Healthcare & Clinical Calculations
Forns Index Non-Invasive Liver Fibrosis Calculator (Platelets, GGT, Cholesterol)
Calculate Xavier Forns’s logarithmic hepatic fibrosis index 7.811 - 3.131*LN(Platelets_10^9/L) + 0.781*LN(GGT_IU/L) + 3.467*LN(Age) - 0.014*Cholesterol_mg/dL (< 4.2 rules out F2–F4 fibrosis with 96% NPV; > 6.9 rules in).
Combine hypersplenism platelets, biliary GGT, and declining hepatic cholesterol synthesis!
Even when transaminases (AST/ALT) fluctuate or normalize in chronic viral and metabolic hepatitis, three orthogonal physiological markers track progressive portal fibrosis: falling Platelet count (10^9/L, splenic sequestration + lower thrombopoietin), rising Gamma-Glutamyl Transferase GGT (IU/L), and falling hepatic Total Cholesterol synthesis (mg/dL)! Xavier Forns et al. (Hepatology 2002) combined these with patient Age (years) into the continuous Forns Index: Forns = 7.811 - 3.131 * LN(Platelets_10_9L) + 0.781 * LN(GGT_IUL) + 3.467 * LN(Age_yr) - 0.014 * Cholesterol_mgdL!
Dual Forns cutoffs spare nearly half of patients from invasive biopsy: Forns < 4.2 excludes significant Metavir F2–F4 fibrosis with 96% Negative Predictive Value, 4.2–6.9 is Indeterminate (proceed to FibroScan elastography), and Forns > 6.9 rules in significant fibrosis with ~66–79% Positive Predictive Value! Compare Platelets = 135 x 10^9/L, GGT = 92 IU/L, Age = 54, Cholesterol = 175 mg/dL -> Forns = 7.36 (> 6.9 Significant Fibrosis) against healthy Platelets = 260, GGT = 28, Age = 36, Cholesterol = 195 -> Forns = 2.70 (< 4.2 Fibrosis Excluded)!
| Clinical Lab Profile (Plt 10^9/L, GGT IU/L, Chol mg/dL) | Forns Index Value | Validated Cutoff Zone | Hepatology Action |
|---|---|---|---|
| Healthy Liver (Plt 260, GGT 28, Age 36, Chol 195) | 2.70 | < 4.20 (96% NPV) | Significant F2–F4 Fibrosis Excluded |
| Gray Zone (4.20 to 6.90) | 4.20–6.90 | Indeterminate Zone | Perform VCTE / Shear-Wave Elastography |
| Fibrotic Profile (Plt 135, GGT 92, Age 54, Chol 175) | 7.36 | > 6.90 (Rule-In) | High Likelihood of Significant Fibrosis |
Continuous Logarithmic Forns Hepatic Fibrosis Index
Evaluates 7.811 - 3.131*LN(B2) + 0.781*LN(B3) + 3.467*LN(B4) - 0.014*B5 (note Platelets in 10^9/L, e.g., 135 NOT 135,000!).
=IF(OR(B2 <= 0, B3 <= 0, B4 <= 0, B5 <= 0), "Invalid Forns Lab Input", ROUND(7.811 - 3.131 * LN(B2) + 0.781 * LN(B3) + 3.467 * LN(B4) - 0.014 * B5, 2))Forns Dual-Cutoff Fibrosis Stratification (< 4.2 vs. > 6.9)
Classifies Forns < 4.2 (Rule-Out), 4.2–6.9 (Indeterminate), and > 6.9 (Rule-In Significant Fibrosis).
=IF(OR(B2 <= 0, B3 <= 0, B4 <= 0, B5 <= 0), "Invalid Forns Lab Input", IF((7.811 - 3.131 * LN(B2) + 0.781 * LN(B3) + 3.467 * LN(B4) - 0.014 * B5) > 6.9, "High Fibrosis Probability (Forns > 6.9) — Significant F2-F4 Fibrosis Likely", IF((7.811 - 3.131 * LN(B2) + 0.781 * LN(B3) + 3.467 * LN(B4) - 0.014 * B5) < 4.2, "Low Fibrosis Probability (Forns < 4.2: 96% NPV) — Significant Fibrosis Excluded", "Indeterminate Forns Zone (4.2-6.9) — Confirm With Elastography")))Try the example
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