Controlled attenuation parameter (CAP) for the diagnosis of steatosis: a prospective study of 5323 examinations

Controlled attenuation parameter (CAP) evaluated with transient elastography (FibroScan®) is a recent method for non-invasive assessment of steatosis. Its usefulness in clinical practice is unknown. We prospectively investigated the determinants of CAP failure and the relationships between CAP and clinical or biological parameters in a large cohort of consecutive patients.

All CAP examinations performed in adult patients with suspected chronic liver disease were included. CAP failure was defined as zero valid shot. The following factors were analyzed for their influence on CAP value and the relationships between CAP and clinico-biological parameters: age, gender, body mass index, waist circumference, hypertension, diabetes, metabolic syndrome, alcohol use, liver stiffness measurement, indication, and different biological parameters.

CAP failure occurred in 7.7% of 5323 examinations. By multivariate analysis, factors independently associated with CAP measurement failure were female gender, BMI, and metabolic syndrome. By multivariate analysis, factors significantly associated with elevated CAP were BMI [25-30]kg/m(2), BMI >30kg/m(2), metabolic syndrome, alcohol >14 drink/week and liver stiffness >6kPa. CAP increased with the number of parameters of metabolic syndrome, BMI, waist circumference, the presence of diabetes or hypertension, and the cause of the disease. In the 440 patients with liver biopsy, for the diagnosis of steatosis >10%, steatosis >33%, and steatosis >66%, AUROCs of CAP were 0.79 (95% CI 0.74-0.84, p<0.001), 0.84 (95% CI 0.80-0.88, p<0.001), 0.84 (95% CI 0.80-0.88, p<0.001), respectively.

CAP provides an immediate assessment of steatosis simultaneously with liver stiffness measurement. The strong association of CAP with the metabolic syndrome and alcohol use could be of interest for the follow-up of NAFLD or alcoholic patients.