Ultrasound-based steatosis grading system using 2D-attenuation imaging: an individual patient data meta-analysis with external validation

Background and rationale: Non-invasive tools assessing steatosis, such as ultrasonography-based 2D-attenuation imaging (ATI), are needed to tackle the worldwide burden of steatotic liver disease. This one-stage individual patient data (IPD) meta-analysis aimed to create an ATI-based steatosis grading system. Main Results: A systematic review (EMBASE+MEDLINE, 2018-2022) identified studies, including patients with histologically or MRI-PDFF-verified ATI for grading steatosis (S0 to S3). One-stage IPD meta-analyses were conducted using generalized mixed models with a random study-specific intercept. Created ATI-based steatosis grading system (aS0 to aS3) was externally validated on a prospective cohort of patients with type 2 diabetes and metabolic dysfunction-associated steatotic liver disease (MASLD; n=174, histologically and MRI-PDFF verified steatosis). Eleven enrolled studies included 1374 patients, classified into S0, S1, S2, and S3 in 45.4%, 35.0%, 9.3%, and 10.3% of the cases. ATI was correlated with histological steatosis (r=0.60; 95%CI:0.52,0.67; p<0.001), and MRI-PDFF (r=0.70; 95%CI:0.66,0.73; p<0.001) but not with liver stiffness (r=0.03; 95%CI:-0.04,0.11, p=0.343). Steatosis grade was an independent factor associated with ATI (Coefficient: 0.24; 95%CI [0.22, 0.26]; p<0.001). ATI marginal means within S0, S1, S2, and S3 subpopulations were 0.59 (95%CI [0.58, 0.61]), 0.69 (95%CI [0.67, 0.71]), 0.78 95%CI [0.76, 0.81] and 0.85 95%CI [0.83, 0.88] dB/cm/MHz; all contrasts between grades significant (p<.0001). Three ATI thresholds were calibrated to create a new ATI-based steatosis grading system (aS0 to aS3, cut-offs: 0.66, 0.73, and 0.81 dB/cm/MHz). Its external validation showed Obuchowski measures of 0.84 ±0.02 and 0.82±0.02 with histologically- and MRI-PDFF-based references. Conclusions: ATI is a reliable, non-invasive marker of steatosis. This validated ATI-based steatosis grading system could be valuable in assessing MASLD patients.