Abstract: Objective To investigate the application value of the Metabolic reaction pathological index (MRPI), a novel non-invasive diagnostic model constructed based on serum type Ⅳ collagen (Ⅳ-C) and pathophysiological dynamics, in evaluating significant liver fibrosis (≥F2) in patients with metabolic dysfunction-associated steatotic liver disease (MASLD). Methods A retrospective analysis was conducted on the clinical data of 202 MASLD patients who underwent liver biopsy at the Fifth People′s Hospital of Wuxi from January 2017 to December 2025. The MRPI model was established based on the non-linear relationship among hepatic microstructural remodeling, mitochondrial injury, and metabolic load. Using the FIB-4 index as a control, the diagnostic efficacy of MRPI for significant liver fibrosis was analyzed using receiver operating characteristic (ROC) curves. Results The median serum type Ⅳ collagen in the significant fibrosis group was significantly higher than that in the non-significant group[80.00 ng/mL vs. 37.00 ng/mL, P<0.001]. The area under the curve (AUC) of the MRPI model for diagnosing significant liver fibrosis was 0.857 (95% CI: 0.808~0.904), which was significantly superior to that of the FIB-4 index[0.749 (95% CI: 0.688~0.817), P<0.001]. At the optimal cut-off value of 2.442, the specificity and sensitivity of MRPI were 93.1% and 61.4%, respectively, with its specificity being significantly higher than that of FIB-4 (65.3%). Conclusion The MRPI model, constructed by combining serum type Ⅳ collagen with metabolic and inflammatory indicators, effectively reflects the pathophysiological process of fibrosis progression in MASLD and demonstrates high specificity and diagnostic efficacy.

Key words: Metabolic dysfunction-associated steatotic liver disease, Liver fibrosis, Type IV collagen, Non-invasive diagnostic model, Pathophysiology