title: The diagnostic effectiveness of an initial transvaginal scan in detecting ectopic pregnancy.
abstract: BACKGROUND
  To determine the effectiveness of an initial transvaginal ultrasound scan (TVS) in the detection of ectopic pregnancy in consecutive women attending an early pregnancy unit (EPU).
  
  
  METHODS
  This was a prospective observational study. Unselected women attending a dedicated EPU underwent a TVS. Women were classified as having an intrauterine pregnancy (IUP), ectopic pregnancy or pregnancy of unknown location (PUL). Women with a PUL were followed up until the final location of the pregnancy was determined. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) with 95% confidence intervals (CIs) for the initial TVS in the diagnosis of ectopic pregnancy were calculated.
  
  
  RESULTS
  During a one-year study period, 5318 consecutive women attended the EPU. Outcome data were available for 5240 (98.5%) women. Of these, the initial TVS showed an IUP in 4693 (89.6%) cases and an ectopic pregnancy in 91 (1.7%) cases. The remaining 456 (8.7%) women were classified as PUL, and of these 31 (6.8%) were subsequently found to have ectopic pregnancies. The overall sensitivity of the initial TVS in the diagnosis of ectopic pregnancy was 73.9% (95% CI: 65.1-81.6) with a specificity of 99.9% (95% CI: 99.8-100), a PPV of 96.7% (95% CI: 90.7-99.3) and an NPV of 99.4% (95% CI: 99.2-99.6).
  
  
  CONCLUSIONS
  In unselected women attending an EPU, pregnancy location can be diagnosed accurately in over 90% of all pregnancies and in 73.9% of ectopic pregnancies with a single TVS.
authors.affiliation: Early Pregnancy and Gynaecological Ultrasound Unit, Department of Obstetrics and Gynaecology, St George's, University of London, Cranmer Terrace, London, UK. ejkirk@hotmail.co.uk
authors.forename: Emma
authors.initials: E
authors.lastname: Kirk
authors.forename: Aris T
authors.initials: AT
authors.lastname: Papageorghiou
authors.forename: George
authors.initials: G
authors.lastname: Condous
authors.forename: Linda
authors.initials: L
authors.lastname: Tan
authors.forename: Shabana
authors.initials: S
authors.lastname: Bora
authors.forename: Tom
authors.initials: T
authors.lastname: Bourne
mesh_terms: D006063:Chorionic Gonadotropin / Q000097:blood; D005260:Female; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011271:Pregnancy, Ectopic / Q000175:diagnosis*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000295:instrumentation* / Q000379:methods*
chemical_list: D006063:Chorionic Gonadotropin