Busel 1989.

Study characteristics
Patient sampling	Type of study: retrospective. Consecutive or random sample: unclear.
Patient characteristics and setting	Sample size: 38. Females: not stated. Age: not stated. Presentation: Inclusion criteria: People undergoing common bile duct exploration for common bile duct stones. Setting: Surgery and Gastroenterology Departments, Chile.
Index tests	Index test: ultrasound. Technical specifications: sectorial transducer 3.5 MHz (manufacturer not stated). Performed by: not stated. Criteria for positive diagnosis: echogenic image with or without acoustic shadow In the common bile duct.
Target condition and reference standard(s)	Target condition: common bile duct stones. Reference standard: surgical exploration of common bile duct. Technical specifications: not applicable. Performed by: surgeons. Criteria for positive diagnosis: surgical exploration of common bile duct.
Flow and timing	Number of indeterminates for whom the results of reference standard was available: not stated. Number of participants who were excluded from the analysis: not stated.
Comparative
Notes	Attempted to contact the authors in June 2013. Received no replies.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Unclear
		High	High
DOMAIN 2: Index Test All tests
Were the index test results interpreted without knowledge of the results of the reference standard?	Unclear
If a threshold was used, was it pre‐specified?	Yes
		High	Low
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
		High	High
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Unclear
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	Unclear
		Unclear