Evaluation of reliability of CAP-measurement in patients with autoimmune liver diseases

Background With increasing prevalence of obesity, concordant NAFLD and NASH are emerging challenges in care of patients with autoimmune liver diseases (AILD). As a risk factor for cirrhosis and HCC development, reliable diagnostic tools to monitor hepatic steatosis are urgently required but only poorly evaluated in this patient cohort.

Aims We aim to evaluate the diagnostic accuracy of controlled-attenuation parameter (CAP) to control its reliability in everyday clinical practice in AILD patients.

Methods Non-invasive ultrasound-based steatosis measurement by CAP was obtained via transient elastography (FibroScan®​, Echosense) in patients with AILD that underwent liver biopsy between 2015-2020 in the University medical center Hamburg-Eppendorf. Performance of CAP in patients with autoimmune hepatitis (AIH), primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) and patients with variant syndromes of AIH and PBC or PSC was evaluated retrospectively by using area under the receiver operating characteristic (AUROC) curve. Correlation between CAP value and clinical/ biochemical parameters within patients with AILD was performed using spearman´s correlation analysis.

Results 433 patients with AILD (AIH: 219, PBC: 48, PSC: 82, AIH/PBC: 62, AIH/PSC: 22) were included in the analysis. Histologically proven steatosis was present in 89 patients (AIH: 21,5%; PBC: 29,2%, PSC:14,81%, AIH/PBC: 24,19%, AIH/PSC: 5,54%). CAP correlated significantly with grade of steatosis and BMI. AUROC-analysis was 0,761 for any grade of steatosis in all AILD. CAP showed to be least reliable in AIH (AUROC: 0,72) compared to PBC (0,80) and PSC (0,90). The optimal cut-off value calculated by Youden`s index was 256 dB/m (sensitivity/specificity: 60%/79,5%), 277 dB/m (71,4%/82,4%) and 245 dB/m (91,7%/ 81,4%) for AIH, PBC or PSC respectively. AIH patients showed higher hepatic inflammation compared to PBC and PSC at time of CAP measurement. In subgroup analysis of AIH patients levels of transaminases correlated negatively with CAP value. However, in multivariate regression analysis CAP maintained a significant correlation with grade of hepatic steatosis and BMI.

Summary CAP measurement is an adequate tool for evaluation of hepatic steatosis in patients with AILD. However, hepatic inflammation seems to have an influence on accuracy of CAP measurement and should be considered as a potential confounder in non-invasive steatosis assessment via CAP.

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Artikel online veröffentlicht:
19. August 2022