title: Derivation of a clinical guideline for the assessment of nonspecific abdominal pain: the Guideline for Abdominal Pain in the ED Setting (GAPEDS) Phase 1 Study.
abstract: OBJECTIVE
  The purpose of this study was to identify a clinical guideline for the evaluation of nonspecific abdominal pain (NSAP) using history, physical examination, laboratory analysis, acute abdominal series (AAS) radiographs, and nonenhanced helical computed tomography (NHCT) clinical predictor variables (CPVs).
  
  
  METHODS
  The setting of this study was at an urban emergency department (ED) with 70,000 yearly visits.
  
  
  METHODS
  This is an institutional review board-approved, prospective, observational study. The primary outcome variable was urgent intervention (UI), defined as a diagnosis requiring surgical or medical treatment to prevent death or major morbidity. Subjects underwent prompted history, physical, laboratory studies, AAS, and NHCT and were followed up to 6 months for ultimate diagnosis and outcome. CPVs were subjected to classification and regression tree analysis.
  
  
  RESULTS
  One hundred sixty-five subjects were analyzed. Thirteen percent of subjects required UI within 24 hours of presentation; an additional 34% underwent elective interventions that mitigated morbidity or mortality. Four guideline models were generated. Model 1 consisted of history and physical, with a sensitivity of 25%, a specificity of 92%, a positive likelihood ratio of 3.17, and a negative likelihood ratio of 0.81. Model 2 consisted of model 1 with laboratory, with a sensitivity of 39%, a specificity of 88%, a positive likelihood ratio of 3.25, and a negative likelihood ratio of 0.69. Model 3 consisted of model 2 with AAS, with a sensitivity of 56%, a specificity of 81%, a positive likelihood ratio of 2.94, and a negative likelihood ratio of 0.54. Model 4 comprised all inputs, including NHCT, with a sensitivity of 92%, a specificity of 90%, a positive likelihood ratio of 9.2, and a negative likelihood ratio of 0.089. NHCT was the single most accurate CPV for UI.
  
  
  CONCLUSIONS
  No clinical guideline was identified exclusive of NHCT that possessed adequate sensitivity for exclusion of UI. NHCT is a rational choice for decision support in the evaluation of NSAP and is likely the single most useful diagnostic adjunct available to augment the clinical evaluation.
authors.affiliation: Department of Emergency Medicine, Brooke Army Medical Center/San Antonio Uniformed Services Health Education Consortium, Fort Sam Houston, TX 78234, USA. robert.gerhardt@us.army.mil
authors.forename: Robert T
authors.initials: RT
authors.lastname: Gerhardt
authors.forename: Brian K
authors.initials: BK
authors.lastname: Nelson
authors.forename: Sean
authors.initials: S
authors.lastname: Keenan
authors.forename: Leah
authors.initials: L
authors.lastname: Kernan
authors.forename: Andrew
authors.initials: A
authors.lastname: MacKersie
authors.forename: Michael S
authors.initials: MS
authors.lastname: Lane
mesh_terms: D000006:Abdomen, Acute / Q000000981:diagnostic imaging; D015746:Abdominal Pain / Q000175:diagnosis*; D000328:Adult; D004635:Emergency Medicine / Q000379:methods* / Q000592:standards*; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008487:Medical History Taking; D008875:Middle Aged; D008962:Models, Theoretical; D010043:Outcome and Process Assessment, Health Care; D010808:Physical Examination; D017410:Practice Guidelines as Topic; D011446:Prospective Studies; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013781:Texas; D036542:Tomography, Spiral Computed