title: Probability of appendicitis before and after observation.
abstract: OBJECTIVE
  To examine patients with abdominal pain for changes in probability of appendicitis during observation.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  University-affiliated community hospital.
  
  
  METHODS
  252 patients with abdominal pain who were examined underwent short-term (10.4 hours) observation (95% confidence interval [CI], 8.7, 12.1) before the decision to operate during a one-year period. Alvarado's scoring system and a probability-of-diagnosis nomogram were used to assign scores and estimate probability of appendicitis.
  
  
  RESULTS
  In the study group, mean score of patients with appendicitis increased after observation from 6.8 (95% CI, 6.2, 7.4) to 7.8 (95% CI, 7.3, 8.3), corresponding to a change in probability of appendicitis from 50% to 65%. Mean score of patients without appendicitis decreased from 3.8 (95% CI, 3.5, 4.1) to 1.6 (95% CI, 1.58, 1.62), corresponding to a change in probability from 35% to 22%. The difference between mean scores for patients with and without appendicitis increased from 2.6 (95% CI, 2.0, 3.2) to 6.2 (95% CI, 6.15, 6.25) during observation. The study group initially had intermediate probability of appendicitis (score, 4.35; 95% CI, 4.04, 4.66) compared with high probability for patients who went directly to surgery after their initial evaluation (63 patients; score, 7.59; 95% CI, 7.05, 8.73) and low probability for patients with abdominal pain who were sent home after their initial evaluation without observation or surgery (2,097 patients; score, 1.87; 95% CI, 1.48, 2.26).
  
  
  CONCLUSIONS
  In this group of patients with intermediate initial probability of appendicitis, observation improved the ability to distinguish patients with from those without appendicitis.
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington.
authors.forename: L
authors.initials: L
authors.lastname: Graff
authors.forename: M J
authors.initials: MJ
authors.lastname: Radford
authors.forename: C
authors.initials: C
authors.lastname: Werne
mesh_terms: D015746:Abdominal Pain / Q000175:diagnosis; D000293:Adolescent; D000328:Adult; D001064:Appendicitis / Q000175:diagnosis*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003951:Diagnostic Errors; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010808:Physical Examination; D011336:Probability; D012189:Retrospective Studies