Concentration of serum biomarkers such as CA125, transthyretin, and apolipoprotein A1 in serum from healthy individuals, benign patients, and ovarian cancer patients was simultaneously measured by a multiplex liquid array system using microbeads coated with capture antibodies and biotin-labeled antibodies against each of the tumor markers and streptavidin-R-phycoerythrin. Here, TTR is linked to ovarian cancer.