Disclosed herein is a personalized method for monitoring a condition or disorder associated with antibody production in a subject. The method can involve treating a biological sample comprising immunoglobulin from the subject to enzymatically cleave a target immunoglobulin associated with the PCD into one or more variable domain peptide fragments of the target immunoglobulin, and then measuring the one or more variable domain peptide fragments in the sample by quantitative mass spectrometry to quantify the amount of the target immunoglobulin in the sample.