A pilot study of discovery and validation of peritoneal endometriosis biomarkers in peritoneal fluid and serum
ObjectiveTo identify potential serum biomarkers in women with peritoneal endometriosis (PE) by first looking at its source in the peritoneal fluid (PF).DesignCase-control pilot studies, comprising independent discovery and validation sets.SettingKK Women’s and Children’s Hospital, Singapore.Patient(s)Women with laparoscopically confirmed PE and absence of endometriosis (control).Intervention(s)None.Main Outcome Measure(s)In the discovery set, we used untargeted liquid chromatography-mass spectrometry (LC-MS/MS) metabolomics, multivariable and univariable analyses to generate global metabolomic profiles of PF for endometriosis and to identify potential metabolites that could distinguish PE (n=10) from controls (n=31). Using targeted metabolomics, we validated the identified metabolites in PF and sera of cases (n=16 PE) and controls (n=19). We performed the area under the receiver-operating characteristics curve (AUC) analysis to evaluate the diagnostic performance of PE metabolites.Result(s)In the discovery set, PF phosphatidylcholine (34:3) and phenylalanyl-isoleucine were significantly increased in PE than controls groups, with AUC 0.77 (95% confidence interval 0.61-0.92; p=0.018) and AUC 0.98 (0.95-1.02; p<0.001), respectively. In the validation set, phenylalanyl-isoleucine retained discriminatory performance to distinguish PE from controls in both PF (AUC 0.77; 0.61-0.92; p=0.006) and serum samples (AUC 0.81; 0.64-0.99; p=0.004).Conclusion(s)Our preliminary results propose phenylalanyl-isoleucine as a potential biomarker of PE, which may be used as a minimally-invasive diagnostic biomarker of PE.