Table A4:

Risk of Bias^a Among Test Accuracy Studies (QUADAS-2 Tool)

	Risk of Bias				Applicability Concerns
Author, Year	Patient Selection	Index Test	Reference Standard	Flow and Timing	Patient Selection	Index Test	Reference Standard
Bianchi et al, 201452	Highb	Low	Low	Highc	Highd	Low	Low
del Mar Gil et al, 201453	Uncleare	Low	Low	Highc	Low	Low	Low
Langlois et al, 201754	Highb	Low	Low	Low	Low	Low	Low
Nicolaides et al, 201255	Highb	Low	Low	Highc	Low	Low	Low
Norton et al, 201556	Highb	Low	Low	Highc	Low	Low	Low
Palomaki et al, 201757	Highb	Low	Low	Highc	Low	Low	Low
Quezada et al, 201558	Highb	Low	Unclearf	Highc	Low	Low	Low
Song et al, 201359	Highb	Low	Low	Highc	Low	Low	Low

Abbreviation: NIPT, noninvasive prenatal testing; QUADAS-2; Quality Assessment of Diagnostic Accuracy Studies.

^aPossible risk of bias levels: low, high, unclear.

^bDid not avoid inappropriate exclusions or had unclear consecutive or random enrolment of patients.

^cInappropriate interval between NIPT and reference standard. Some studies missing or excluded patients in analysis.

^dApplicability concerns because of inappropriate patient exclusions.

^eUnclear patient enrolment and study exclusions.

^fUnclear whether reference standard was interpreted without knowledge of NIPT results.