P2RX3 and endometriosis: Additionally, the differences in P2X3 expression score between women with and without pain reached statistical significance for ovarian endometriosis (P = 0.000), peritoneal endometriosis (P = 0.000) and deeply infiltrating endometriosis (P = 0.000), respectively, but no significant differences of P2X3 expression frequency in ovarian endometriosis, peritoneal endometriosis or deeply infiltrating endometriosis between women with and without pain were found (Table 3).