Christopher 2002.

Study characteristics
Patient sampling	A convenience sample of patients presenting with signs and symptoms was considered by the examining physician as possibly having appendicitis Exclusion criteria: first trimester of pregnancy; obvious requirement for surgical intervention due to presence of a rigid abdomen, hypotension, or other signs of instability Recruitment periods: April 1998 to December 1998; April 2000 to October 2000
Patient characteristics and setting	Age range (mean): 5 to 77 years (32). 52% women. The proportion of patients younger than 10 years was 3% Emergency Department in an urban teaching hospital in Houston, Texas, USA. Single‐centre study Disease spectrum: any suspicion of appendicitis
Index tests	Unenhanced helical CT of the lower abdomen (Picker PQ6000, Picker International; MX8000, Marconi Medical Systems). Slice thickness: 5 mm. Slice interval: not stated. Voltage: 120 kV. mAs product: 250 to 300 mAs
Target condition and reference standard(s)	Appendicitis. Intraoperative findings and histopathological reports in patients who had surgery with or without appendectomy. Patients who did not have surgery were followed up with telephone calls 6 to 8 weeks after presentation to the Emergency Department
Flow and timing	107 patients were included. Of these, 40 had surgery and 31 had appendicitis confirmed histologically. Six patients were lost to follow‐up, and 1 patient withdrew consent before the CT‐scan was obtained, hence 101 patients were included in the analyses
Comparative
Criteria for CT diagnosis of appendicitis	Not reported
Assessors of the CT‐scan	Attending general radiologists
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Did the study avoid inappropriate exclusions?	Yes
Does the study population represent an unselected sample of adults with suspected appendicitis?	Unclear
		Unclear	Unclear
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	No
Is the index test described in sufficient detail to permit its replication?	Yes
Was the analysis based on the initial evaluation of the CT‐scan by the radiologist on call?	Unclear
		High	Unclear
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	No
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
		High	Low
DOMAIN 4: Flow and Timing
Did all patients receive a reference standard?	No
Did all patients receive the same reference standard?	No
Did all patients with a positive CT‐scan have surgery?	No
Did all patients with a negative CT‐scan have clinical follow‐up?	No
Was the choice of reference standard independent of the result of the index test?	No
Were all patients included in the analyses?	No
		High