Use of serum progesterone to triage expectant management of tubal ectopic pregnancy.  

Mark Pandrich¹, Nishel Shah^{1, 2} , Dede Ofili-Yebovi¹
Chelsea and Westminster Hospital¹, Imperial College London² 

Corresponding author: mark.pandrich@nhs.net  

Objective: To investigate the utility of serum progesterone (P4) as a triaging tool for women with tubal ectopic pregnancy to identify those likely to have successful expectant management. 

Background: Expectant management is offered for tubal ectopic pregnancy (image 1) in clinically stable women with <35mm pregnancies and where serum HCG is <1000 IU/L. NICE 2019 The role of progesterone in predicting outcome of ectopic pregnancy or suitability for expectant management has not been determined. 

Method: Design: Retrospective cohort study.  94 patients included for analysis. Median age 32, 96% spontaneous pregnancies, 9.6% with history of previous ectopic. 

Inclusion criteria: All women with tubal ectopic pregnancy managed in the early pregnancy unit at a London teaching hospital over a 3-year period (October 2017 to December 2020).  

Results: 26% (n=24) successfully completed expectant management (68% surgical; 6% medical management). Progesterone (P4) concentrations in the expectant management (median 6, IQR 2-9) group were significantly lower than those who had surgical or medical management (median 17, IQR 5.75-29.25; P=0.0005). (Fig.1) Area under the ROC curve (AUC) values for P4, first HCG and peak HCG were 0.733, 0.796 and 0.798 respectively in predicting successful expectant management. (Fig.2 (A), (B), (C), (D)) Combining P4 with first HCG produced greatest AUC value (0.8036) compared to any of other markers alone/combination. (Fig.2(4)- red box). Thresholds to predict successful completion of expectant management: P4 of <12.5 had a sensitivity and specificity of 83.3% (95% CI=64.2-93.3%) and 62.8% (95% CI=51.2-73.2%).First HCG <1028 had a sensitivity and specificity of 79.2% (95% CI=59.5-90.8%) and 55.7 (95% CI=44.1-66.8%). Peak HCG <1520 had a sensitivity and specificity of 95.8% (95% CI=79.8-99.8%) and 44.3 (95% CI=33.3-55.9%). P4 x first HCG <12915 had a sensitivity and specificity of 87.5% (95% CI=69-95.7%) and 60% (95% CI=48.3-70.7%). 

Conclusion: Low serum progesterone performs well as a discriminator for successful expectant management of tubal ectopic pregnancy, especially combined with HCG. 

Take home message: Progesterone has the potential to be used as a tubal ectopic triage tool, combined with first HCG, on suitability for expectant management.