A proteomic and peptidomics analysis of serum from patients suffering from metabolic dysfunction-associated steatotic liver disease. Proteomics was performed initially on a set of patients with varying degrees of liver disease. Following close analysis of the results, a peptidomics based analysis was performed and identified significant numbers of degraded and oxidised peptides from apolipoproteins. A more targeted peptidomics analysis was performed on a larger cohort and the oxidation status of small apolipoproteins demonstrated a high accuracy of precision for liver disease diagnosis.