Liver viscosity: pathological significance and interest for the assessment of MASLD severity in clinical practice

The non-invasive diagnosis of metabolic dysfunction-associated steatohepatitis (MASH) is a critical unmet need. Liver viscosity is a new ultrasound measurement based on 2D-Shear Wave Elastography (2D-SWE). We aimed to characterize the association between liver viscosity and histologic component, and to determine whether this new parameter can improve the non-invasive diagnosis of MASH.

Two hundred seventy-five patients undergoing liver biopsy for suspected MASLD were included and had 2D-SWE with liver viscosity measurements. Patients were enrolled in Angers University Hospital (derivation set, n = 183) and Besançon University Hospital (validation set, n = 92) centers. MASH was defined on liver biopsy as the presence of steatosis with lobular inflammation and ballooning.

Independent predictors of MASH in the derivation set (BMI, gender, liver viscosity) were combined into the MASH score. The AUROC of the MASH score was 0.85 [95% CI: 0.79-0.92] in the derivation set and 0.82 [95% CI: 0.73-0.92] in the validation set. The rule-out (≤ 0.578) and rule-in (≥ 0.863) thresholds determined in the derivation set provided, respectively, 84% sensitivity and 96% specificity in the validation set. The AUROC of 2D-SWE for significant fibrosis F ≥ 2 was 0.82 [95% CI: 0.77-0.88]. The MASH score was combined with 2D-SWE to diagnose fibrotic MASH, which is the indication for pharmacological therapy. The AUROC of the combination was 0.81 [95% CI: 0.74-0.87] in the derivation set and 0.78 [95% CI: 0.69-0.87] in the validation set.

The ultrasound-based MASH score accurately diagnoses MASH. Combined with 2D-SWE available in the same device, it accurately identifies MASLD patients who require pharmacological therapy.

Question The transition from MASLD to MASH is critical, yet no simple non-invasive diagnostic method currently exists for accurately identifying MASH patients. Findings Liver viscosity measured by 2D-SWE, combined with BMI and gender, provides a score (MASH score) that accurately diagnoses MASH. Clinical relevance This ultrasound-based MASH score offers a practical and widely accessible tool to identify patients with MASH or fibrotic MASH requiring follow-up and treatment, improving management of MASH.