Abstract: Objective To evaluate serum M30 and M65 levels in patients with acute-on-chronic pre-liver failure （pre-ACLF） and to investigate their value for early diagnosis of acute-on-chronic liver failure （ACLF）. Methods Serum M30 and M65 levels in patients with pre-ACLF（n=35），ACLF（n=40），chronic hepatitis B （CHB，n=20） and healthy controls （n=20） were determined by enzyme-linked immunoabsorbent assay. The clinical significance for early diagnosis of ACLF was analyzed. Results Significantly higher serum M30 and M65 levels were found in patients with ACLF and with pre-ACLF compared with CHB or healthy controls（P<0.05）；In pre-ACLF patients，serum M30 and M65 levels[（493.80±143.85）U/L and（712.47±305.67） U/L] were higher in 15 patients who progressed to ACLF than 20 recovered [（351.40±127.78）U/L and（448.15±165.14） U/L，respectively， P<0.05]；No significant difference was found in serum M30 and M65 levels between 15 patients with pre-ACLF who switched to ACLF and 40 patients with ACLF（P>0.05）；The area under receiver operating characteristic curve （AUC） demonstrated that both serum M30 and M65 had diagnostic value （AUC≥0.80） in identifying early ACLF from pre-ACLF patients（0.877 and 0.867，respectively）；When serum M30 levels were ≥453.70 U/L，the sensitivity and specificity for diagnosis of ACLF was 0.867and 0.850，respectively，and when serum M65 levels were≥626.71 U/L，the sensitivity and specificity for diagnosis of ACLF was 0.800 and 0.850，respectively；No significant difference was found in serum M30 and M65 levels between 20 survived patients with ACLF as compared with 20 died （P>0.05）. Conclusions In patients with pre-ACLF，serum M30 and M65 levels may serve as important biomarkers for early diagnosis of ACLF.

Key words: Acute-on-chronic liver failure, Acute-on-chronic pre-liver failure, Early diagnosis, M30, M65