Feasibility of non-enhanced CT for assessing longitudinal changes in hepatic steatosis

To evaluate the feasibility of computed tomography (CT) in the assessment of the change in hepatic steatosis (HS) in longitudinal follow-up by employing pathological HS as the reference standard. We retrospectively evaluated 38 living liver donor candidates (27 men and 11 women; mean age, 29.5 years) who underwent liver biopsy twice and had liver CT scans within 1 week of each biopsy. Four readers independently calculated CT_L-S index by subtracting spleen attenuation from liver attenuation on non-enhanced CT images. The changes in pathological HS (DHS) and CT_L-S (DCT_L-S) between the 1st and 2nd examinations were assessed. The correlation between DHS and DCT_L-S was assessed using the linear regression analysis. Inter-observer measurement error for DCT_L-S among the 4 readers was assessed using the repeatability coefficient. DCT_L-S showed a significant correlation with DHS in all readers (r = 0.571–0.65, P < .001). The inter-observer measurement error for DCT_L-S was ±8.9. The DCT_L-S values beyond the measurement error were associated with a consistent change in HS in 83.3% (13/15) to 100% (15/15), with sensitivities of 47.8 to 79.9% and specificities of 86.7 to 100% for detecting an absolute change of ≥10% in HS among the 4 readers. However, DCT_L-S values within the measurement error were associated with a consistent change in HS in 43.5% (8/19) to 61.5% (16/26). The change in CT_L-S roughly reflects the change in HS during longitudinal follow-up. A small change in CT_L-S should not be considered meaningful, while a larger change in CT_L-S beyond the measurement error strongly indicates a true change in HS. Abbreviations: ALT = alanine aminotransferase, AST = aspartate aminotransferase, BMI = body mass index, CT = computed tomography, HS = hepatic steatosis, HSI = hepatic steatosis index, HU = Hounsfield unit, ICC = intraclass correlation coefficient, MR = magnetic resonance, ROI = region-of-interest, US = ultrasonography.