AGILE 3+ and AGILE 4 Scores: Calculator, Formulas & Clinical Interpretation

1. Introduction

The identification of patients with advanced fibrosis and cirrhosis remains a critical challenge in the management of metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD).

While liver biopsy remains the gold standard for fibrosis staging, its invasiveness, sampling variability, and cost have driven the development of non-invasive tests (NITs) for risk stratification.

Currently available NITs, including the Fibrosis-4 Index (FIB-4) and liver stiffness measurement by vibration-controlled transient elastography (LSM-VCTE), are highly effective at excluding advanced fibrosis (≥F3) or cirrhosis.

However, these tools have only moderate ability to rule in these conditions, with high false positive rates and a substantial proportion of patients falling into indeterminate zones requiring further testing or liver biopsy.

To address these limitations, Sanyal and colleagues developed two novel FibroScan-based composite scores, Agile 3+ and Agile 4, designed to identify advanced fibrosis and cirrhosis, respectively, with optimized positive predictive value and fewer indeterminate results (Sanyal et al., 2023).

2. Development and Validation

The Agile scores were developed through an international multicenter study that included seven adult cohorts with suspected NAFLD who underwent liver biopsy, LSM by VCTE, and blood sampling during routine clinical practice or screening for therapeutic trials (Sanyal et al., 2023).

The study population was randomly divided into training and internal validation sets to build and assess the best-fitting logistic regression models. Both scores were subsequently validated in two large external cohorts, including the NASH Clinical Research Network (NASH CRN) cohort and a French NAFLD cohort.

The development goals were to:

1. Optimize sensitivity and specificity for diagnosis of advanced fibrosis (Agile 3+) or cirrhosis (Agile 4)
2. Maximize positive predictive value (PPV)
3. Reduce the proportion of individuals with indeterminate results

3. Components of the Agile Scores

Both Agile scores combine liver stiffness measurement with clinical and laboratory parameters readily available in routine practice.

3.1 Common Components

4. Agile 3+ Score

4.1 Agile 3+ Purpose

Agile 3+ is designed to detect advanced fibrosis (≥F3) in patients with NAFLD/MASLD.

4.2 Agile 3+ Formula

The Agile 3+ score is calculated using a logistic regression model:

Agile 3+ = e^logit / (1 + e^logit)

Where:

logit = −3.92368 + 2.29714 × ln(LSM) − 0.00902 × PLT − 0.98633 × (1/AAR) + 1.08636 × Diabetes − 0.38581 × Sex + 0.03018 × Age

Variables: - LSM = Liver stiffness measurement (kPa) - PLT = Platelet count (×10⁹/L) - AAR = AST/ALT ratio - Diabetes = 1 if diabetic, 0 if not - Sex = 1 if male, 0 if female - Age = Age in years

Agile 3+ Interpretation

Agile 3+ Performance Characteristics

In the original validation studies, Agile 3+ demonstrated:

• AUROC: 0.86–0.90 for advanced fibrosis
• Sensitivity: 87% at the rule-out threshold (0.451)
• Specificity: 91% at the rule-in threshold (0.679)
• Indeterminate zone: Reduced to approximately 8–13% of patients

5. Agile 4 Score

5.1 Agile 4 Purpose

Agile 4 is designed to detect cirrhosis (F4) in patients with NAFLD/MASLD.

5.2 Agile 4 Formula

The Agile 4 score is calculated using a logistic regression model:

Agile 4 = e^logit / (1 + e^logit)

Where:

logit = 7.50139 − 15.42498 × (1/√LSM) − 0.01378 × PLT − 1.41149 × (1/AAR) − 0.53281 × Sex + 0.41741 × Diabetes

Variables:

• LSM = Liver stiffness measurement (kPa)
• PLT = Platelet count (×10⁹/L)
• AAR = AST/ALT ratio
• Sex = 1 if male, 0 if female
• Diabetes = 1 if diabetic, 0 if not

Note: Agile 4 uses the inverse square root of LSM (1/√LSM), whereas Agile 3+ uses the natural logarithm of LSM.

5.3 Agile 4 Interpretation

5.4 Agile 4 Performance Characteristics

In the original validation studies, Agile 4 demonstrated: - AUROC: 0.89–0.93 for cirrhosis - Sensitivity: 79% at the rule-out threshold (0.251) - Specificity: 96% at the rule-in threshold (0.565) - Indeterminate zone: Reduced to approximately 10–15% of patients

6. Clinical Advantages Over Existing Tests

6.1 Comparison with FIB-4 and LSM Alone

6.2 Key Benefits of Agile 3+ and Agile 4

1. Smaller indeterminate zone: Fewer patients require additional testing or liver biopsy
2. Higher positive predictive value: Greater confidence when ruling in advanced fibrosis or cirrhosis
3. Validated internationally: Performance confirmed across multiple ethnicities and geographic regions
4. Free to calculate: Available through the myFibroScan app and online calculators
5. Prognostic value: Both scores predict liver-related events, including decompensation, HCC, and death (Lin et al., 2024)

7. Prognostic Value

Beyond diagnosis, the Agile scores have demonstrated prognostic utility. In a study by Lin and colleagues published in JAMA, VCTE-based scores including Agile 3+ and Agile 4 were shown to predict liver-related events in patients with steatotic liver disease (Lin et al., 2024).

Patients in the Agile 3+ rule-in group (≥0.679) had significantly higher hazard ratios for liver-related events compared to those in the rule-out group. Similarly, Agile 4 rule-in status was associated with markedly increased risk of hepatocellular carcinoma and hepatic decompensation.

8. Limitations

While the Agile scores represent a significant advancement, clinicians should be aware of their limitations:

1. Require FibroScan: Not suitable for settings without VCTE availability
2. Developed for NAFLD/MASLD: Performance may differ in other liver disease etiologies
3. Obesity considerations: Probe selection (M vs. XL) may affect LSM values
4. Acute inflammation: Recent alcohol intake, acute hepatitis, or biliary obstruction can falsely elevate LSM
5. Cannot replace biopsy entirely: Patients with indeterminate results may still require histological assessment

9. Practical Application

9.1 When to Use Agile Scores

• Secondary/tertiary care: For patients referred with suspected advanced liver disease
• Clinical trial enrollment: To identify candidates for MASH therapeutic trials
• Risk stratification: To prioritize patients for surveillance (HCC screening, variceal surveillance)
• Treatment decisions: To guide intensity of lifestyle interventions and pharmacotherapy

9.2 Clinical Workflow

1. Obtain FibroScan: Ensure fasting state and use appropriate probe
2. Collect laboratory values: AST, ALT, platelet count
3. Document clinical data: Age, sex, diabetes status
4. Calculate scores: Using online calculator or myFibroScan app
5. Interpret results: Apply dual cutoff strategy for rule-out and rule-in
6. Clinical decision: Based on score zone and clinical context

10. Combined Agile 3+ and Agile 4 Calculators

11. Summary

The Agile 3+ and Agile 4 scores represent the current state-of-the-art for non-invasive identification of advanced fibrosis and cirrhosis in patients with MASLD. By combining FibroScan-based liver stiffness measurement with readily available clinical and laboratory parameters, these scores achieve superior diagnostic accuracy, smaller indeterminate zones, and higher positive predictive values compared to existing tests.

The free availability of these scores through the myFibroScan application and their validation across diverse populations make them practical tools for implementation in clinical practice. As the field continues to evolve with the approval of pharmacotherapies for MASH, accurate risk stratification using tools like the Agile scores will become increasingly important for patient selection and monitoring.

12. References

1. Sanyal AJ, Foucquier J, Younossi ZM, et al. Enhanced diagnosis of advanced fibrosis and cirrhosis in individuals with NAFLD using FibroScan-based Agile scores. J Hepatol. 2023;78(2):247-259. https://doi.org/10.1016/j.jhep.2022.10.034

2. Lin H, Lee HW, Yip TC, et al. Vibration-Controlled Transient Elastography Scores to Predict Liver-Related Events in Steatotic Liver Disease. JAMA. 2024;331(15):1287-1297. https://pubmed.ncbi.nlm.nih.gov/38512249/

3. Pennisi G, Enea M, Pandolfo A, et al. AGILE 3+ Score for the Diagnosis of Advanced Fibrosis and for Predicting Liver-related Events in NAFLD. Clin Gastroenterol Hepatol. 2023;21(5):1293-1302.e5. https://doi.org/10.1016/j.cgh.2022.06.013

4. Tacke F, Horn P, Wong VW, et al. EASL–EASD–EASO Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD). J Hepatol. 2024;81(3):492-542. https://doi.org/10.1016/j.jhep.2024.04.031

5. Miura K, Hayashi H, Kamada Y, et al. Agile 3+ and Agile 4, noninvasive tests for liver fibrosis, are excellent formulae to predict liver-related events in nonalcoholic fatty liver disease. Hepatol Res. 2023;53(10):978-988. https://doi.org/10.1111/hepr.13938

Educational Use Disclaimer: This article and any associated calculator tools are provided for educational and informational purposes only. They are not registered medical devices and should not be used for clinical decision-making or direct patient care. Healthcare professionals requiring validated clinical tools should use the official myFibroScan® application by Echosens, which is an FDA-registered Class I medical device. Formulas presented herein are reproduced from published peer-reviewed literature under Creative Commons licensing for educational purposes.

Note: This article reflects evidence available through early 2025. Given the rapidly evolving landscape of noninvasive testing in MASLD, readers are encouraged to consult current guidelines for the most up-to-date recommendations.