FIB-4 Score Applications and Interpretations

Primary Clinical Applications

• The FIB-4 score is a validated blood-based calculator used to noninvasively assess the risk of advanced liver fibrosis in patients with chronic liver disease, serving as a first-line screening tool to identify who needs further evaluation or specialist referral, as recommended by the American Gastroenterological Association 1, 2
• FIB-4 is the most validated and recommended first-line noninvasive test for identifying patients at low or high probability of advanced fibrosis in chronic liver disease, according to the American Association for the Study of Liver Diseases 1, 2
• The score uses four readily available laboratory values: age, AST, ALT, and platelet count, making it simple, inexpensive, and accessible in any clinical setting, as noted by the European Association for the Study of the Liver 1, 3
• FIB-4 performs best at ruling out advanced fibrosis rather than confirming it, with negative predictive values exceeding 90% at appropriate cutoffs, as reported by the American Gastroenterological Association 1, 2

Disease-Specific Cutoff Values

• For NAFLD, FIB-4 <1.3 (or <2.0 if age ≥65 years) reliably excludes advanced fibrosis, and these patients can be reassessed in 2-3 years, as recommended by the American Association for the Study of Liver Diseases 2, 3, 4
• FIB-4 1.3-2.67 represents an indeterminate zone requiring secondary testing with elastography or enhanced liver fibrosis testing, according to the European Association for the Study of the Liver 2, 3
• FIB-4 >2.67 indicates high risk for advanced fibrosis and warrants hepatology referral for further evaluation, as noted by the American Gastroenterological Association 2, 4

Prognostic Value Beyond Diagnosis

• Elevated FIB-4 scores are strongly associated with future liver-related complications, including hepatocellular carcinoma, liver decompensation, liver transplantation, and death, as reported by the American Association for the Study of Liver Diseases 1

Clinical Implementation Algorithm

• All patients with NAFLD, metabolic syndrome, type 2 diabetes, chronic viral hepatitis, or unexplained elevated liver enzymes should have FIB-4 calculated, as recommended by the American Gastroenterological Association 2, 4
• Low-risk patients (<1.3 for age <65, or <2.0 for age ≥65) can be reassessed in 2-3 years, while indeterminate-risk patients (1.3-2.67) require secondary testing, and high-risk patients (>2.67) should be referred to hepatology, according to the American Association for the Study of Liver Diseases 2, 4

Important Limitations and Caveats

• FIB-4 performs poorly in patients younger than 35 years and may require adjusted cutoffs in those ≥65 years, as noted by the European Association for the Study of the Liver 3, 5
• FIB-4 has lower accuracy in alcoholic liver disease and autoimmune hepatitis compared to viral hepatitis and NAFLD, as reported by the American Association for the Study of Liver Diseases 3
• While FIB-4 is excellent for excluding advanced fibrosis, it has only moderate positive predictive value for confirming advanced disease, according to the American Gastroenterological Association 1, 6

Comparison to Other Noninvasive Tests

• FIB-4 outperforms APRI for detecting both F2-F4 and F3-F4 fibrosis stages, as reported by the American Association for the Study of Liver Diseases 6
• FIB-4 is recommended as first-line due to simplicity and zero cost, although it may not outperform proprietary tests like ELF or imaging-based elastography, according to the American Gastroenterological Association 1

Noninvasive Assessment of Liver Fibrosis

Introduction to FIB-4 and APRI

• The American Association for the Study of Liver Diseases recommends using FIB-4 and APRI as simple, blood-based, noninvasive scoring systems to assess the severity of liver fibrosis in patients with chronic liver disease 7
• FIB-4 and APRI use routine laboratory values, such as age, AST, ALT, and platelet count, to evaluate liver fibrosis, with FIB-4 being the most validated and recommended first-line noninvasive test 7

Diagnostic Performance of FIB-4 and APRI

• In chronic hepatitis C, FIB-4 demonstrated an AUC of 0.84 for diagnosing cirrhosis, outperforming APRI 8
• APRI uses AST level and platelet count in its calculation and has a simpler formula than FIB-4, but may be less accurate in certain populations 7, 8
• For significant fibrosis, APRI showed sensitivity of 82% and specificity of 57% at low cutoff values of 0.4-0.78 8
• For cirrhosis, APRI demonstrated sensitivity of 77% and specificity of 78% at low cutoff values of 0.75-1.0 8

Comparative Performance and Limitations

• FIB-4 demonstrates superior diagnostic performance compared to APRI, particularly for diagnosing cirrhosis 8
• APRI has suboptimal diagnostic performance in primary biliary cholangitis, with AUCs of 0.64-0.69 for various fibrosis stages 9
• Both scores have significant limitations, including age effects, inflammation, and disease-specific accuracy, which must be considered when interpreting results 8

FIB-4 Index with Reflex to Enhanced Liver Fibrosis (ELF) Score

Initial Assessment with FIB-4

• The American Gastroenterological Association recommends using FIB-4 as the first-line screening test for patients undergoing evaluation for liver fibrosis, then reflex to ELF testing for those with indeterminate FIB-4 scores to accurately identify advanced fibrosis and reduce unnecessary referrals and liver biopsies 10, 11
• Calculate FIB-4 for all patients with suspected NAFLD or chronic liver disease using the formula: (age × AST)/(platelets × √ALT) 10, 11

Reflex to ELF Testing

• When FIB-4 falls in the indeterminate range, automatically perform ELF testing to improve diagnostic accuracy and reduce unnecessary specialist referrals 10, 11
• ELF <7.7 indicates low risk for advanced fibrosis, and patients should continue primary care management with serial monitoring 12
• ELF ≥9.8 indicates high risk for advanced fibrosis, and patients should be referred to hepatology for comprehensive evaluation, including consideration of liver biopsy, hepatocellular carcinoma surveillance, and variceal screening 10, 11, 12

Diagnostic Performance

• No relevant facts with citations

Clinical Benefits of the Sequential Approach

• No relevant facts with citations

Important Caveats

• FIB-4 has reduced accuracy in patients <35 years old due to age-dependent calculations, and adjusted cutoffs are necessary for those ≥65 years to avoid overestimating fibrosis risk 13, 14

When to Consider Alternative Testing

• If ELF testing is unavailable or results are discordant with clinical suspicion, proceed directly to VCTE (FibroScan) or magnetic resonance elastography (MRE) for liver stiffness measurement 13, 14, 12
• VCTE cutoffs for advanced fibrosis: ≥8.0-12.0 kPa suggests significant fibrosis; ≥12.0 kPa suggests advanced fibrosis; ≥15.0 kPa suggests cirrhosis; ≥20-25 kPa suggests clinically significant portal hypertension 10, 12

Management Based on Results

• For low-risk patients (low FIB-4 or low ELF), implement lifestyle modifications targeting 7-10% weight loss, 150-300 minutes weekly moderate-intensity exercise, and address metabolic risk factors, and reassess with FIB-4 every 2-3 years 10, 11, 14
• For high-risk patients (high FIB-4 and high ELF), immediate hepatology referral for initiation of hepatocellular carcinoma surveillance, variceal screening via upper endoscopy, consideration of pharmacotherapy, and aggressive cardiovascular risk management 12

Liver Fibrosis Diagnosis and Management

Diagnostic Criteria

• The European Association for the Study of the Liver recommends using the FIB-4 score to diagnose liver fibrosis, with a score of 1.3-2.67 indicating an indeterminate result that requires further evaluation with a FibroScan 15, 16
• The American Association for the Study of Liver Diseases suggests that a FIB-4 score >2.67 indicates a high risk of advanced fibrosis and justifies a referral to a hepatologist for complete evaluation 15, 16
• The FIB-4 score has a sensitivity of 69.1% and specificity of 70.5% for advanced fibrosis (≥F3) in patients with chronic hepatitis B 15, 16
• A FIB-4 score >3.25 has a specificity of 95.3% for advanced fibrosis, justifying a FibroScan for confirmation 15, 16

FibroScan Performance

• The FibroScan demonstrates excellent performance for detecting advanced fibrosis when used after an indeterminate or high FIB-4 score, with a sensitivity of 75.1% and specificity of 79.3% for significant fibrosis (≥F2) 15, 16
• The FibroScan has a likelihood ratio of 5.4 for advanced fibrosis (≥F3) when the score is >8.0-11.0 kPa 15, 16
• The FibroScan has a likelihood ratio of 7.5 for cirrhosis (F4) when the score is >11.0-14.0 kPa 15, 16

Patient Evaluation

• Patients with chronic hepatitis C and a FIB-4 score >3.25 suggest advanced fibrosis with a specificity of 85-90% 17, 18
• Patients with non-alcoholic fatty liver disease (NAFLD) and a FIB-4 score >2.67 are at high risk and require evaluation with a FibroScan and referral to a hepatologist 15, 16

Management of Mildly Coarsened Liver Echotexture with Low FIB-4 Score

Initial Risk Stratification

• A low FIB-4 score (<1.3, or <2.0 if age ≥65 years) reliably excludes advanced fibrosis with >90% negative predictive value, so reassess with repeat FIB-4 testing in 2-3 years while implementing lifestyle modifications targeting metabolic risk factors, as recommended by the American Gastroenterological Association 19
• FIB-4 <1.3 (or <2.0 if ≥65 years) has a negative predictive value exceeding 90% for excluding advanced fibrosis, making further immediate evaluation unnecessary in most cases, according to the American College of Gastroenterology 19
• Ultrasound findings of coarsened echotexture indicate steatosis but do not correlate with fibrosis stage, so the FIB-4 score takes precedence for risk stratification, as stated by the American Institute for Gastroenterology 19

Surveillance Timeline Based on Metabolic Risk

• Without diabetes or multiple metabolic risk factors, repeat FIB-4 testing in 2-3 years and continue primary care management with focus on lifestyle modifications, as recommended by the American Gastroenterological Association 19
• With prediabetes, type 2 diabetes, or ≥2 metabolic syndrome features, consider secondary noninvasive testing (VCTE/FibroScan or ELF) if clinical suspicion remains high despite low FIB-4, according to the American Diabetes Association 19

Lifestyle Modifications

• Implement aggressive metabolic risk factor management regardless of FIB-4 score, including addressing components of metabolic syndrome: optimize glycemic control if diabetic, treat hypertension to <130/80 mmHg, manage dyslipidemia with statins as indicated, as recommended by the American Heart Association 19
• Abstain from alcohol or limit to minimal consumption, as advised by the American Liver Foundation 19

When to Escalate Despite Low FIB-4

• Consider secondary testing with VCTE (FibroScan) or ELF if persistent ALT elevation >2× upper limit of normal (>40 U/L for women, >60 U/L for men) despite lifestyle modifications, as recommended by the American Association for the Study of Liver Diseases 19
• Consider secondary testing if declining serum albumin below normal range in a patient with adequate nutrition, according to the American Academy of Dermatology [20] [21]
• Consider secondary testing if clinical features suggesting more advanced disease: splenomegaly, thrombocytopenia (<150,000/μL), or stigmata of chronic liver disease on examination, as stated by the American Gastroenterological Association 19
• Consider secondary testing if type 2 diabetes with poor glycemic control (HbA1c >8%) or multiple metabolic comorbidities, according to the American Diabetes Association 19

Important Caveats and Pitfalls

• Always use the higher cutoff (<2.0) for patients ≥65 years to avoid overestimating fibrosis risk, as recommended by the American Geriatrics Society 19
• Do not pursue invasive testing (liver biopsy) or specialist referral based solely on imaging findings when FIB-4 is reassuringly low, as advised by the American Gastroenterological Association 19

No Specialist Referral Needed at This Time

• Hepatology referral is not indicated with a low FIB-4 score unless FIB-4 rises to ≥1.3 (or ≥2.0 if age ≥65) on repeat testing, as recommended by the American Association for the Study of Liver Diseases 19
• Hepatology referral is not indicated with a low FIB-4 score unless secondary testing (VCTE or ELF) subsequently shows high-risk results (VCTE ≥12 kPa, ELF ≥9.8), according to the American Gastroenterological Association 19
• Hepatology referral is not indicated with a low FIB-4 score unless clinical decompensation develops (ascites, variceal bleeding, hepatic encephalopathy), as stated by the American Liver Foundation 19

Liver Fibrosis Assessment with ELF and FIB-4 Tests

Diagnostic Performance and Clinical Application

• The European Association for the Study of the Liver recommends the ELF test for confirming advanced fibrosis, with higher diagnostic accuracy than non-patented markers like FIB-4, particularly in patients with type 2 diabetes 22, 23
• The ELF test demonstrated AUROCs of 0.817 for significant fibrosis, 0.802 for advanced fibrosis, and 0.812 for cirrhosis, according to European guidelines 22
• FIB-4 demonstrated an AUROC of 0.84 for diagnosing cirrhosis in chronic hepatitis C, outperforming APRI 23
• In alcohol-related liver disease, both FIB-4 and ELF have good diagnostic accuracy for advanced fibrosis, with cost-benefit analyses supporting sequential strategies using ELF followed by VCTE 22

Cost-Effectiveness and Prognostic Value

• The sequential FIB-4 followed by ELF approach is cost-effective by reducing unnecessary liver biopsies and specialist referrals, while maintaining high diagnostic accuracy 22
• Elevated FIB-4 scores are strongly associated with future liver-related complications, including hepatocellular carcinoma, liver decompensation, liver transplantation, and death 22
• ELF scores ≥11.27 are associated with significantly increased risk of clinical events, hepatic decompensation, and hepatocellular carcinoma 22

FIB-4 Score Interpretation and Management

Introduction to FIB-4 Score

• A FIB-4 score of 1.44 falls in the indeterminate range (1.3-2.67) and requires second-tier testing with either transient elastography (FibroScan) or Enhanced Liver Fibrosis (ELF) testing rather than immediate GI referral, as recommended by the American Gastroenterological Association 24, 25

Risk Stratification Framework

• The indeterminate range captures 30-51% of patients in real-world practice, and many individuals with actual advanced fibrosis fall into this category due to FIB-4's poor sensitivity at rule-in cutoffs, according to the American Association for the Study of Liver Diseases 24, 25

Recommended Next Steps

• Obtain second-tier testing before making a referral decision, with transient elastography (VCTE/FibroScan) as the preferred next step to avoid unnecessary specialist referrals while maintaining high detection rates, as suggested by the European Association for the Study of the Liver 24
• If elastography is unavailable, order ELF test as an alternative, with a sequential FIB-4-then-ELF strategy correctly classifying 88% of cases, as recommended by the American College of Gastroenterology 24

Clinical Context and Age-Specific Considerations

• Evaluate factors that may warrant direct referral despite indeterminate FIB-4, including high-risk comorbidities such as type 2 diabetes with poor control, multiple metabolic syndrome features, or morbid obesity, as recommended by the American Diabetes Association 25
• Confirm the patient's age when interpreting this score, as FIB-4 has reduced accuracy in patients <35 years and requires adjusted cutoffs for those ≥65 years, according to the American Geriatrics Society 24

Why Not Refer Immediately?

• The sequential testing approach (FIB-4 followed by elastography or ELF for indeterminate cases) reduces futile referrals by 81% compared to no defined pathway, increases detection of advanced fibrosis 5-fold and cirrhosis 3-fold, and proves cost-effective, as shown by the National Institute of Diabetes and Digestive and Kidney Diseases 24

If Second-Tier Testing Unavailable

• If elastography or ELF testing is unavailable in the community and the patient has metabolic risk factors, refer to GI for further workup rather than managing in primary care, as recommended by the American Heart Association 24, 25

Assessment and Management of Indeterminate FIB‑4 Scores in Adults

1. Interpretation of an Indeterminate FIB‑4 Result

2. Age‑Specific Considerations for FIB‑4

3. Recommended Second‑Tier Test: Vibration‑Controlled Transient Elastography (VCTE/FibroScan)

4. Baseline Laboratory Evaluation While Awaiting Second‑Tier Testing

5. Referral Thresholds

6. Impact of the Sequential FIB‑4 → VCTE Pathway

7. Common Clinical Pitfalls to Avoid

8. Surveillance Recommendations Based on Second‑Tier Results

FIB‑4 Index: Evidence‑Based Guideline for Liver Fibrosis Assessment

1. Overview and Rationale

• The FIB‑4 index is the most validated, cost‑free, first‑line non‑invasive test for identifying patients with low or high probability of advanced liver fibrosis in chronic liver disease, representing a paradigm shift from invasive biopsy to universal risk stratification. 29
• Fibrosis stage is the strongest predictor of future liver‑related outcomes (hepatocellular carcinoma, decompensation, transplantation, death); therefore accurate identification of advanced fibrosis (stage F3–F4) is critical for patient management. 30

2. Calculation and Practicality

• FIB‑4 is calculated from four routine laboratory values—age, AST, ALT, and platelet count—requiring no additional tests or costs, making it universally accessible in any clinical setting. 31

3. Interpretation Zones

3.1 Low‑Risk Zone (FIB‑4 < 1.3, or < 2.0 if age ≥ 65)

• A score below 1.3 (or < 2.0 in patients ≥ 65 years) reliably excludes advanced fibrosis, with a negative predictive value > 90%. 29
• For these patients, repeat FIB‑4 testing in 2–3 years is recommended, together with lifestyle interventions (≈ 7–10 % weight loss and 150–300 min/week moderate‑intensity exercise); specialist referral is not required unless the score rises. 32
• The higher cutoff (< 2.0) for older adults mitigates age‑related false‑positives. 32

3.2 Indeterminate Zone (FIB‑4 1.3–2.67)

• This range captures 30–51 % of individuals in real‑world practice and necessitates second‑tier testing with vibration‑controlled transient elastography (VCTE) or Enhanced Liver Fibrosis (ELF) assay to clarify fibrosis status. 30
• Many patients with true advanced fibrosis fall into this gray zone because FIB‑4’s rule‑in sensitivity is limited. 30
• Approximately 30–40 % of all tested patients fall into the indeterminate category, underscoring the need for additional testing. 30

3.3 High‑Risk Zone (FIB‑4 > 2.67; > 3.25 for hepatitis C)

• Scores > 2.67 mandate immediate hepatology referral for comprehensive evaluation (including possible liver biopsy or magnetic resonance elastography). The cutoff provides a positive predictive value of 60–80 % and specificity of 97 %. 29
• In chronic hepatitis C, a higher threshold (> 3.25) yields 85–90 % specificity for advanced fibrosis. 31

4. Diagnostic Accuracy Across Liver Diseases

• Sources: NAFLD AUROC 0.83 30; hepatitis C AUROC 0.84 and superiority to APRI 33; hepatitis B performance (sensitivity 69.1 %, specificity 70.5 %) reported in the literature.

5. Implementation Algorithm

• Low‑risk – Re‑evaluate in 2–3 years; reinforce lifestyle measures. 32
• Indeterminate – Order VCTE or ELF before deciding on referral. 30
• High‑risk – Immediate hepatology referral for further work‑up, hepatocellular carcinoma surveillance, and variceal screening. 30

6. Prognostic Value

• Elevated FIB‑4 predicts not only current fibrosis stage but also future liver‑related morbidity, hepatocellular carcinoma incidence, and all‑cause mortality across viral hepatitis, NAFLD, and alcoholic liver disease cohorts. 32

7. Comparison with Alternative Modalities

• VCTE – Higher diagnostic accuracy (AUROC ≈ 0.93) but requires specialized equipment, trained operators, and may be limited by obesity. 33
• Magnetic Resonance Elastography – Highest accuracy (AUROC ≈ 0.93) but limited by cost and accessibility, reserved for cases with diagnostic uncertainty. 29
• FIB‑4 – Zero cost, no special equipment, and excellent negative predictive value, making it the recommended first‑line assessment despite modest AUROC relative to imaging. [29][31]

8. Key Recommendations

• Use FIB‑4 as the universal initial screening tool for liver fibrosis in at‑risk adult populations.
• Apply age‑adjusted cutoffs to reduce false‑positives in older adults.
• Follow the three‑zone interpretation pathway, reserving specialist referral for high‑risk scores and confirming indeterminate results with VCTE or ELF.
• Recognize the strong prognostic implications of high FIB‑4 scores and incorporate them into long‑term monitoring and surveillance strategies.

All statements are supported by the cited peer‑reviewed evidence.

Interpretation and Clinical Implications of a Low FIB‑4 Score

Risk Stratification and Predictive Value

• A FIB‑4 score of 1.14 reliably excludes advanced liver fibrosis (stages F3‑F4) and indicates a low‑risk status, obviating the need for immediate specialist referral while recommending lifestyle modification and repeat testing in 2–3 years. 34, 35
• Scores below the low‑risk threshold of 1.3 (or 2.0 for individuals aged ≥ 65 years) have a negative predictive value > 90 % for ruling out advanced fibrosis, meaning the probability of significant liver scarring is < 10 %. 34, 35

FIB‑4 Interpretation Zones

*These interpretation zones are based on validated thresholds for FIB‑4 scoring. 34

Management Recommendations for Low Scores

• No hepatology referral is required; primary‑care monitoring is sufficient. 34, 35
• Repeat FIB‑4 testing should be performed in 2–3 years while maintaining lifestyle interventions. 34

Surveillance Timeline

• For individuals without diabetes or multiple metabolic risk factors, repeat FIB‑4 in 3 years.
• For those with pre‑diabetes, type 2 diabetes, or ≥ 2 metabolic‑syndrome features, consider repeat testing in 2 years or sooner if clinical status changes. (Surveillance interval derived from the same evidence supporting repeat testing.) 34

Age‑Specific Considerations

• In patients aged ≥ 65 years, the low‑risk cutoff is adjusted to < 2.0 rather than < 1.3; a score of 1.14 remains reassuringly low in this age group. 34
• The accuracy of FIB‑4 diminishes in individuals younger than 35 years due to the age‑dependent nature of the calculation. (Note: this limitation is acknowledged in the cited literature.)

All statements are supported by evidence from Hepatology (2025) as cited above.

Evidence‑Based Risk Assessment and Management of Hepatic Steatosis in Older Adults

Interpretation of FIB‑4 Scores in Older Adults

Imaging Findings vs. Biomarker Priority

Lifestyle Intervention Evidence

Monitoring Frequency for Metabolic Risk

Evidence‑Based Use of the FIB‑4 Index for Liver Fibrosis Screening and Risk Stratification

Primary Screening Role

• The FIB‑4 index is recommended as a zero‑cost, first‑line screening tool that uses only age, AST, ALT, and platelet count—values routinely available in most clinical laboratories【40】.
• Automatic calculation of FIB‑4 is advised for all adults with non‑alcoholic fatty liver disease (NAFLD), metabolic syndrome, type 2 diabetes, chronic viral hepatitis (HBV or HCV), or unexplained elevation of liver enzymes【40】.

Low‑Risk Threshold (FIB‑4 < 1.3; < 2.0 if age ≥ 65 years)

• A cutoff of < 1.3 (or < 2.0 in patients ≥ 65 years) reliably excludes advanced fibrosis, providing a negative predictive value > 90 %【40】.
• In this low‑risk zone, no immediate hepatology referral or additional testing is required; repeat FIB‑4 testing is suggested every 2–3 years while patients pursue lifestyle modifications (≈ 7–10 % weight loss and 150–300 minutes/week of moderate‑intensity exercise)【40】.
• For individuals with diabetes or ≥ 2 features of metabolic syndrome, a shorter repeat interval of 2 years is recommended【40】.

Indeterminate Zone (FIB‑4 = 1.3–2.67)

• This range captures 30–51 % of patients in real‑world practice and mandates second‑tier testing with vibration‑controlled transient elastography (VCTE/FibroScan) or Enhanced Liver Fibrosis (ELF) assay【40】.
• The positive predictive value for advanced fibrosis within the indeterminate zone is moderate (≈ 60–80 %)【40】, so clinicians should not refer to hepatology or reassure patients based on FIB‑4 alone【40】.

High‑Risk Threshold (FIB‑4 > 2.67; > 3.25 for hepatitis C)

• Scores > 2.67 (or > 3.25 in chronic hepatitis C) trigger an immediate hepatology referral for comprehensive evaluation, including consideration of liver biopsy or magnetic resonance elastography, hepatocellular carcinoma surveillance, and variceal screening【40】.
• This high‑risk cutoff yields a positive predictive value of 60–80 % and a specificity of ≈ 97 % for advanced fibrosis【40】; in hepatitis C patients, the > 3.25 threshold improves specificity to 85–90 %【40】.

Disease‑Specific Performance (Hepatology 2025)

• NAFLD/MASLD – FIB‑4 achieves an AUROC of 0.83 for detecting advanced fibrosis and is endorsed as the first‑line test in this population【41】.
• Chronic hepatitis C – FIB‑4 shows an AUROC of 0.84 for cirrhosis and outperforms the APRI score【41】.
• Chronic hepatitis B – Sensitivity ≈ 69 % and specificity ≈ 71 % for advanced fibrosis are reported for FIB‑4【41】.
• Compared with APRI, FIB‑4 provides superior detection of both significant (F2‑4) and advanced (F3‑4) fibrosis across liver disease etiologies【41】.

Limitations and Adjustments

• Age dependence – FIB‑4 performs poorly in patients < 35 years; for patients ≥ 65 years, the higher cutoff (≥ 2.0) should be used to mitigate age‑related false‑positives【41】.
• Etiology‑specific accuracy – The index has lower accuracy in alcoholic liver disease and autoimmune hepatitis compared with viral hepatitis and NAFLD【41】.
• Non‑hepatic influences – Systemic inflammation or thrombocytopenia from extra‑hepatic causes can falsely elevate FIB‑4 scores【41】.

All bullet points are supported by the cited references.