The same group developed a multiplex selected reaction monitoring (SRM) assay to detect the level of testis-expressed protein 101 (TEX101) and epididymis-expressed extracellular matrix protein 1 (ECM1) to distinguish men with obstructive azoospermia from those with non-obstructive azoospermia (Table 2). Here, ECM1 is linked to Azoospermia.