title: Prospective comparison of the Alvarado score and CT scan in the evaluation of suspected appendicitis: a proposed algorithm to guide CT use.
abstract: BACKGROUND
  Although computed tomography (CT) has reduced negative appendectomy rates, its radiation risk remains a concern. We compared the performance statistics of the Alvarado Score (AS) with those of CT scan in the evaluation of suspected appendicitis, with the aim of identifying a subset of patients who will benefit from CT evaluation.
  
  
  METHODS
  We performed prospective data collection on 350 consecutive patients with suspected appendicitis who were evaluated with CT scans. The AS for each patient was scored at admission and correlated with eventual histology and CT findings. The sensitivity, specificity, and positive likelihood ratios were determined for various AS and for CT scan. The AS ranges that benefitted most from CT evaluation were determined by comparing the positive likelihood ratios of CT scan with each of the AS cutoff values.
  
  
  RESULTS
  The study included 134 males (38.3%) and 216 females (61.7%). The overall prevalence of appendicitis was 44.3% in the total study population; 37.5% in females and 55.2% in males. There were 168 patients (48%) who underwent surgery, with a negative appendectomy rate of 7.7%. Positive likelihood ratio of disease was significantly greater than 1 only in patients with an AS of 4 and above. An AS of 7 and above in males and 9 and above in females has a positive likelihood ratio comparable to that of CT scan.
  
  
  CONCLUSIONS
  Evaluation by CT is beneficial mainly in patients with AS of 6 and below in males and 8 and below in females. We propose an objective management algorithm with the AS guiding subsequent evaluation.
authors.affiliation: Department of General Surgery, Singapore General Hospital, Singapore. Electronic address: tanwinson156@hotmail.com.
authors.forename: Winson Jianhong
authors.initials: WJ
authors.lastname: Tan
authors.affiliation: Centre for Qualitative Medicine, DUKE NUS Graduate Medical School, Singapore.
authors.forename: Sanchalika
authors.initials: S
authors.lastname: Acharyya
authors.affiliation: Department of General Surgery, Singapore General Hospital, Singapore.
authors.forename: Yaw Chong
authors.initials: YC
authors.lastname: Goh
authors.affiliation: Department of General Surgery, Singapore General Hospital, Singapore.
authors.forename: Weng Hoong
authors.initials: WH
authors.lastname: Chan
authors.affiliation: Department of General Surgery, Singapore General Hospital, Singapore.
authors.forename: Wai Keong
authors.initials: WK
authors.lastname: Wong
authors.affiliation: Department of General Surgery, Singapore General Hospital, Singapore.
authors.forename: London Lucien
authors.initials: LL
authors.lastname: Ooi
authors.affiliation: Department of General Surgery, Singapore General Hospital, Singapore.
authors.forename: Hock Soo
authors.initials: HS
authors.lastname: Ong
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001062:Appendectomy / Q000706:statistics & numerical data; D001064:Appendicitis / Q000175:diagnosis* / Q000601:surgery; D003661:Decision Support Techniques; D003937:Diagnosis, Differential; D005189:False Positive Reactions; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D019564:Unnecessary Procedures / Q000706:statistics & numerical data; D055815:Young Adult