*3.6. Discrimination of Significant Liver Fibrosis by the miRFIB-Score*

To investigate whether a combination of the evaluated miRNAs could be used to diagnose significant (F ≥ 2) liver fibrosis with a higher predictive value than the individual miRNAs, we created an miRNA-algorithm using logistic regression analysis. Here, the total patient cohort (*n* = 208) was randomly divided (Excel, Microsoft, WA, USA) into a derivation (*n* = 143) and validation (*n* = 65) cohort. Considering the lack of association between miRNA-378a-3p and fibrosis severity (Figure 3 and Supplementary Table S4), we chose to exclude this miRNA from the score. Combination of the other miRNA-variables generated the miRFIB-score:

miRFIB = 4.3799 + (0.70824 × Let-7f-5p (dCT)) − (0.090912 × miRNA-122-5p (dCT)) − (0.26149 × miRNA-142-5p (dCT)) − (0.53602 × miRNA-29a-3p (dCT)) − (0.041140 × miRNA-451a (dCT)).


**Table 2.** Correlations of circulating miRNA expression levels with clinical parameters.

Correlations were evaluated by the Pearson's correlation coefficient (r). ns: not significant; BMI: body mass index; AST: aspartate aminotransferase; ALT: alanine aminotransferase; Alk Phos: alkaline phosphatase; GGT: gamma-glutamyl transferase; AST/ALT ratio: aspartate aminotransferase/alanine aminotransferase ratio; APRI: AST to platelet ratio index; Fib-4: Fibrosis-4; PRTA-score: PDGFRβ-thrombocytes-albumin score.

The diagnostic value of the miRFIB-score to diagnose significant liver fibrosis in the derivation cohort was superior (AUC = 0.7251) to the clinical scores AST/ALT, APRI, and Fib-4 (AUC of 0.5936, 0.6273, and 0.6773, respectively). The diagnostic value of the miRFIB-score was confirmed in the validation cohort (AUC = 0.8173) and total cohort (AUC = 0.7558) (Table 3 and Figure 5). Additionally, the miRFIB-score was found to be significantly correlated with fibrosis severity (r = 0.4365) (Supplementary Table S4) and was able to differentiate patients with specific stage F2 from patients with stage F0–1 (*p* < 0.0001) (Supplementary Figure S2).
