title: Beta-human chorionic gonadotropin levels and the likelihood of ectopic pregnancy in emergency department patients with abdominal pain or vaginal bleeding.
abstract: Strategies for diagnosing ectopic pregnancy that defer endovaginal ultrasound in women with suggestive symptoms and serum beta-human chorionic gonadotropin (beta-hCG) levels less than 1500 mIU/mL ignore the increased risk of ectopic pregnancy in these patients.
  
  
  OBJECTIVE
  To quantify this increased risk by establishing and comparing the beta-hCG distributions of symptomatic women with ectopic pregnancies, abnormal intrauterine pregnancies, and normal intrauterine pregnancies.
  
  
  METHODS
  The authors reviewed the records of a cohort of women who visited an urban emergency department (ED) during a 34-month period with abdominal pain or vaginal bleeding and non-zero quantitative beta-hCG levels. Explicit criteria were used to determine whether the pregnancy ultimately turned out to be intrauterine and normal, intrauterine and abnormal, or ectopic. Probability distributions were compared using frequency distributions, receiver operating characteristic (ROC) curves, and likelihood ratios.
  
  
  RESULTS
  Of 730 ED patients included in the analysis, 96 (13%) had ectopic pregnancies, 253 (35%) had abnormal intrauterine pregnancies, and 381 (52%) had normal intrauterine pregnancies. The beta-hCG distributions of patients with ectopic pregnancies and abnormal intrauterine pregnancies were similar and much lower than the beta-hCG distribution of patients with normal intrauterine pregnancies. A beta-hCG level less than 1500 mIU/mL more than doubled the odds of ectopic pregnancy (likelihood ratio = 2.24). Of the 158 patients with beta-hCG below 1500 mIU/mL, 40 (25%; 95% confidence interval [CI] = 19% to 32%) had ectopic pregnancies, and only 25 (16%; CI = 11% to 22%) had normal intrauterine pregnancies.
  
  
  CONCLUSIONS
  In women with pain or bleeding and serum beta-hCG levels less than 1500 mIU/mL, the risk of ectopic pregnancy is substantially increased, while the likelihood of normal intrauterine pregnancy is low.
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, USA. mkohn@itsa.ucsf.edu
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kohn
authors.forename: Kristi
authors.initials: K
authors.lastname: Kerr
authors.forename: David
authors.initials: D
authors.lastname: Malkevich
authors.forename: Nelda
authors.initials: N
authors.lastname: O'Neil
authors.forename: M James
authors.initials: MJ
authors.lastname: Kerr
authors.forename: Beth C
authors.initials: BC
authors.lastname: Kaplan
mesh_terms: D015746:Abdominal Pain / Q000097:blood*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000097:blood / Q000175:diagnosis*; D014592:Uterine Hemorrhage / Q000097:blood / Q000175:diagnosis*
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human