Kim 2012.

Study characteristics
Patient sampling	Patients aged 15 to 44 years were referred for CT examination by Emergency Department physicians due to clinically suspected appendicitis. Patients with prior appendectomy, pregnant women, patients with allergy to intravenous contrast material, patients with impaired renal function, and patients who had prior cross‐sectional imaging tests to evaluate the presenting symptoms were excluded. Recruitment period: September 2009 to January 2011 Included patients were randomised to receive low‐dose or standard‐dose intravenous contrast‐enhanced CT
Patient characteristics and setting	Low‐dose CT: age quartiles (median): 22 to 36 years (29); 62% women Standard‐dose CT: age quartiles (median): 22 to 37 years (30); 59% women Emergency Department and Department of Radiology in Seoul, Korea. Single‐centre study Disease spectrum: any suspicion of appendicitis
Index tests	Intravenous contrast‐enhanced abdominal CT using 16‐, 64‐, or 256‐slice CT‐scanners. Slice thickness: 2 to 5 mm. Slice interval, voltage, and mAs product: not stated. Unclear whether the CT‐protocol included the entire abdomen and pelvis. Manufacturer of CT‐scanners and model name are not reported Low‐dose CT: intended radiation dose 2 mSv Standard‐dose CT: intended radiation dose 8 mSv
Target condition and reference standard(s)	Appendicitis. The reference standard had 3 components: intraoperative findings in patients who had surgery but no appendectomy, histological examination of the resected appendix in patients who had an appendectomy, and follow‐up in patients who did not have surgery. Follow‐up was based on review of medical records and telephone interviews 3 months after presentation
Flow and timing	1035 patients were eligible for inclusion, 444 were randomised to have low‐dose CT, and 447 were randomised to have standard‐dose CT In the low‐dose CT group, 189 patients had surgery, 172 had appendectomy (166 had appendicitis), 249 had follow‐up, and 6 patients were lost to follow‐up In the standard‐dose CT group, 195 patients had surgery, 186 had appendectomy (180 had appendicitis), 246 had follow‐up, and 6 patients were lost to follow‐up
Comparative
Criteria for CT diagnosis of appendicitis	Appendix diameter > 6 mm, abscess or phlegmon in the right iliac fossa, appendicolith, periappendiceal fat stranding, abnormal appendix wall enhancement, thickened appendix wall The radiologist graded the likelihood of appendicitis on a 5‐point scale. 1: definitely absent, 2: probably absent, 3: indeterminate, 4: probably present, 5: definitely present. In the accuracy analyses, patients with grade 3 to 5 likelihood of appendicitis were considered CT‐positive
Assessors of the CT‐scan	During daytime: 3 expert radiologists. During after‐hours: on‐call radiologists with various levels of expertise
Notes	The low‐dose group and the standard‐dose group enter the meta‐analyses as 2 separate studies
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Did the study avoid inappropriate exclusions?	Yes
Does the study population represent an unselected sample of adults with suspected appendicitis?	Unclear
		High	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?	Yes
Is the index test described in sufficient detail to permit its replication?	No
Was the analysis based on the initial evaluation of the CT‐scan by the radiologist on call?	Unclear
		Low	High
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?	Yes
Did all patients receive the same reference standard?	No
Did all patients with a positive CT‐scan have surgery?	Unclear
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?	Yes
		High