Controlled attenuation parameter for the diagnosis of steatosis in non‐alcoholic fatty liver disease

Abstract

Background and Aim: Controlled attenuation parameter (CAP) evaluated with transient elastography (FibroScan) is a recent method for non-invasive assessment of steatosis. Its usefulness in non-alcoholic fatty liver disease (NAFLD) is unknown. We prospectively investigated the performance of CAP for the diagnosis of steatosis in NAFLD, factors associated with discordances between CAP and steatosis grades, and relationships between CAP and clinical or biological parameters. Methods: All CAP examinations performed in NAFLD patients with a liver biopsy performed within 1 week of CAP measurement were included. Liver biopsies were assessed for activity and fibrosis stage, NAFLD activity score, and steatosis graded as follows: S0, steatosis < 5%; S1, 5-33%; S2, 34-66%; S3, >66%. Results: Two hundred sixty-one patients (59% male, age 56 years) from two ethnic groups were included. No patient had steatosis < 5%. The area under the receiver-operating characteristics curve of CAP for steatosis ≥S2 and S3 was 0.80 and 0.66, respectively. At a cutoff value of 310 dB/m, the sensitivity, specificity, and positive and negative predictive values for ≥S2 steatosis were 79%, 71%, 86%, and 71%, respectively. Discordance of at least one grade between CAP and steatosis was observed in 81 patients. By multivariate analysis, only steatosis S2S3 was associated with no discordance. By multivariate analysis, only BMI ≥ 30 kg/m 2 was significantly associated with CAP > 310 dB/m. Conclusion: The association of CAP with steatosis, especially in patients with nonalcoholic steatohepatitis, and with elevated BMI could be useful for the diagnosis and follow-up of NAFLD patients.

Imaging-Based Assessment of Steatosis, Inflammation and Fibrosis in NAFLD

“…Significantly higher CAP values were seen in patients with S2/S3 steatosis compared to S1 (333 versus 285 dB/m; p < 0.001), and the AUROC of CAP to detect ≥ S2 and S3 was 0.8 and 0.66, respectively [12]. The optimal CAP cut-off for ≥ S2 disease was 310 dB/m [12], which provided a correct assessment of S2/S3 in 86% of the cohort [12]. Discordance of at least one grade between CAP and histology was observed in 31% of the patients.…”

“…Overall, CAP values for S0, S1, S2 and S3 were 264 ± 45, 298 ± 48, 331 ± 37 and 336 ± 31 dB/m, respectively [12]. Significantly higher CAP values were seen in patients with S2/S3 steatosis compared to S1 (333 versus 285 dB/m; p < 0.001), and the AUROC of CAP to detect ≥ S2 and S3 was 0.8 and 0.66, respectively [12]. The optimal CAP cut-off for ≥ S2 disease was 310 dB/m [12], which provided a correct assessment of S2/S3 in 86% of the cohort [12].…”

“…However, CAP had limited ability to differentiate between specific grades of steatosis, particularly between grades 2 and 3 [11]. The largest prospective study assessing CAP in NAFLD included 261 patients and explored the relationship between CAP and steatosis grade (S0 to S3) and also looked at discordance rates and factors associated with discordance [12]. Overall, CAP values for S0, S1, S2 and S3 were 264 ± 45, 298 ± 48, 331 ± 37 and 336 ± 31 dB/m, respectively [12].…”

“…The largest prospective study assessing CAP in NAFLD included 261 patients and explored the relationship between CAP and steatosis grade (S0 to S3) and also looked at discordance rates and factors associated with discordance [12]. Overall, CAP values for S0, S1, S2 and S3 were 264 ± 45, 298 ± 48, 331 ± 37 and 336 ± 31 dB/m, respectively [12]. Significantly higher CAP values were seen in patients with S2/S3 steatosis compared to S1 (333 versus 285 dB/m; p < 0.001), and the AUROC of CAP to detect ≥ S2 and S3 was 0.8 and 0.66, respectively [12].…”

Quantitative Imaging Biomarkers of NAFLD

“…A preliminary study in a mixed population of diffuse liver disease reported high correlation of CAP with histological steatosis grade (correlation coefficient 0.81) with excellent severity grading performance and high reproducibility [20]. In a NAFLD population, validation data are still incomplete, but CAP has thus far shown promise as a standardized quantitative US biomarker for steatosis [19, 21]. However, further validation is needed, including evaluation of newer probes optimized for obese patients.…”