title: Diagnostic accuracy of varying discriminatory zones for the prediction of ectopic pregnancy in women with a pregnancy of unknown location.
abstract: OBJECTIVE
  Various serum human chorionic gonadotropin (hCG) discriminatory zones are currently used for evaluating the likelihood of an ectopic pregnancy in women classified as having a pregnancy of unknown location (PUL) following a transvaginal ultrasound examination. We evaluated the diagnostic accuracy of discriminatory zones for serum hCG levels of > 1000 IU/L, 1500 IU/L and 2000 IU/L for the detection of ectopic pregnancy in such women.
  
  
  METHODS
  This was a prospective observational study of women who were assessed in a specialized transvaginal scanning unit. All women with a PUL had serum hCG measured at presentation. Expectant management of PULs was adopted. These women were followed up with transvaginal ultrasound, monitoring of serum hormone levels and laparoscopy until a final diagnosis was established: a failing PUL, an intrauterine pregnancy (IUP), an ectopic pregnancy or a persisting PUL. The persisting PULs probably represented ectopic pregnancies which had been missed on ultrasound and these were incorporated into the ectopic pregnancy group. Three different discriminatory zones (1000 IU/L, 1500 IU/L and 2000 IU/L) were evaluated for predicting ectopic pregnancy in this PUL population.
  
  
  RESULTS
  A total of 5544 consecutive women presented to the early pregnancy unit between 25 June 2001 and 14 April 2003. Of these, 569 (10.3%) women were classified as having a PUL, 42 of which were lost to follow up. Of the 527 (9.5%) cases with PUL analyzed, there were 300 (56.9%) failing PULs, 181 (34.3%) IUPs and 46 (8.7%) ectopic pregnancies. Overall, 74.6% were symptomatic and 25.4% were asymptomatic (P = 8.825E-07). The sensitivity and specificity of an hCG level of > 1000 IU/L to detect ectopic pregnancy were 21.7% (10/46) and 87.3% (420/481), respectively; for an hCG level of > 1500 IU/L these values were 15.2% (7/46) and 93.4% (449/481), respectively, and for an hCG level of > 2000 IU/L they were 10.9% (5/46) and 95.2% (458/481), respectively.
  
  
  CONCLUSIONS
  Varying the discriminatory zone does not significantly improve the detection of ectopic pregnancy in a PUL population. A single measurement of serum hCG is not only potentially falsely reassuring but also unhelpful in excluding the presence of an ectopic pregnancy.
authors.affiliation: Early Pregnancy, Gynaecological Ultrasound and Minimal Access Surgery Unit, Department of Obstetrics & Gynaecology, St George's Hospital Medical School, London, UK. gcondous@hotmail.com
authors.forename: G
authors.initials: G
authors.lastname: Condous
authors.forename: E
authors.initials: E
authors.lastname: Kirk
authors.forename: C
authors.initials: C
authors.lastname: Lu
authors.forename: S
authors.initials: S
authors.lastname: Van Huffel
authors.forename: O
authors.initials: O
authors.lastname: Gevaert
authors.forename: B
authors.initials: B
authors.lastname: De Moor
authors.forename: F
authors.initials: F
authors.lastname: De Smet
authors.forename: D
authors.initials: D
authors.lastname: Timmerman
authors.forename: T
authors.initials: T
authors.lastname: Bourne
mesh_terms: D015415:Biomarkers / Q000097:blood; D006063:Chorionic Gonadotropin / Q000097:blood*; D005260:Female; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000175:diagnosis* / Q000000981:diagnostic imaging; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal
chemical_list: D015415:Biomarkers; D006063:Chorionic Gonadotropin