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

Abstract 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 AUROC s 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.