Measurement of β-hCG in cul-de-sac fluid vs. serum in the rapid detection of ectopic pregnancy

Objective

This study was designed to assess the value of measuring the cul-de-sac fluid to serum β-hCG ratio as a rapid test for the detection of ectopic pregnancy.

Main outcome measure

The parameter chosen was the level of the β-hCG in cul-de-sac fluid vs. that in serum (D/S ratio).

Design

This prospective controlled hospital-based study included 53 patients. The control group was 25 patients, who were being treated with in vitro fertilization. Group A comprised 15 patients who had had an intra-uterine miscarriage, histologically proven after suction curettage. Group B included 13 patients treated by laparoscopy for a histologically proven ectopic pregnancy. In each group β-hCG was measured in both serum and cul-de-sac fluid and the appropriate D/S ratio was calculated.

Results

In the control group the mean D/S ratio was 0.49 (SEM = 0.03). The mean D/S ratio in group A was 0.78 (SEM = 0.14). In group B the mean D/S ratio was 8.47 (SEM = 2.53). The differences in D/S ratio between the control group and group A were statistically significant (P < 0.05).The differences in D/S ratio between the control group and group B were statistically highly significant (P < 0.00001). Of more interest is the fact that the difference in the D/S ratio between group A and group B was also statistically highly significant (P < 0.0005).

Conclusion

The D/S ratio for β-hCG can be used as a rapid and reliable biochemical test to distinguish between eutopic and ectopic implantation in the pathological pregnancy.