Sepulveda 2013.

Study characteristics
Patient Sampling	Study design: retrospective observational study Recruitment: hospital records of patients who were diagnosed with holoprosencephaly pre‐ or postnatally at the study centre during the study period were reviewed Study start and end date: January 2004 to December 2012
Patient characteristics and setting	Setting: tertiary care facility (Fetal Medicine Center of Clinica Las Condes) Region(s) and country/countries from which participants were recruited: Santiago, Chile Sample size: 11,058 Study eligibility criteria: cases of holoprosencephaly that had sonographic evaluation in the first trimester in the study centre Number of participants with the target condition: 1 Population type: unselected population Prior testing: nuchal translucency measurement at the time of the first‐trimester scan
Index tests	Type: two‐stage screening (data were only reported for the first‐trimester scan) First‐trimester scan: Timing (weeks and days gestation): 11 to 13 weeks’ gestation Ultrasound scanning protocol: detailed Cardiac screening: not reported Mode of examination: primary transabdominal, transvaginal if necessary Single or multiple operators: not reported Staff qualification and/or operator experience level: not reported Second‐trimester scan: Data to construct 2 x 2 tables could not be extracted or derived from the report
Target condition and reference standard(s)	Target condition(s): holoprosencephaly Definitions used for major and minor congenital abnormalities: not reported Reference standard (live birth): pregnancy and neonatal outcomes were obtained from hospital records, contacting the referring obstetrician or patients themselves in cases delivering in another institution Reference standard (fetal or neonatal demise): not reported Postnatal follow‐up duration: not reported
Flow and timing	Eligible patients: 11,068 Exclusions (study investigator): none reported Exclusions (review team): 10 (abnormal karyotype)
Comparative
Notes	Funding source: this work was supported by an unrestricted research grant from the Sociedad Profesional de Medicina Fetal ‘Fetalmed’, Chile
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Yes
Could the selection of patients have introduced bias?		Low risk
Are there concerns that the included patients and setting do not match the review question?			High
DOMAIN 2: Index Test (First‐trimester scan)
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
Could the conduct or interpretation of the index test have introduced bias?		Low risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 2: Index Test (First + second‐trimester scan)
DOMAIN 2: Index Test (Single second‐trimester scan)
DOMAIN 3: Reference Standard
Is the reference standard likely to correctly classify anomalies that are externally visible, present with clinically relevant symptoms shortly after birth, or that are considered to be lethal/incompatible with life?	Yes
Is the reference standard likely to correctly classify anomalies that may present after discharge from postnatal care?	Unclear
Were the reference standard results interpreted without knowledge of the results of the index test?	No
Could the reference standard, its conduct, or its interpretation have introduced bias?		Unclear risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			Low concern
DOMAIN 4: Flow and Timing
Did all live‐born infants receive a reference standard?	Yes
Did all live‐born infants receive the same reference standard?	No
Did all cases of fetal or perinatal loss receive the reference standard (including termination of pregnancy, intra‐uterine death, stillbirth, perinatal mortality)?	Unclear
Were all patients included in the analysis?	Yes
Could the patient flow have introduced bias?		Unclear risk