Optimal thresholds for ultrasound attenuation parameter in the evaluation of hepatic steatosis severity: evidence from a cohort of patients with biopsy-proven fatty liver disease

Objective: FibroTouch is a newly developed device to assess ultrasound attenuation parameter (UAP) and liver stiffness measurement to quantify hepatic steatosis and fibrosis, respectively. However, there is currently a lack of defined thresholds of UAP to diagnose different stages of hepatic steatosis. We aimed to assess the optimal thresholds of UAP for hepatic steatosis in individuals with biopsy-proven fatty liver disease (FLD).

Methods: We enrolled 497 adults with FLD undergoing FibroTouch and liver biopsy. Area under the receiver operating characteristic curve (AUROC) was performed to calculate the performance of UAP in staging hepatic steatosis. Hepatic steatosis >33% was defined as significant steatosis. We determined the optimal cutoff values of UAP and the sensitivity or specificity higher than 90%. Sensitivity, specificity, positive predictive value and negative predictive value were subsequently calculated.

Results: The median UAP for the enrolled patients was 308 dB/m. Multivariable logistic regression analysis showed that UAP was associated with significant steatosis [adjusted-odds ratio 1.05, 95% confidence interval (CI), 1.02-1.09; P = 0.001]. The AUROCs for S ≥ 1, S ≥ 2 and S = 3 were 0.88 (95% CI, 0.84-0.91), 0.77 (95% CI, 0.73-0.81), and 0.70 (95% CI, 0.63-0.77), respectively. The optimal UAP cutoffs were 295 dB/m for S ≥ 1, 314 dB/m for S ≥ 2, and 324 dB/m for S = 3. Almost identical results were observed in the subgroup of patients with biopsy-confirmed nonalcoholic fatty liver disease (n = 435).

Conclusion: We found that the AUROC values of UAP by FibroTouch were ranging from 0.70 to 0.88 for assessing hepatic steatosis severity. These UAP cutoffs could be applicable for clinical use.