Positive predictive value of LI-RADS US-3 observations: multivariable analysis of clinical and imaging features

Purpose To determine how clinical and imaging features affect the positive predictive values (PPV) of US-3 observations. Methods In this retrospective study, 10,546 adult patients who were high risk for hepatocellular carcinoma (HCC) from 2017 to 2021 underwent ultrasound screening/surveillance. Of these, 225 adult patients (100 women, 125 men) with an US-3 observation underwent diagnostic characterization with multiphasic CT (93; 41%), MRI (130; 58%), or contrast-enhanced ultrasound (2; 1%). US-3 observations included focal observations ≥ 10 mm in 216 patients and new venous thrombi in 9 patients. PPV with 95% confidence intervals were calculated using diagnostic characterization as the reference standard. Multivariable analysis of clinical and imaging features was performed to determine the strongest associations with cancer. Results Overall PPV for an US-3 observation was 33% (27–39%) for at least intermediate probability of cancer (≥ LR-3) and 15% (10–20%) for at least probable cancer (≥ LR-4). At multivariable analysis, cirrhosis had the strongest effect size for at least probable cancer ( p < 0.001; odds ratio OR 20.4), followed by observation size ( p < 0.001; OR 2.65) and age ( p = 0.004; OR 1.05). Alpha-fetoprotein, visualization score, and observation echogenicity were not statistically significant associations. Modality (MRI versus CT) did not affect PPV. Due to the large effect of cirrhosis, PPV was then stratified by the presence ( n = 116; 52%) or absence ( n = 109; 48%) of cirrhosis. For at least probable cancer (≥ LR-4), PPV increased from 4% (0–7%; non-cirrhotic) to 26% (18–34%; p < 0.001; cirrhosis). Conclusion Cirrhosis most strongly affects PPV of US-3 observations for at least probable cancer at diagnostic characterization among high-risk patients, increasing to 1 in 4 among cirrhotic patients from 1 in 25 among non-cirrhotic patients. Graphical Abstract