CAP (Controlled Attenuation Parameter): Interpretation of Steatosis S0–S3 and Joint Assessment with Fibrosis
Method Principle
Controlled Attenuation Parameter (CAP) is a method for the quantitative assessment of liver steatosis, associated with transient elastography (TE) and performed on the FibroScan device. The method is based on measuring ultrasound attenuation, directed by VCTE measurement, and is expressed in dB/m.
Correlation with Histology
In a cohort of 115 patients using the histological degree of steatosis as a reference, CAP significantly correlated with steatosis (r=0.81, p<0.00001). The AUROC for detecting >10% and >33% steatosis were 0.91 and 0.95, respectively. A meta-analysis (11 studies) showed AUROC for predicting S≥1, S≥2, and S≥3 as 0.85, 0.88, and 0.87, respectively.
CAP Threshold Values (EFSUMB)
| Steatosis Grade | CAP Threshold, dB/m |
|---|---|
| S≥1 | 232.5 |
| S≥2 | 255 |
| S≥3 | 290 |
The specified threshold values are proposed for diagnosing S≥1, S≥2, and S≥3, respectively.
Joint Assessment with Fibrosis
CAP is associated with TE and performed on the FibroScan device, allowing simultaneous data acquisition on steatosis and fibrosis assessment using transient elastography. Detailed criteria for matching steatosis and fibrosis grades are not provided in the given fragments. [clarify]
Frequently asked questions
What CAP thresholds differentiate steatosis grades?
Proposed thresholds: S≥1 — 232.5 dB/m, S≥2 — 255 dB/m, S≥3 — 290 dB/m (EFSUMB Course Book, 2018).
How well does CAP correlate with the histological degree of steatosis?
In a cohort of 115 patients, the correlation was r=0.81 (p<0.00001) using the histological degree of steatosis as a reference.
What is the diagnostic accuracy of CAP according to meta-analysis data?
The AUROC for S≥1, S≥2, and S≥3 were 0.85, 0.88, and 0.87, respectively (meta-analysis of 11 studies).
On what equipment is CAP performed?
CAP is performed on the FibroScan device and is associated with transient elastography (TE).