Association of Vitamin D-Binding Protein (VDBP) and Endometriosis in Women with Dysmenorrhea: A Case-Control Study

Abstract

Background: Vitamin D-binding protein (VDBP) participates in vitamin D transport, actin clearance, and immune regulation, but its association with endometriosis and disease stage remains uncertain. Objective: This case-control study compared serum VDBP in women with dysmenorrhea with and without endometriosis and assessed paired serum-peritoneal concentrations, disease stage, and diagnostic value.
Methods: It included 24 women with histopathologically confirmed endometriosis and 24 controls without clinical or ultrasonographic evidence of endometriosis. VDBP was measured by enzyme-linked immunosorbent assay. Analyses used an independent-samples t-test without assuming equal variances, a paired-samples t-test, Spearman correlation, and receiver operating characteristic (ROC) analysis.
Results: Mean serum VDBP was higher in cases than controls (428.29 ± 138.60 versus 356.89 ± 71.07 µg/mL; mean difference 71.40 µg/mL; 95% confidence interval [CI] 6.81-135.99; p = 0.031). Peritoneal VDBP in cases was 185.14 ± 67.44 µg/mL and lower than paired serum VDBP (p < 0.001). Serum VDBP correlated positively with stage II-IV disease (ρ = 0.565; p = 0.004). ROC analysis showed limited discrimination (area under the curve 0.615; 95% CI 0.449-0.781; p = 0.176); sensitivity and specificity were both 58.3%.
Conclusion: Serum VDBP concentrations were associated with endometriosis and disease stage, with higher mean concentrations in serum than in peritoneal fluid among cases. Serum VDBP showed limited diagnostic discrimination, and the findings do not support its use as a standalone diagnostic biomarker.