title: Assessment of the alveolar-arterial oxygen gradient as a screening test for pulmonary embolism in pregnancy.
abstract: OBJECTIVE
  The objective of the study was to determine whether the alveolar-arterial (A-a) oxygen gradient is an adequate screening test for pulmonary embolism (PE) in pregnancy and postpartum.
  
  
  METHODS
  A chart review was performed at Tampa General Hospital. Patients who had a workup for a PE consisting of a computed tomography pulmonary angiogram and an arterial blood gas from 2002 to 2009 were included in the analysis. Sensitivity, specificity, and negative and positive predictive values were calculated. Additionally, common clinical signs and symptoms were assessed for their ability to accurately predict PE.
  
  
  RESULTS
  Of 102 patients, there were 13 PEs (2 antepartum and 11 postpartum). The best sensitivity, specificity, and negative and positive predictive values for A-a gradients were 76.9%, 20.2%, 80.0%, and 11.5%, respectively.
  
  
  CONCLUSIONS
  The A-a gradient is a poor screening test for PE in pregnancy and postpartum. Suspicion of PE should prompt early imaging studies to rapidly make the diagnosis and begin treatment.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa, FL 33606, USA.
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Deutsch
authors.forename: Pamela
authors.initials: P
authors.lastname: Twitty
authors.forename: Katheryne
authors.initials: K
authors.lastname: Downes
authors.forename: Michael T
authors.initials: MT
authors.lastname: Parsons
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008403:Mass Screening; D010100:Oxygen / Q000378:metabolism*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis*; D011650:Pulmonary Alveoli / Q000378:metabolism*; D011655:Pulmonary Embolism / Q000175:diagnosis*; D011659:Pulmonary Gas Exchange; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D010100:Oxygen