C4A and plasma cell myeloma: AUC-values were also determined for the combination of C4 and PON1 using logistic regression analysis to discriminate between the different groups, with a value of 0.695 for pre-malignant myeloma v no bone disease, 0.801 for pre-malignant myeloma v high bone disease and 0.702 for no bone disease v high bone disease.