Interobserver reproducibility of the controlled attenuation parameter (CAP) for quantifying liver steatosis.

Purpose: This study was conducted to prospectively investigate the interobserver reproducibility of controlled attenuation parameter (CAP) measurements and the relationship among the CAP and body mass index (BMI), gender and age.

Methods: Consecutive subjects were studied using the M+ probe of the FibroScan device (Echosens, Paris, France). Measurements were performed by two raters (rater1 and rater2). Interobserver agreement was assessed by using the concordance correlation coefficient (CCC). The Pearson r coefficient was used to test correlation between two study variables, and linear regression was used for the multivariate model.

Results: Three hundred fifty-one subjects (227 males and 124 females) were prospectively studied. The CCC was 0.82 (95 % CI 0.78-0.85) overall, 0.80 (95 % CI 0.75-0.85) for BMI <25 kg/m(2), 0.76 (95 % CI 0.69-0.84) for BMI 25-29 kg/m(2) and 0.65 (95 % CI 0.41-0.88) for BMI ≥30 kg/m(2). The CCC was 0.44 (95 % CI 0.31-0.56) for CAP values ≤240 dB/m and 0.72 (95 % CI 0.65-0.79) for CAP values >240 dB/m. In univariate analysis, age and BMI by gender were correlated with the CAP. Multiple regression analysis confirmed the relationship of the CAP with age and BMI, but not with gender.

Conclusions: The results of this study show that the interreader agreement in CAP measurement is good. In healthy volunteers, the CAP is strongly correlated with age and BMI.