Classification performance of combinatorial markers identified through 35-plex panel assay. (a) Principal component analysis (PCA) with 35 markers showed clustering and separation of breast cancer patients (closed circle) and normal subjects (open circle) in the PCA chart using principal component (Comp) 1 and 2. NF = normal female; BC = breast cancer. (b) The area under the curve was calculated for combinatorial markers and a single marker, and compared using a receiver operating curve. CEA = carcinoembryonic antigen; EGF = epidermal growth factor; LDA = linear discriminant analysis; RF = random forests; SVM = support vector machine.