Liver Stiffness Norms in Elastography: kPa Thresholds by Fibrosis Stages F0–F4 (METAVIR)
Fibrosis Staging by METAVIR
The METAVIR system identifies stages: F0 — no fibrosis; F1 — peri-sinusoidal or portal fibrosis; F2 — peri-sinusoidal + 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 is invasive and subject to sampling error (Diagnostic Ultrasound: Abdomen & Pelvis, 2022).
Thresholds by Society of Radiologists in Ultrasound Consensus
Shear wave ultrasound elastography is a non-invasive method for assessing liver fibrosis. According to the consensus recommendations of the Society of Radiologists in Ultrasound (Diagnostic Ultrasound: Abdomen & Pelvis, 2022):
| Stiffness, kPa (m/s) | Interpretation |
|---|---|
| <5 kPa (1.3 m/s) | High likelihood of normality |
| 5–9 kPa (1.3–1.7 m/s) | In the absence of clinical signs, excludes cACLD; with known clinical signs, a confirmatory test may be required |
| 9–13 kPa (1.7–2.1 m/s) | Suggests cACLD, confirmation required |
| 13–17 kPa (2.1–2.4 m/s) | Highly suspicious for cACLD |
Normal Values by Technology
According to the EFSUMB Course Book (Sporea et al., 2018), in transient elastography (TE), stiffness values in individuals without liver pathology are 4.3–5.3 kPa, with higher values in men than in women.
According to WFUMB (Ferraioli et al., 2015): in the absence of fibrosis (F0), the shear wave speed is 1.0 m/s, elasticity is 3 kPa; in cirrhosis (F4), the speed is 3.0 m/s, elasticity is 27 kPa. The elasticity modulus is expressed as E = 3ρVₛ², where Vₛ is the shear wave speed, ρ is the tissue density (close to 1000 kg/m³): the stiffer the tissue, the faster the wave propagates.
Thresholds for Chronic Hepatitis C by Methods
According to the EFSUMB Course Book (Sporea et al., 2018), the following thresholds are provided for chronic hepatitis C:
| Method | Threshold, kPa | Stage |
|---|---|---|
| TE | 7.5 (range 6.8–7.3 in other studies) | F0–1 vs F2–4 |
| ElastPQ | 6.43 / 9.54 / 11.34 | significant fibrosis / advanced fibrosis / cirrhosis |
| 2D-SWE (SSI, Aixplorer) | 7.1 (AUROC 0.92) | F≥2 |
| 2D-SWE (SSI, Aixplorer) | 8.7 (AUROC 0.98) | F≥3 |
| 2D-SWE (SSI, Aixplorer) | 10.4 (AUROC 0.98) | F4 |
For the TE threshold of 7.5 kPa (F0–1 vs F2–4), sensitivity is reported at 67%, specificity at 87%, PPV at 86%, NPV at 68%, and diagnostic accuracy at 76% (Sporea et al., 2018).
The provided technology-specific thresholds (ElastPQ, 2D-SWE) are predominantly validated in cohorts of patients with chronic hepatitis C. The complete system of threshold value adjustments by etiology is not detailed in the provided fragments [clarification needed].
Frequently asked questions
What stiffness value is highly likely to be normal?
According to the Society of Radiologists in Ultrasound consensus, values <5 kPa (1.3 m/s) are highly likely to be normal (Diagnostic Ultrasound, 2022).
What normal values does transient elastography provide for healthy individuals?
According to the EFSUMB Course Book (2018), TE values in individuals without liver pathology are 4.3–5.3 kPa; values are higher in men than in women.
What are the stiffness values for F0 and F4 according to WFUMB?
For F0, the shear wave speed is 1.0 m/s and elasticity is 3 kPa; for F4 (cirrhosis), the speed is 3.0 m/s and elasticity is 27 kPa (Ferraioli et al., 2015).
What TE threshold differentiates insignificant from significant fibrosis?
The threshold of 7.5 kPa differentiates F0–1 from F2–4 with a sensitivity of 67%, specificity of 87%, and accuracy of 76%; other studies provide a range of 6.8–7.3 kPa (Sporea et al., 2018).
Do thresholds differ for different SWE technologies?
Yes. For 2D-SWE (SSI): F≥2 — 7.1 kPa, F≥3 — 8.7 kPa, F4 — 10.4 kPa. For ElastPQ: significant fibrosis 6.43, advanced fibrosis 9.54, cirrhosis 11.34 kPa (Sporea et al., 2018).