title: Accuracy of ultrasound for the prediction of placenta accreta.
abstract: OBJECTIVE
  Ultrasound has been reported to be greater than 90% sensitive for the diagnosis of accreta. Prior studies may be subject to bias because of single expert observers, suspicion for accreta, and knowledge of risk factors. We aimed to assess the accuracy of ultrasound for the prediction of accreta.
  
  
  METHODS
  Patients with accreta at a single academic center were matched to patients with placenta previa, but no accreta, by year of delivery. Ultrasound studies with views of the placenta were collected, deidentified, blinded to clinical history, and placed in random sequence. Six investigators prospectively interpreted each study for the presence of accreta and findings reported to be associated with its diagnosis. Sensitivity, specificity, positive predictive, negative predictive value, and accuracy were calculated. Characteristics of accurate findings were compared using univariate and multivariate analyses.
  
  
  RESULTS
  Six investigators examined 229 ultrasound studies from 55 patients with accreta and 56 controls for 1374 independent observations. 1205/1374 (87.7% overall, 90% controls, 84.9% cases) studies were given a diagnosis. There were 371 (27.0%) true positives; 81 (5.9%) false positives; 533 (38.8%) true negatives, 220 (16.0%) false negatives, and 169 (12.3%) with uncertain diagnosis. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 53.5%, 88.0%, 82.1%, 64.8%, and 64.8%, respectively. In multivariate analysis, true positives were more likely to have placental lacunae (odds ratio [OR], 1.5; 95% confidence interval [CI], 1.4-1.6), loss of retroplacental clear space (OR, 2.4; 95% CI, 1.1-4.9), or abnormalities on color Doppler (OR, 2.1; 95% CI, 1.8-2.4).
  
  
  CONCLUSIONS
  Ultrasound for the prediction of placenta accreta may not be as sensitive as previously described.
authors.affiliation: Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Salt Lake City, UT; Department of Obstetrics and Gynecology, Intermountain Healthcare, Salt Lake City, UT.
authors.forename: Zachary S
authors.initials: ZS
authors.lastname: Bowman
authors.affiliation: Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Salt Lake City, UT; Department of Obstetrics and Gynecology, Intermountain Healthcare, Salt Lake City, UT.
authors.forename: Alexandra G
authors.initials: AG
authors.lastname: Eller
authors.affiliation: Department of Radiology, University of Utah Health Sciences Center, Salt Lake City, UT.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Kennedy
authors.affiliation: Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Salt Lake City, UT; Department of Obstetrics and Gynecology, Intermountain Healthcare, Salt Lake City, UT.
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Richards
authors.affiliation: Department of Radiology, University of Utah Health Sciences Center, Salt Lake City, UT.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Winter
authors.affiliation: Department of Radiology, University of Utah Health Sciences Center, Salt Lake City, UT.
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Woodward
authors.affiliation: Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Salt Lake City, UT; Department of Obstetrics and Gynecology, Intermountain Healthcare, Salt Lake City, UT.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Silver
mesh_terms: D000328:Adult; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D016555:Matched-Pair Analysis; D015999:Multivariate Analysis; D010920:Placenta / Q000000981:diagnostic imaging; D010921:Placenta Accreta / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D018615:Ultrasonography, Doppler, Color
keywords: placenta accreta; prenatal diagnosis; sensitivity and specificity; ultrasound