CXCL8 and endometriosis: While no association between the presence of acyclic pelvic pain and IL-8 levels was observed among the endometriosis cases (Figure 4; Table S3), we did note a borderline significant interaction with analgesic use for the association between the presence of acyclic pelvic pain and IL-8 among the cases (p-interaction = 0.06; Table S10).