Sehnert 2011.

Study characteristics
Patient sampling	Study design: blinded retrospective study (archived maternal plasma samples). Participants: pregnant women selected from a high risk of fetal aneuploidy population. Inclusion criteria: pregnant women age 18 years or older with singleton or multifetal pregnancy. Exclusion criteria: not reported.
Patient characteristics and setting	Number enrolled: overall: 1014 pregnant women including 71 women selected on 435 for the training set (not shown in the present review) and 48 women selected on 575 for the test set. Number available for 2 x 2 table: 47 (subgroup of 8%). Setting: 13 centres in USA. Recruitment period: January 2010 to June 2010. Ethnicity: Caucasian (62.7%), Hispanic (16.5%), Asian (6.2%), multiethnic (5.2%), Afro‐American (4.0%), Native American (0.9 %) and other or not specified (1.8%). Mean gestational age (range): 15.4 (10.6 to 28.4) weeks. Mean maternal age (± SD; range): 34.2 (± 8.22; 18 to 46) years. Relevant tests carried out prior to index test: ultrasonography (nuchal translucency measurement) or biochemical screening or both. Language of the study: English.
Index tests	gNIPT by MPSS on Illumina Genome Analyzer IIx sequencer in uniplex. Fetal fraction DNA: not reported. Blood samples for gNIPT were collected before reference standard. Cutpoint prespecified with the training set: 1) positive if NCV > 4 for autosomes. There is a "no call zone" between 2.5 and 4 considering as gNIPT positive result for the present review. 2) positive if NCV for Chrom. Y < ‐2.0 SDs from the mean of male samples and if NCV for Chrom. X < ‐3.0 SDs from the mean of female samples for 45,X. Commercial test: Verinata's prenatal test.
Target condition and reference standard(s)	Target conditions: T21, T18, T13 and 45,X. Reference standard: fetal karyotype of chorionic villi (58,3%) or amniotic fluid (41.7%).
Flow and timing	Blood samples for gNIPT were obtained prior to the invasive procedure (reference standard). gNIPT was a second‐tier test. 895/1014 samples were not selected for sequencing. 71/119 samples were selected for the training set (not shown in the present review). 1/48 sample from twin gestation in the test set was removed from the final analysis. No repeated test reported.
Comparative
Aim to study	To develop and test an optimised algorithm from MPSS data and demonstrated the potential universality of the sequence tag mapping and chromosome quantification method for the detection of multiple chromosomal abnormalities.
Funding source or sponsor of the study	Study funded by Illumina (formerly Verinata Health). The funding organizations played a direct role in the design of the study, the choice of enrolled patients, the review and interpretation of data, and the preparation and final approval of the manuscript.
Informations about the authors contacted	No need for further contact.
Notes
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?	Yes
Did the study avoid inappropriate exclusions?	No
		High	Low
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?	Yes
		Low	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?	Yes
		Low