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Multicenter Study Comparative Study
Controlled Attenuation Parameter (CAP): a noninvasive method for the detection of hepatic steatosis based on transient elastography.
- Robert P Myers, Aaron Pollett, Richard Kirsch, Gilles Pomier-Layrargues, Melanie Beaton, Mark Levstik, Andres Duarte-Rojo, David Wong, Pam Crotty, and Magdy Elkashab.
- Liver Unit, Division of Gastroenterology and Hepatology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada. rpmyers@ucalgary.ca
- Liver Int. 2012 Jul 1; 32 (6): 902-10.
BackgroundAccurate 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.MethodsPatients 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).ResultsA 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.ConclusionsThe 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.© 2012 John Wiley & Sons A/S.
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