We used ELISA as an orthogonal technology to measure the absolute expression levels of three protein markers (i.e., IGFBP1, CD5L, ANXA1) in which the SomaScan analysis results showed nominally significant association with absolute fold change of >1.2 between endometriosis cases and controls and ELISA assays were commercially available. This evidence concerns the gene IGFBP1 and endometriosis.