Liver Elastography: Interpretation of kPa Values and METAVIR Fibrosis Stages
METAVIR Staging System
According to Diagnostic Ultrasound: Abdomen & Pelvis (2022), the METAVIR system classifies liver fibrosis as follows:
| Stage | Description |
|---|---|
| F0 | No fibrosis |
| F1 | Perisinusoidal or portal fibrosis |
| F2 | Perisinusoidal + portal or periportal fibrosis |
| F3 | Septal or bridging fibrosis |
| F4 | Cirrhosis |
Significant fibrosis is considered F2 and above, advanced fibrosis is F3 and above. Liver biopsy remains the current gold standard for staging, but it is invasive and subject to sampling errors. Ultrasound shear-wave elastography (SWE) is a non-invasive method for assessing fibrosis.
Interpretation of kPa Values (SRU Consensus)
According to the consensus recommendations of the Society of Radiologists in Ultrasound (as presented in Diagnostic Ultrasound: Abdomen & Pelvis, 2022):
| Value | Interpretation |
|---|---|
| <5 kPa (1.3 m/s) | High likelihood of normal |
| 5–9 kPa (1.3–1.7 m/s) | In the absence of other clinical signs, excludes compensated advanced chronic liver disease (cACLD); if signs are present, a confirmatory test may be needed |
| 9–13 kPa (1.7–2.1 m/s) | Suggests cACLD, requires additional confirmatory testing |
| 13–17 kPa (2.1–2.4 m/s) | Highly suspicious for cACLD |
Normal Values and Cut-offs by Technology
According to the EFSUMB Course Book (2018), in transient elastography (TE), liver stiffness values in individuals without liver pathology range from 4.3 to 5.3 kPa, with higher values observed in men compared to women.
For differentiating F0–1 from F2–4 in TE, a cut-off of 7.5 kPa is provided with a sensitivity of 67%, specificity of 87%, PPV of 86%, NPV of 68%, and diagnostic accuracy of 76%. In other studies, the cut-off for distinguishing F0–1 and F2–4 ranged from 6.8 to 7.3 kPa.
For 2D-SWE (SSI), one study provided cut-offs: for F>3 — 8.7 kPa (AUROC=0.98), for F4 — 10.4 kPa (AUROC=0.98). In another study, AUROC values for 2D-SWE.SSI were 0.948 for F≥2, 0.962 for F≥3, and 0.968 for F≥4.
Staging Characteristics
According to the EFSUMB Course Book (2018), in chronic hepatitis B, liver stiffness values significantly overlap between adjacent fibrosis stages, especially at lower stages; however, the method is very effective in identifying patients with F≥2 and F4.
Frequently asked questions
What kPa value corresponds to normal?
According to the SRU consensus, <5 kPa (1.3 m/s) indicates a high likelihood of normal. In transient elastography, the normal range for individuals without liver pathology is 4.3–5.3 kPa (EFSUMB, 2018).
What cut-off separates significant fibrosis (F2–4) from F0–1?
In TE, a cut-off of 7.5 kPa is provided (sensitivity 67%, specificity 87%); in other studies, the range is 6.8–7.3 kPa (EFSUMB Course Book, 2018).
What is considered significant and advanced fibrosis according to METAVIR?
Significant fibrosis is F2 and above, advanced fibrosis is F3 and above (Diagnostic Ultrasound, 2022).
At what values can cACLD be excluded?
5–9 kPa (1.3–1.7 m/s) in the absence of other clinical signs excludes compensated advanced chronic liver disease; if signs are present, a confirmatory test may be needed (SRU consensus).
Is biopsy still the gold standard?
Yes, liver biopsy is the current gold standard for fibrosis staging, but it is invasive and subject to sampling errors; SWE is a non-invasive alternative (Diagnostic Ultrasound, 2022).