Problem The lack of a reliable method for early non-invasive detection of endometriosis often results in delayed diagnosis. The aim of this study was to test the hypothesis that the plasma concentration of complement factor C3a (anaphylatoxin) can be used as a non-invasive test in the diagnosis of endometriosis.
Method of study The C3a concentration was analyzed using ELISA in 160 patients with (n = 109) or without (n = 51) endometriosis during menstruation (n = 49), follicular phase (n = 55), and luteal (n = 56) phase.
Results Plasma C3a concentration was comparable between patients with [102 (27–2213) ng/mL] and without [105 (32–2340) ng/mL] (P = 0.84) endometriosis, also when assessed separately during menstruation, follicular phase, and luteal phase.
Conclusion We found no difference in C3a levels between women with and without endometriosis and did not confirm our hypothesis that plasma C3a levels can be used as diagnostic test for endometriosis.