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Down screening

Down screening Posted by ghada S.

Dear Paul:

How can I calculate risk of Down syndrome from results of quadriple test ??"'As it is not done in our country routinlly"

How the risk is adjusted according to maternal age , gestational age & results of serum screening together??

The cut off value of risk for offering invasive testing is 1 / 150    so does this mean that any woman > 40 years should be offered invasive testing as her risk is 1 /100  even without need for serum screening ??

Please clarify with example 

Thank you

Posted by PAUL A.

Thanks - this is not an adjustment which you can make by hand. You may be asked about risk at different ages. You will not be given the value of the different analytes and expected to calculate risk.


If all you have to go with is maternal age then yes you offer invasive testing based on maternal age. That is what was done in the 1970s before serum screen became available. The benefit of serum screening / ultrasound based screening is that it allows you to refine age-related risk. So a 40 year old with a low NT measurements and a profile of HCG and PAPP-A may have a risk of 1 in 2000 while a 16 year old with increased NT and a different biochem profile will have a risk of 1 in 20. That is the benefit of the current screening approach.