Controlled Attenuation Parameter (CAP): a noninvasive method for the detection of hepatic steatosis based on transient elastography

Liver Int. 2012 Jul;32(6):902-10. doi: 10.1111/j.1478-3231.2012.02781.x. Epub 2012 Mar 21.


Background: Accurate tools for the noninvasive detection of hepatic steatosis are needed. The Controlled Attenuation Parameter (CAP) specifically targets liver steatosis using a process based on transient elastography.

Methods: Patients with chronic liver disease and body mass index (BMI) ≥28 kg/m(2) underwent biopsy and liver stiffness measurement (LSM) with simultaneous CAP determination using the FibroScan(®) M probe. The performance of the CAP for diagnosing steatosis compared with biopsy was assessed using areas under receiver operating characteristic curves (AUROC).

Results: A total of 153 patients were included: 69% were male, median BMI was 32 kg/m(2); 47% had nonalcoholic fatty liver disease (NAFLD); and 65% had significant (≥10%) steatosis. The CAP was significantly correlated with the percentage of steatosis (ρ = 0.47) and steatosis grade (ρ = 0.51; both P < 0.00005). The median CAP was higher among patients with significant steatosis (317 [IQR 284-339] vs. 250 [227-279] dB/m with <10% steatosis; P < 0.0005) and the AUROC for this outcome was 0.81 (95% CI 0.74-0.88). At a cut-off of 283 dB/m, the CAP was 76% sensitive, 79% specific, and had positive and negative predictive values of 87% and 64%, respectively. CAP performance was not influenced by measurement variability, but was higher in patients with mild (F0-F1) fibrosis (AUROC 0.89 vs. 0.72 with F2-F4; P = 0.03). The AUROCs of the CAP for ≥5%, >33% and >66% steatosis were 0.79, 0.76 and 0.70, respectively.

Conclusions: The CAP is a promising tool for the noninvasive detection of hepatic steatosis. Advantages of CAP include its ease of measurement, operator-independence and simultaneous availability with LSM for fibrosis assessment.

Publication types

  • Comparative Study
  • Multicenter Study
  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Adult
  • Biopsy
  • Body Mass Index
  • Chi-Square Distribution
  • Chronic Disease
  • Elasticity Imaging Techniques*
  • Fatty Liver / diagnosis*
  • Fatty Liver / diagnostic imaging
  • Fatty Liver / pathology
  • Female
  • Humans
  • Liver / diagnostic imaging*
  • Liver / pathology
  • Liver Cirrhosis / diagnosis*
  • Liver Cirrhosis / diagnostic imaging
  • Liver Cirrhosis / pathology
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Non-alcoholic Fatty Liver Disease
  • Ontario
  • Predictive Value of Tests
  • Prospective Studies
  • ROC Curve
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Severity of Illness Index