Ectopic pregnancy laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Diagnosis can be made by the 7th week of pregnancy (~ 4.5 weeks after conception).

• The definitive diagnosis is made on laparoscopic inspection of the fallopian tube.
• Algorithms have been developed that reduce the need for surgery, and include serial beta-HCG (human chorionic gonadotropin) measurements and transvaginal ultrasound (TVUS).

• Although these algorithms are felt to be 97% sensitive and 95% specific, they may delay the diagnosis.

  • ELISA (enzyme-linked immunosorbent assay) can detect beta-HCG as low as 1.0 IU/L. In the normal pregnancy this doubles every 2 days, whereas abnormal pregnancies (intrauterine or ectopic) have impaired beta-HCG production and longer doubling times.
  • An intrauterine gestation can generally be seen on TVUS when the beta-HCG is > 1500 IU/L (generally ~ 5 – 6 weeks gestation).
  • Absence of an intrauterine gestation with beta-HCG concentrations above this level is diagnostic of an EP (100% sensitive and specific).
  • The presence of an adnexal mass when the beta-HCG is > 1,000 IU/L has a sensitivity of 97%, a specificity of 99%, and a PPV and NPV of 98%.

• Other algorithms use serum progesterone measurements and/or uterine curettage.

  • If the serum progesterone is > 25 ng/ml, EP can be excluded (sensitivity of 97.5%).
  • Curettage is done only after a non-viable pregnancy has been confirmed by either a serum progesterone < 5 ng/ml (100% sensitivity) or by the absence of a rise in beta-HCG after 2 days.
  • If the progesterone is between 5 and 25 ng/ml a TVUS should be performed.

• A decrease in the beta-HCG of ≥ 15% 8 – 12 hours after curettage is diagnostic of complete abortion. If the beta-HCG does not fall, EP is diagnosed.

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