Provided are in vitro serologic methods of assessing the presence of, and assessing the progression of, liver fibrosis in a subject. Also provided are methods of assessing efficacy of an agent for the treatment of liver fibrosis, and methods of treating liver fibrosis. The methods involve quantitatively measuring di-sialylated and mono-sialylated O-glycoforms of a peptide fragment of hemopexin (HPX) in a test serum sample obtained from a test subject, and comparing the measured amounts of di-sialylated and mono-sialylated O-glycoforms of the peptide fragment of hemopexin to a reference amount. In certain embodiments, the measuring is performed using LC-MS/MS-MRM (liquid chromatography/tandem mass spectrometry/multiple reaction monitoring). In certain embodiments, the measuring is performed using LC/MS3 (liquid chromatography with triple-stage mass spectrometric detection).