Chiu 2011.

Study characteristics
Patient sampling	Study design: blinded, case‐control study (1:5) from a prospective cohort and archived plasma. Participants: pregnant women with clinical indications for invasive procedure, mixed risk (mostly high risk (> 1/300 at traditional screening test), intermediate risk (between 1/300 and 1/1000) or other risk factors). T21 and non T21 pregnancies matched for gestational ages. Inclusion criteria: singleton pregnancies. Exclusion criteria: multifetal pregnancies.
Patient characteristics and setting	Number enrolled: 824 pregnant women. Number available for 2 x 2 table: 753 (8‐plex) (subgroup of 91%). Setting: 10 centres in Hong Kong, the Netherlands, and UK. Recruitment period for the prospective cohort: October 2008 to May 2009. Recruitment period for the archived plasma samples collection: October 2003 to September 2008. Ethnicity: not reported. Median gestational age: 13.1 weeks. Median maternal age: 35.4 years. Relevant tests carried out prior to index test: ultrasonography (nuchal translucency measurement) and biochemical screening. Language of the study: English.
Index tests	gNIPT by MPSS on Illumina Genome Analyzer II in 8‐plex and 2‐plex (not reported in the present review). Median fetal fraction DNA (interquartile 1 and 3): male euploid: 15.2% (10.6% and 19.1%), archived samples: 14.7%, and prospective samples: 15.4%. Blood samples for gNIPT were collected before reference standard. Cutpoint: positive if Z score > 3. Commercial test: Sequenom's test.
Target condition and reference standard(s)	Target condition: T21. Reference standard: fetal karyotype of chorionic villi or amniotic fluid.
Flow and timing	Blood samples were obtained prior to the invasive procedure (reference standard). gNIPT was a second‐tier test. 60/824 samples were excluded before sequencing process (2 twin pregnancies, 12 without karyotype and 46 failed quality control for blood sampling). 11/764 samples failed quality control during sequencing process (no gNIPT result). 96/753 samples were also used for reference controls (8‐plex). No repeated test reported.
Comparative
Aim to study	To validate the diagnostic performance and practical feasibility of massively parallel genomic sequencing for the non‐invasive prenatal assessment of trisomy 21 in pregnant women who had undergone conventional screening and were clinically indicated for definitive testing.
Funding source or sponsor of the study	Study sponsored by Sequenom, Inc. Some authors have filed patent applications on gNIPT (part of this patent has been licensed to Sequenom, Inc).
Informations about the authors contacted	No need for further contact.
Notes	Data from 2‐plex sequencing were excluded from the present review to avoid double counting. We kept data from 8‐plex because it is the method most likely to be used for routine testing.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Was a case‐control design avoided?	No
Did the study avoid inappropriate exclusions?	No
		High	High
DOMAIN 2: Index Test MPSS
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
		Low	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
		Unclear	Low
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all analysed patients receive the reference standard?	Yes
Were all patients included in the analysis?	No
		High