Research Article: Factors Affecting the Accuracy of Controlled Attenuation Parameter (CAP) in Assessing Hepatic Steatosis in Patients with Chronic Liver Disease

Date Published: June 5, 2014

Publisher: Public Library of Science

Author(s): Kyu Sik Jung, Beom Kyung Kim, Seung Up Kim, Young Eun Chon, Kyung Hyun Cheon, Sung Bae Kim, Sang Hoon Lee, Sung Soo Ahn, Jun Yong Park, Do Young Kim, Sang Hoon Ahn, Young Nyun Park, Kwang-Hyub Han, James Fung.


Controlled attenuation parameter (CAP) can measure hepatic steatosis. However, factors affecting its accuracy have not been described yet. This study investigated predictors of discordance between liver biopsy (LB) and CAP.

A total of 161 consecutive patients with chronic liver disease who underwent LB and CAP were enrolled prospectively. Histological steatosis was graded as S0 (<5%), S1 (5–33%), S2 (34–66%), and S3 (>66% of hepatocytes). Cutoff CAP values were calculated from our cohort (250, 301, and 325 dB/m for ≥S1, ≥S2, and S3). Discordance was defined as a discrepancy of at least two steatosis stages between LB and CAP.

The median age (102 males and 59 females) was 49 years. Repartition of histological steatosis was as follows; S0 26.1% (n = 42), S1 49.7% (n = 80), S2 20.5% (n = 33), and S3 3.7% (n = 6). In multivariate linear regression analysis, CAP value was independently associated with steatosis grade along with body mass index (BMI) and interquartile range/median of CAP value (IQR/MCAP) (all P<0.05). Discordance was identified in 13 (8.1%) patients. In multivariate analysis, histological S3 (odd ratio [OR], 9.573; 95% confidence interval [CI], 1.207–75.931; P = 0.033) and CAP value (OR, 1.020; 95% CI, 1.006–1.034; P = 0.006) were significantly associated with discordance, when adjusting for BMI, IQR/MCAP, and necroinflammation, reflected by histological activity or ALT level. Patients with high grade steatosis or high CAP values have a higher risk of discordance between LB and CAP. Further studies are needed to improve the accuracy of CAP interpretation, especially in patients with higher CAP values.

Partial Text

Currently, the clinical implications of hepatic steatosis are gaining more attention not only in Western countries, but also in Asian countries with a westernized lifestyle such as Japan, China, and Korea. [1], [2] Indeed, the incidence of non-alcoholic fatty liver disease (NAFLD), the most common condition of steatosis, is increasing worldwide and it is now the most common cause of abnormal liver function tests and chronic liver disease (CLD) in both developed and developing countries. [3].

Although CAP showed promising results for non-invasive diagnosis of the significant steatosis, it is not obvious whether quantification of steatosis assessed by CAP could stratify severity of steatosis accurately in patients with severe steatosis. [15]–[18] Myer et al. reported that the diagnostic performance of CAP to identify severe steatosis was sub-optimal [16], and the ability to differentiate between steatosis grade 2 and 3 was not satisfactory in the studies by Sasso et al. and Ledinghen et al.[15], [17] Consistent with these results, a high steatotic burden (steatosis grade 3 or high CAP values) was selected as the independent risk factor of discordant results between LB and CAP in our study.