A screening test is not a diagnosis
The single most important distinction in this tool.
A screening test sorts people into higher and lower probability. A diagnostic test tells you whether the condition is present. Cell-free DNA screening, first-trimester combined screening and the quad screen are all screening tests. Amniocentesis and chorionic villus sampling are diagnostic.
ACOG guidance is explicit that cell-free DNA testing is not equivalent to diagnostic testing, and that a patient with a positive result should be offered genetic counselling, a detailed ultrasound and the opportunity for diagnostic testing to confirm the result.
The practical ruleNo irreversible decision should be made on the basis of a screening result alone. If anyone suggests otherwise, ask for a diagnostic test first.
What a normal result cannot promisePart 4 sets out what is left after every test comes back normal: about 1 in 33 babies is born with a birth defect, four out of five major birth defects have no known cause, and most of them are not on any screening panel. See Part 4, The perfect baby.
Where this comes from:
145. American College of Obstetricians and Gynecologists' Committee on Practice Bulletins-Obstetrics, Committee on Genetics, Society for Maternal-Fetal Medicine. Screening for fetal chromosomal abnormalities. ACOG Practice Bulletin No. 226. Obstet Gynecol. 2020;136(4):e48-e69.
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This page is educational. It supports the conversation with your own clinicians. It is not consent to any treatment, and it cannot assess you. If you are worried about a symptom now, see urgent warning signs.