FAS and metabolic dysfunction-associated steatohepatitis: Moreover, in patients with biopsy-proven NASH, a higher serum level of soluble Fas (sFas) and sFasL has been discovered compared with patients with simple steatosis [104], and this is the reason why measuring soluble Fas together with CK18 fragments increases the sensitivity (88%) and specificity (89%) in diagnostic processes [85,105].