Steatosis Assessment with Controlled Attenuation Parameter (CAP) in Various Diseases

(ENG) Controlled attenuation parameter (CAP) has gained ground as a noninvasive, point-of-care modality for liver steatosis assessment in patients with suspected chronic liver disease of various etiologies, but particularly non-alcoholic fatty liver disease. CAP has good to excellent accuracy for detecting any steatosis (defined as ≥S1, a liver biopsy showing >5% hepatocytes with lipid droplets). However, CAP’s diagnostic accuracy is less good for moderate and severe steatosis, with AUROCs in most studies below 0.80–0.85. An individual-patient data meta-analysis found that the optimal cutoff for diagnosing any steatosis was 248 dB/m (AUROC 0.82, sensitivity 69%), moderate steatosis 268 dB/m (AUROC 0.87, sensitivity 77%), and severe steatosis 280 dB/m (AUROC 0.88, sensitivity 88%). In spite of several diagnostic studies, CAP generalizability is currently limited by large between-study variation. This results in highly varied optimal cutoffs across the existing literature, substantial differences in sensitivity and specificity, and heterogeneity in selection of patients. In spite of this, CAP maintains its new role as an optimal test for screening, diagnosing, and monitoring steatosis in chronic liver disease patients: It is point of care, continuous rather than ordinal, noninvasive, radiation free, and does not require the same costs and resources as magnetic resonance imaging.