Haptoglobin β chain isoforms in the plasma and peritoneal fluid of women with endometriosis

Objective: To estimate the expression of haptoglobin (Hp) β chain isoforms in the peritoneal fluid (PF) and plasma (PL) of women with and without endometriosis. Design: Cross-sectional study. Setting: University hospital. Patient(s): Seventy-two patients with endometriosis and 35 controls. Intervention(s): Peritoneal fluid and PL samples were subjected to two-dimensional gel electrophoresis, silver stained, digitally captured, and compared by semiquantitative computerized analysis. Main Outcome Measure(s): Expression of Hp β chain isoforms. Result(s): No significant difference was observed in the frequency of expression of the Hp β chain isoforms between the two groups. One β chain isoform (HpβE; molecular weight, 38.40 ± 0.94 kD; and isoelectric point, 5.63 ± 0.17) had significantly higher expression in both the PF and PL of women with endometriosis than in the PF and PL of controls. No significant difference was observed in HpβE expression between women with mild (revised American Fertility Society [rAFS], stage I-II) and severe (rAFS, stage III-IV) endometriosis. In the control group, HpβE expression was correlated with the phase of the menstrual cycle. Conclusion(s): Women with endometriosis have higher PF and PL levels of HpβE. Further investigation should be aimed at producing antibodies against the HpβE-specific epitopes to determine whether its measurement may improve the clinical diagnosis of endometriosis.