Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1151 page)

   NIPS is not able to distinguish specific forms of aneuploidy, an extrachromosome versus a Robertsonian translocation, or low-level mosaicism.

   Uninformative test results due to insufficient isolation of cell-free fetal DNA could lead to a delay in diagnosis or eliminate the availability of information for risk assessment.

   Providers should check turnaround time before offering patients NIPS if timing is important for reproductive decision making.

   NIPS does not replace the utility of a first-trimester ultrasound examination.

   Limited data are currently available on the use of NIPS in twins and higher-order pregnancies.

   NIPS has no role in predicting late-pregnancy complications.

   More information available: GREGG et al. ACMG statement on noninvasive prenatal screening for fetal aneuploidy.

PRENATAL SCREENING, SECOND-TRIMESTER SCREENING (MATERNAL SERUM SCREENING; QUAD SCREEN)
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   Definition

   Performed between 15 and 22 weeks of gestation, the quadruple screen combines maternal age plus four serum biochemical markers: hCG, inhibin A, AFP, and unconjugated estriol to assess the risk of trisomy 21 and trisomy 18.

   Use

   Risk assessment for trisomy 21 (Down syndrome), trisomy 18, and open neural tube defects

   Interpretation

   Trisomy 21 profile typically has high levels of hCG and inhibin A with low levels of AFP and unconjugated estriol.