Ultrasound and FibroScan® Controlled Attenuation Parameter in patients with MAFLD: head to head comparison in assessing liver steatosis

Background Controlled attenuation parameter (CAP) has been suggested as a new non-invasive measurement performed during transient elastography (TE) to assess liver steatosis. The aim of this study was to evaluate CAP values head to head with ultrasound (US) as reference standard.Methods A consecutive cohort of patients attending abdominal US in an outpatient liver unit was included in this study with simultaneous CAP determination using the FibroScan (R) M probe and fibrosis scored by TE. Patients were subdivided in four groups on the basis of risk factors for Metabolically Associated Fatty Liver Disease (MAFLD).Results Four hundred thirty-five patients were included in the analysis: 221 (51%) were male; 117 (26.9%) were in control group, 144 (33.1%) in group 2 with inactive HCV or HBV infection and at low-risk for MAFLD, 134 (30.8%) in group 3 at high-risk of MAFLD, 40 (9.2%) in group 4 at high-risk of MAFLD and concomitant inactive HCV or HBV infection. Liver steatosis detected with US evaluation was observed in the 41% of the entire cohort; in particular in the 3.4%, 20.1%, 83.6% and 87.4% of the group 1, 2, 3 and 4, respectively (p < 0.001). In patients at high-risk factor for MAFLD (group 3 and 4), CAP median levels were found statistically different among the severity-grading groups for US steatosis (S0 [n.27], >= S1 [n.59], >= S2 + S3 [n.89]), observing higher CAP levels in patients with a higher steatosis grade (>= S2 + S3 327.5 [+/- 40.6] vs >= S1 277.7 [+/- 45.6] vs S0 245.1 [+/- 47.4]; p < 0.001 for the whole cohort analysis) (p < 0.001 between >= S2 + S3 and >= S1) (p < 0.001 between >= S2 + S3 and S0) (p = 0.004 between >= S1 and S0). ROC analysis showed that the global performance of the CAP median level >= 258 to predict liver steatosis (S0 vs S1-3), was excellent with an Area Under the Curve (AUC) value of 0.87 [CI 95% 0. 835-0.904] with an 84% of sensitivity and a 78% of specificity, and a positive predictive value (PPV) of 73% and negative predictive value (NPV) of 88%. A TE-kPa median value <8.0 was detected in the 100%, 84%, 83.6% and 60% of patients in group 1, 2, 3 and 4, respectively. A TE-kPa median value >13.0 was detected in the 0%, 4.2%, 5.2% and 17.5% of patients in group 1, 2, 3 and 4, respectively.Conclusions CAP values are strongly associated with the standard US criteria for different degree of steatosis. Integrating TE up to 5% of patients may be identified at risk for advanced fibrosis.