinical gatekeeper for therapy access.
A recent study in Hepatology Communications² estimates that up to 8.3 million U.S. adults may qualify for Resmetirom based on current eligibility criteria.
However, imprecise staging risks undertreatment of eligible patients and overtreatment of those unlikely to benefit, placing a burden on healthcare systems.
Challenges with Current Fibrosis Scoring Systems
Histological scoring systems like NAS or SAF, while widely used, often:
- Rely on ordinal rather than continuous measurements
- Are not designed for treatment response monitoring
These limitations complicate both clinical decision-making and endpoint assessment in trials.
Emerging Solutions in MASH Diagnostics
The Value of Label-Free Tissue Imaging
Label‑free imaging technologies offer a new approach to histological analysis. HistoIndex’s Second Harmonic Generation (SHG) and Two‑Photon Excitation Fluorescence (TPEF) imaging visualize tissue micro‑architecture without chemical stains, reducing variability introduced during sample preparation.
Key advantages include:
Better preservation of tissue architecture
Faster turnaround times
Reduced batch-to-batch inconsistency
By eliminating staining‑related variability, label‑free imaging creates a stronger foundation for objective, quantitative analysis.
AI-Based Analysis for Accurate Liver Fibrosis Assessment
HistoIndex’s high quality SHG/TPEF images form the foundation for different types of quantitative assessments including the AI-driven algorithm qFibrosis® – HistoIndex’s proprietary tool for liver fibrosis quantification in patients with MASH.
The qFibrosis® AI model generates fibrosis scores on a continuous scale.
It has been validated across thousands of MASH clinical trial samples, including the Phase 3 resmetirom MAESTRO-NASH trial.
qFibrosis® powers HistoIndex’s Laboratory Developed Test (LDT) FibroSIGHT™ Plus, which brings automated quantitative analysis of liver fibrosis to routine patient care.
Partner with HistoIndex for Advanced MASH Diagnostics
As precision medicine accelerates in hepatology, accurate diagnosis and staging of MASH are critical. At HistoIndex, we support clinicians and researchers with AI-powered, label-free tissue imaging that transforms how fibrosis is detected, measured, and monitored.
By partnering with us, you’ll gain access to the next generation of quantitative pathology tools, designed to optimize clinical trial outcomes and advance liver disease care.
Contact our team to discuss how our technology can support your research or practice.
MASH Diagnostics FAQs
MASH (Metabolic Dysfunction-Associated Steatohepatitis) replaces NASH to better reflect the metabolic origins of the disease.
Staging determines treatment eligibility. FDA-approved drugs like Resmetirom require fibrosis stage F2–F3.
Low sensitivity, poor specificity, and lack of standardized thresholds make NITs unreliable for treatment decisions.
Taking into account the limitations of NITs, which may lead to overtreatment and misdiagnosis of MASH, liver biopsies remain essential in selected cases.
NITs have limited sensitivity and specificity for detecting MASH with moderate to advanced fibrosis F2 to F3. Discordance among non-invasive tests particularly between serum biomarkers and imaging modalities is a recognised limitation often leading to conflicting results especially at intermediate fibrosis stages F2 to F2.
HistoIndex uses SHG and TPEF imaging combined with AI algorithms to analyze and quantify liver fibrosis in liver biopsy samples.
Digital pathology reduces inter-reader variability and provides objective, continuous measurements instead of subjective scores.
References
- Kaya, E., Aksoy, S., Oruc, N., Tasdemir, C., Cengiz, B.I., Keklikkiran, C., & Yilmaz, Y. (2025). Non-invasive tests for resmetirom treatment fail to accurately define the target population: Evidence from a biopsy-proven MASLD cohort. Hepatology Forum, 6(3), 111–115.
- Le, Phuc, et al. “Resmetirom-eligible population among US adults: An estimation analysis based on NHANES 2017–March 2020.” Hepatology communications 9.7 (2025): e0755.