Radiological measures of hepatic triacylglycerol accumulation
| Modality/technique | Commercial | Variables | AUROC | Sensitivity (Se) and specificity (Sp) | Comments | Primary reference |
|---|---|---|---|---|---|---|
| Routine ultrasound scanning | No | Steatosis appears as diffuse increased echogenicity | N/A | Se 0.60–0.94, Sp 0.66–0.95 | Operator dependent interobserver variation. Acceptable sensitivity if steatosis >30%. Not quantitative | Reviewed66 |
| Ultrasound Fatty Liver Indicator | No | Scoring system ranging 2–8 based on intensity of liver/kidney contrast, posterior attenuation of ultrasound beam, vessel blurring, difficult visualisation of gallbladder wall, difficult visualisation of the diaphragm and areas of focal sparing. | 0.796 | Threshold ≥2 suggests NAFLD. Threshold ≥4 predicts NASH (PPV 94%, NPV 46%) | 67 | |
| Zardi's Ultrasound score | No | Weighted sum of echo amplitude attenuation (scored 0–2) and presence/absence of focal fat sparing | Threshold ≥1: Se 0.92, Sp 0.75 | 68 | ||
| Controlled attenuation parameter | Yes | A proprietary technique that complements Fibroscan transient elastography | Steatosis >10%: 0.79–0.80; Steatosis >33%: 0.76–0.86; Steatosis >66%: 0.70–0.88 | Formal evaluation with histological correlation in NAFLD is needed | 69 70 | |
| Routine CT | Three different radiological measures, all based on liver attenuation measured in HU | Reviewed66 | ||||
| No | Liver parenchymal attenuation (CTLP): normal range 50–57 HU | Threshold CTLP <40 HU: Se 0.52, Sp 1 | ||||
| Liver–spleen attenuation difference (CTL–S): normal range 8–10 HU | Threshold CTL–S >10 HU: Se 0.60, Sp 1 | |||||
| Liver–spleen attenuation ratio (CTL/S): normal range >1.1 | Threshold CTL/S >1.1: Se 0.82, Sp 1 | |||||
| Routine MRI | No | Severity of hepatic steatosis assessed by MRI through chemical shift imaging | Better correlation than ultrasound for microscopic fat content (r=0.77, p<0.001 vs r=0.41, p<0.05). In macrovesicular steatosis, MRI and ultrasound both correlate well with microscopic fat content (r=0.92, p<0.001 vs r=0.90, p<0.001) | Superior to ultrasound in detecting and quantifying minor degrees of fatty infiltration in the liver | 71 | |
AUROC, area under the receiver operating characteristic curve; HU, Hounsfield units; NAFLD, non-alcoholic fatty liver disease; NASH, non-alcoholic steatohepatitis; NPV, negative predictive value; PPV, positive predictive value.