Verweij 2013.

Study characteristics
Patient sampling	Study design: blinded, prospective cohort study. Participants: consecutive pregnant women selected at high risk of fetal aneuploidy presenting for invasive testing. Inclusion criteria: women who sign informed consent, ≥ 18 years old and carrying a singleton pregnancy with a gestational age of at least 10 weeks. Exclusion criteria: multifetal pregnancies, an invasive procedure performed prior to the blood sampling, history or active significant malignancy requiring major surgery or systemic chemotherapy, or language restriction with failure to understand the study information.
Patient characteristics and setting	Number enrolled: 595 pregnant women. Number available for 2 x 2 table: 504 pregnant women (subgroup of 85%). Setting: multicentres in the Netherlands and Sweden. Recruitment period: May 2011 to March 2012. Ethnicity: Caucasian (84.8%), Mediterranean (6%), Asian (3.3%), Afro‐European (1.3%), and other (4.6%). Mean gestational age (± SD; range): 14.0 (± 2.1; 10 to 28) weeks. Mean maternal age (± SD; range): 36.4 (± 4.6; 20 to 47) 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 TMPS (DANSR assay) on Illumina HiSeq 2000 in 96‐plex with FORTE algorithm. Mean fetal fraction DNA (± SD; range): 11.1% (± 4.1%; 4% to 30%). Blood samples for gNIPT were collected just before reference standard. Cutpoint: positive if FORTE risk score ≥ 1%. Commercial test: Ariosa Diagnostics, Inc's test.
Target condition and reference standard(s)	Target condition: T21. Reference standard: fetal karyotype of chorionic villi (54%) or amniotic fluid (46%).
Flow and timing	Blood samples for gNIPT were obtained just prior the invasive procedure (reference standard). gNIPT was a second‐tier test. 75/595 samples were ineligible. 51/520 samples failed the initial TMPS testing. 51/51 samples were repeated with a second aliquot of the first sampling and 35/51 samples obtained a gNIPT results. 16/520 samples failed during sequencing process (no gNIPT result), including 7 samples with low fetal DNA fraction and 9 samples failed laboratory processing or specimen issues.
Comparative
Aim to study	To evaluate the performance of a directed gNIPT method of ccfDNA analysis for fetal T21 by shipping the whole blood samples from Europe to a laboratory in the USA.
Funding source or sponsor of the study	Study funded by Ariosa Diagnostics, Inc. 2 authors are paid employees of Ariosa Daignostics. 1 author is a board member of Ariosa Diagnostics.
Informations about the authors contacted	Author was contacted on: 22 April 2016. Reply received on: 25 April 2016.
Notes
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?	No
		High	Low
DOMAIN 2: Index Test TMPS
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?	No
		High