False Positive Phrase?!?!?!

[stephie4]

I don't understand this 'false positive' phrase. (and its becoming a pet peeve of mine to hear it)

even if the blood work comes back as 1/10 chance of having downsyndrome, its not a 'positive' or 'negative' or absolute in any way.  its just a precentage of odds.  
Is there something I'm missing, is there different blood tests that say a definite yes or no?

When my dr. saw the spot in the heart, and said it brought my downs chances odds down up to 1 in 100, and then amnio cleared me, the heart marker wasn't a false positive at all.  he never in anyway said, with this marker its 100% positive that baby has downs. Nor with my blood work coming back as 1 in 6,200  did he say it was negative for downs, just that they were good numbers.

[AZ Angie]

To add.  It would porbably be more appropriate to say tha you had a "false alarm" -- Thank God!!

[AZ Angie]

I think when people say it was "Positive" test, they ar borrowing part of the medical jargon, but not the complete term.  In medical term, the test is a screening test only.  It screens out low risk patients, and screens IN high risk patients -- for further testing.  When they say you had a "Positive screen" it means that you go on to the next round of testing (and your insurance will pay for it if, and only if you have a positive screen).  That's where the "Positive" comes from.  It, in no way, means that you are actually positively abnormal, just slightly higher risk, and requiring more investigation that is cost worthy. ....Just another example of how the insurance industry actually drives medicine....ugh!
Angie

[pcarsey]

As jifnif was saying- I was told they look for more then one marker after they find the first one. then they take into consideration ALL the factors!

[jifnif]

i think in the case of these tests a false positive is used when it seems that the marker or results yield a positive result but it cannot be definitely proven to be positive.  so when you find out that your child did not have downs, the test was considered a false positive.  it in fact lead you to believe that you might be having a downs baby or a higher chance of it...the marker is positive.  this is not a good way to measure the chances of a downs.  you will probably need more than one marker or test to actually have a positive test.  hope that is not to confusing.  

[kellym]

You're right Steph. It's a percentage. Once your #'s hit in the danger zone  your percentage is considered + or -.  BUT, sometimes LMP can be off a couple of days or "O" and it throw the test way off. Another thing is age. All of the equasion (sp) can be perfect and then throw the age factor in and that could make the determining factor. I know it's annoying. We had out of town friends call to say their test was + and they were freaking out but they didn't have all the facts.