AFP Profile Four

By including dimeric inhibin-A as a fourth biochemical marker for Down syndrome screening, FBR makes it possible for prenatal care providers to screen for this disorder more accurately than ever before.

DIMERIC INHIBIN-A: Frequently Asked Questions About the AFP Profile Four...

What is dimeric inhibin-A (DIA)?

DIA is a glycoprotein of placental origin similar to hCG. Levels in maternal serum remain relatively constant through the 15th-18th weeks of pregnancy.

What is DIA's relationship to Down syndrome?

Maternal serum levels of DIA are twice as high in pregnancies affected by Down syndrome as in unaffected pregnancies. DIA is as effective a marker for Down syndrome as hCG, yet provides information that hCG and the other markers do not.

What is the effect of DIA on Down syndrome screening performance?

In the AFP Profile Four, DIA is used with three other analytes and maternal age to characterize more accurately Down syndrome risk. Screening programs can use DIA either to increase the Down syndrome detection rate while maintaining the screen-positive rate, OR to decrease the screen-positive rate while maintaining the detection rate.

How does this compare to triple marker screening?

In our experience in Maine, the use of DIA lowered the screen-positive rate from 4.7% to 2.9%, a reduction of nearly 40%. The Down syndrome detection rate is expected to remain steady at 67%. Alternatively, screening programs can use DIA to increase detection up to 76%, while holding the screen positive rate at about 5%.

Will use of the AFP Profile Four change how screening should be offered to patients?

Not at all. Screening should still be offered at 15-18 weeks. No special conditions are required for blood draws or sample handling. The AFP Profile Four report is similar to the AFP Profile report, except that the DIA level and its MoM are included and are incorporated into the risk calculation for Down syndrome.

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