The Fibrinogen-to-Albumin Ratio in Endometriosis: A Step Toward Personalized Non-Invasive Diagnostics

<b>Background/Objectives:</b> Endometriosis is a chronic inflammatory disease affecting up to 10-15% of women of reproductive age and is frequently associated with pelvic pain and infertility. Non-invasive biomarkers remain insufficient for accurate diagnosis, often necessitating laparoscopic confirmation. The fibrinogen-to-albumin ratio (FAR), a composite marker of systemic inflammation, has been proposed in both oncological and cardiovascular disease but has not yet been evaluated in endometriosis. <b>Methods:</b> We conducted a retrospective monocentric study including 390 women who underwent laparoscopy between January 2015 and December 2021 at the Medical University of Vienna. Of these, 218 had histologically confirmed endometriosis and 172 had benign ovarian cysts. Preoperative laboratory data was collected, and FAR was calculated. Group comparisons were performed using the Mann-Whitney U test. ANOVA was used to compare FAR across revised American Society for Reproductive Medicine (rASRM) stages, and Spearman's rank correlation assessed associations with disease severity. Subgroup analyses were performed for adenomyosis and deep infiltrating endometriosis (DIE). <b>Results:</b> FAR was significantly higher in women with endometriosis than in controls (median 0.0679, IQR 0.0588-0.0778 vs. 0.0641, IQR 0.0559-0.716; <i>p</i> = 0.0035). Across rASRM stages I-IV, FAR values were comparable (means 0.0691-0.0709) and did not differ significantly (<i>p</i> = 0.822, ANOVA). Spearman's correlation confirmed no significant association with disease stage (ρ = 0.085, <i>p</i> = 0.24). In exploratory analyses, women with adenomyosis (<i>n</i> = 35) showed a non-significant trend toward a higher median FAR compared to those without adenomyosis (0.0707 vs. 0.0669; <i>p</i> = 0.073, one-sided). No difference in FAR was observed between women with deep infiltrating endometriosis (DIE; <i>n</i> = 144) and those without (0.0680 vs. 0.0672; <i>p</i> = 0.389, one-sided). <b>Conclusions:</b> Although FAR alone cannot replace surgical confirmation, the difference observed between the groups may reflect the systemic inflammatory aspect of endometriosis and should be investigated further in future studies. Given its accessibility and cost-effectiveness, FAR may support the development of non-invasive, personalized diagnostic approaches when combined with other clinical and molecular markers.