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CAP ultrasound provides noninvasive measurement of hepatic steatosis

Controlled attenuation parameter, or CAP, provided a standardized, noninvasive measure of hepatic steatosis, particularly when comorbid liver disease, BMI and diabetes were considered, according to a recently published meta-analysis.

“CAP measurement is an easy and fast examination providing a numerical value, which correlates with the histological degree of steatosis. It has been studied in more than 20 biopsy controlled studies which evaluated its correlation with histologically defined steatosis,” Thomas Karlas, MD, from the University Hospital of Leipzig, and colleagues wrote. “However, the routine use of CAP is limited due to uncertainty as to the optimal cut-off values between different steatosis grades and regarding the influence of different covariates. We conducted an individual patient data meta-analysis ... on CAP accuracy for non-invasive grading of liver steatosis.”

The researchers reviewed 19 studies containing histology verified CAP data and biopsy results of 2,735 eligible patient cases. Mean patient age was 45.5 years, 37.7% were female and mean BMI was 25 kg/m². CAP was performed within one day of biopsy in 1,634 patients and in one week of biopsy in 2,685 patients.

The researchers determined the optimal cut-offs to be 248 dB/m (95% CI, 237-261) for steatosis grade greater than S0, 268 dB/m (95% CI, 257-284) for steatosis grade greater than S1, and 280 dB/m (95% CI, 268-294) for steatosis grade greater than S2. BMI, diabetes and etiology of liver disease had a significant and relevant influence on CAP.

Patients with NAFLD or NASH classified at steatosis grade S1 had approximately 5.2% (95% CI, 2.5-7.9) more affected hepatocytes than other etiologies. In patients with NAFLD or NASH at grade S2, the difference was only 3.6% (95% CI, 0.3-7), while there was no differential indication for grade S3.

Patients with NAFLD or NASH had increased CAP values of 16 dB/m (95% CI, 6-26) and patients with diabetes had an increased value of 13 dB/m (95% CI, 3-25). CAP values also increased by 3.9 dB/m (95% CI, 2.9-5) per BMI unit.

“Transient elastography has been an object of research for over 10 years now. Initially, it was seen primarily as a surrogate for fibrosis estimation, but liver stiffness gradually emerged as a distinct diagnostically relevant parameter reflecting disease severity and prognosis,” the researchers wrote. “Thinking of CAP, it is somewhat early to speculate about future applications, but an analogous progression is conceivable, especially considering the impact of steatosis on fibrosis progression in NAFLD patients.” – by Talitha Bennett

Disclosures: The researchers report no relevant financial disclosures.