NIPT Accuracy – Positive Predictive Value Calculator

~ Trisomy 18 and Trisomy 13 Screening  ~

Check your Non Invasive Prenatal Test (NIPT) accuracy with the
Positive Predictive Value Calculator

by Dr Marty McCaffrey, neonatologist
Taken from a SOFT Facebook Group post 10/23/2015

For those of you expectant mothers out there who may have had a blood test to determine if your baby has trisomy 21, 13, or 18, understand that test is just a SCREENING test. It is NOT diagnostic. It is not marketed as diagnostic, no matter what a healthcare provider might tell you. The link below, developed by concerned obstetricians and genetic counselors, is to a calculator which will tell you how accurate your positive (positive predictive value) or negative (negative predictive value) result is. You will be surprised. Depending on your age and the particular chromosomal disorder, this test (NIPT) is not much better than a coin flip.

NIPT Predictive Value Calculator  (link)

The NIPT/cfDNA Performance Caclulator is a tool to quickly and easily understand the positive predictive value of a prenatal test given the condition, maternal age, specificity of the test, and sensitivity of the test. This web based PPV calculator was made by Sound Information Services LLC.

Comments from parents:

It also bears mentioning that screening during pregnancy is optional. It’s usually ordered as if it is required, particularly for women over 35, and rarely are things like false negatives or positives discussed. We were fortunate to have a midwife who provided extensive information on all available screening and left decisions up to us. I will be forever thankful that I spent almost my entire pregnancy joyously anticipating our daughter’s arrival instead of in sadness, worry, or fear. That’s just me, but we should all have that choice.

  I was advised to have an abortion before we even had the amnio! In our case the NIPT was sadly correct (we carried her anyway) but I think a lot of OB providers don’t even get that this is not diagnostic.