BACKGROUND: This study aimed to determine the diagnostic role of serum levels of complement C1q, Bb, and H in nonpregnant women, women with normal pregnancy, and women with severe pre-eclampsia.

MATERIAL AND METHODS: Healthy nonpregnant women (n=30), women with early, middle, and late normal pregnancy (n=30, respectively), and women with severe pre-eclampsia (n=73) were studied. The pre-eclampsia study group included early-onset cases (n=43) and late-onset cases (n=30). Serum levels of Bb were determined by enzyme-linked immunosorbent assay (ELISA), and C1q and H were tested by a turbidimetric immunoassay method.

RESULTS: In the pre-eclampsia study group, compared with women with normal pregnancy, serum levels of C1q remained stable throughout pregnancy, and Bb levels declined from mid-pregnancy (p=0.250). Serum levels of factor H increased in the middle and late stages of pregnancy, and C1q and H were lower in early-onset severe pre-eclampsia (p<0.001, p=0.009, respectively) and late-onset severe pre-eclampsia (p<0.001, p=0.031, respectively) compared with the early-onset control and late-onset control groups. Serum levels of Bb increased in early-onset severe pre-eclampsia (p=0.001) and late-onset severe pre-eclampsia (p=0.003) compared with early-onset control and late-onset control groups. The area under the receiver operator curve (ROC) for serum C1q, Bb, and H for the diagnosis of early-onset severe pre-eclampsia were 0.814 (95% CI, 0.712–0.917), 0.743 (95% CI, 0.638–0.859), and 0.681(95% CI, 0.556–0.806), and late-onset severe pre-eclampsia were 0.805 (95% CI, 0.694–0.913), 0.796 (95% CI, 0.680–0.911), and 0.662 (95% CI, 0.524–0.800).

CONCLUSIONS: The classical and alternative pathways of complement were activated in patients with severe pre-eclampsia. Serum levels of C1q, Bb, and H should be studied further as potential diagnostic markers for severe pre-eclampsia.

Keywords: Complement C1q, Complement Factor B, Complement Factor H, Pre-Eclampsia, Area Under Curve, Case-Control Studies, Pregnancy, ROC Curve