• Unenhanced CT liver attenuation is highly specific for diagnosing moderate/severe hepatic steatosis. • Unenhanced CT can identify large cohorts for epidemiological studies of incidental steatosis. • Unenhanced CT is not, however, effective for population screening for hepatic steatosis.

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OBJECTIVE The objective of this study was to evaluate changes in liver fat content over time in asymptomatic adults and to investigate the factors that may influence these changes. MATERIALS AND METHODS Liver attenuation on unenhanced CT images of 1022 asymptomatic adults (556 women and 466 men; mean age at the time of the index CT examination, 56.7 years) was retrospectively measured on initial and surveillance CT colonography screening examinations (mean [± SD] interval, 5.5 ± 0.8 years). Changes in liver attenuation (expressed as Hounsfield units) were assessed according to various factors, including body mass index (BMI), age, and sex. RESULTS Mean liver attenuation was 60.3 HU on the index CT scan and 58.4 HU on the 5-year follow-up CT scan (p < 0.0001). Changes in liver attenuation greater than 10 HU, 5–10 HU, and less than 5 HU were observed in 187 (18%), 212 (21%), and 623 (61%) individuals, respectively. Changes in attenuation greater than 10 HU were negative (i.e., fattier liver) in 130 of 187 individuals (70%) and were more likely to be associated with an increase in BMI (83 of 130 individuals [64%] vs 19 of 57 individuals [33%]; p < 0.0001). For changes in attenuation of 5 HU or more, negative (steatotic) changes outnumbered positive changes, occurring in 258 of 1022 individuals (25%) versus 141 of 1022 individuals (14%) (p < 0.0001). Changes in BMI were negatively correlated with changes in attenuation (p = 0.015). There was no statistically significant correlation between changes in attenuation and either age or sex. An improved lipid profile and the use of a lipid-lowering medication regimen correlated with an interval decrease in liver attenuation. CONCLUSION Changes in liver attenuation over time, reflecting temporal changes in fat content, were quite variable in this asymptomatic adult population and were only partially explained by the factors examined. These observations may provide early insight into the natural history of incidental hepatic steatosis in asymptomatic adults.

Purpose: To identify sequence variants of the ataxia telangiectasia mutated (ATM) gene and establish their prevalence rate among American Indian (AI) as compared with non-AI cancer patients.Materials and Methods: DNA was isolated from blood samples collected from 100 AI and 100 non-AI cancer patients undergoing radiation therapy, and a blinded assessment of the ATM sequence was conducted. Quantitative PCR assessment of copy number for each exon was also performed. The main outcome measure was the prevalence of ATM variants in the two patient populations.Results: No statistically significant differences for total prevalence of ATM variants among AI and non-AI patients were found. Of the 25 variants identified, 5 variants had a prevalence of >2%, of which 4 occurred at a rate of >5% in one or both groups. The prevalence of these four variants could meaningfully be compared between the two groups. The only statistically significant difference among the groups was the c.4138C > T variant which is predicted not to affect protein function, seen in 8% of AI versus 0% of non-AI patients (P = 0.007). No exonic copy number changes were found in these patients.Conclusion: This study is the first to determine the prevalence of ATM variants in AIs.