AFP test and false positives - Mothering Forums

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#1 of 14 Old 02-04-2003, 12:49 PM - Thread Starter
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I had my second prenatal visit yesterday and although I should only be 13 weeks according to my last period, the doc says I am measuring more like 15 weeks. At my first visit they thought I was a few weeks further along as well. I declined to have a dating us done on the first visit, but my doc told me that if I want to have the AFP screening test done it has to be in the 16th week so I need to get a correct date. She also told me the AFP test returns a false positive for things like down syndrome, spina bififda and others at least 10% of the time. I was just going to skip it altogether, but dh wants to have it done. So now I have an appt. on Thurs for an us and then will be having the blood test done soon thereafter. I guess I am just wondering how many of you have or will have this screening done and have you experienced a false positive? I had the test with dd and it was negative, but I was not aware of the chances of innacuracy the first time, or I might have skipped it then too.
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#2 of 14 Old 02-04-2003, 01:09 PM
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We had a false-positive on the triple screen, which includes the AFP test, I think...and also measures levels of some estrogens.

Because of my age, what would be only marginal readings in a younger woman turned into an absolute!! Insurance insists that you go for an amnio or a level 2 ultrasound, and to get counseling, blah blah blah... all highly useful if your babe did have problems, but our Down syndrome girl (according to the test results) is now a highly gifted 6 yr old...

If I got pregnant again, at my age, I'm pretty sure they'd bully me into it again...I was adamant at the ultrasound that they look as carefully as they could at the anatomic areas that would be of concern if she DID have Downs. We weren't going to abort, and I wanted to be prepared for heart surgery, kidney problems, whatever. The doc kept trying to get me in for an amnio, but I wouldn't risk it...

My midwife was kinda pissed about the whole thing...but I ended up seeing it as a bump in the road.
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#3 of 14 Old 02-04-2003, 02:08 PM
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I was told by the perinatologist where I had a level II ultrasound (UNC women's hospital) that in women 35 and over, the AFP false positive rate is 25%. I was amazed that it was that high. Almost surprises me that they'd even offer it with that kind of false-pos. rate! That reasured me that I had made the right choice in declining it for this second time just as I did with my first child (though I was under 35 at the time).
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#4 of 14 Old 02-04-2003, 03:15 PM
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I didn't have an AFP test with either of my girls...I knew I wouldn't abort, and I also knew about the high false positive rate...I just didn't want that kind of stress throughout the rest of my pregnancy (and I'm the type to stress about it!).

My best friend had the AFP test with both of her girls. With her first, she came out with a slightly increased risk of a Down's baby (dd1 was fine). She came out with a very increased risk of a Down's baby with her second pregnancy - her second daughter was also fine.

But...she is the type not to stress too much about it...she just figured they were both false positives (and she was right). But then - why have the tests anyway? She never did have an amnio with either, as she also wouldn't have aborted.

It's a very personal decision...good luck with whatever you decide.
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#5 of 14 Old 02-04-2003, 04:10 PM
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I lived in CA at the time I was prengant with my son and was informed that the AFP (triple marker) test was a state req. I was 24 at the time and living a healty lifestyle.
I went in at 16weeks for the test and had a call less than a week later from my OBGYN that my results were extremely low for 2 of the 3 tests. THere was a 1 in 80 chance of Nathan having Trisomy 18 (severeve physical and mental retardation and life expectancy of 2). The odds were the same as thatof a 44 year old woman. Which made us think if we could handle that stiuation emotionally or financially.
We did gentic counseling where I was told my the counselor that I was due in February and had concieved in May. I was due in March and had concieved in June(thank you very much!). I told him he was wrong but he told me he couldn't change the file.
I had an amnio and a level 2 ultrasound, only to show that Nate was perfect!
My doctor said that the lab's equipment could be flawed or old! I also had a friend who's friend was pregnant and had the test with bed results.
The amount of error is huge. Just be educated and aware that some facilities are not operating by the standards that they should be. Which is unfortunate for those of us who are using them.
Good luck! And go with your gut! If everything feels fine then it probably is!
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#6 of 14 Old 02-04-2003, 04:42 PM
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#7 of 14 Old 02-04-2003, 06:35 PM
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I declind the afp/ triple screens but did want an u/s to look for the possibility of spina-bifada, etc. The thing was that my insurance required the U/S to be "medically necessary" and me just wanting to rule out abnormalities wasn't good enough! We had to say it was to ck for dates ( I was measuring big, but it was bcz I am big, not the baby).
My thinking is that the blood work is cheaper than routine U/S for everybody. So they get to pass over a group of women who have low statistical risk for "medically indicated" U/S. If your AFP comes back with a high risk, you get approved for your U/S. My confusion is that the U/S seemed alot more reliable to me than the triple screens, and not as invasive or risky as an amnio for sure.
Well, luckily I got what I wanted & got to avoid the worry of a false positive. good luck, Maria
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#8 of 14 Old 02-04-2003, 06:59 PM
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i had a false positive with my son, and i had an amnio which showed that everything was fine. i had another false positive with this pg, but this time i decided to forego the amnio. both midwives at my birthing center looked at the u/s, and said that everything looks fine, so i'm not worrying about it.
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#9 of 14 Old 02-04-2003, 07:10 PM
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I don't think the 16th week rule is absolutely true. I think you can have the test until the 18th week. After that it gets fuzzy.

however, if I may share my feelings, unless you're planning on terming the pg after knowing the results, or want to plan (and potentially worry) for the rest of your pg, it's up to you to take the test. Perosnally, I declined to test b/c the chances for false pos and false neg made it not worth it to me - and i have no intention of terming the pg, and I'd rather see what happens when the babe is born. concentrate on gestational vibes now, concentrate on taking care of a babe, in what ever state, after they arrive.

i know some folks would rather know, but after discussing w/my doc, there wasn't much prep work we could do if we knew before hand, and the potential for a bad outcome due to worry and distress was probably more harmful.

i think your doc may just be trying to get you to verify the dates (get an u/s) for his sake - your uterus could just be larger, and the babe inside the size you expect. but it makes the docs feel good to have their tests. Unless your period was that irregular, it's pretty unlikely (and a hard sell, imho) to be 2 weeks ahead - more likely to be 4 weeks, yk? But, if you know that's not the case, then you know.

follow your heart.

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#10 of 14 Old 02-04-2003, 07:39 PM
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We always decline the AFP because of the false positive reading.. My ob told me it was something like 40 %, and of those false positives something like 60 percent of them are fine.. Bad odds if you ask me.. It's not even close to being accurate.. So why bother.. Especially when they just do a U/S anyway to check it.. I just get an U/S at about 20-22 weeks and call it good.. It just seemed silly to me to get a test for something no one in our family has ever had that had a false positive rate that was soooo dang high...

Warm Squishy Feelings..


It's lonely being the only XX in a house of XYs.
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#11 of 14 Old 02-05-2003, 11:48 AM
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My results on the AFP screen were "moderately high," and I got the exact same result when I took the test the second time. I went for a level two u/s and did the whole genetic counselling thing. The ultrasound showed that there was nothing abnormal and my son was born in perfect health. However, that few weeks from the initial AFP test to finding out the results from the level two u/s were extremely stressful, knowing about the possibility of our child having spina bifida. That is why I declined the test this time around (I'm 19 weeks). My aunt also experienced a false positive result with the AFP test.
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#12 of 14 Old 02-05-2003, 12:00 PM
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I just wanted to thank everyone for this thread!
I was planning on having the triple screen in a few weeks, but having read this thread, and doing my own research, and knowing that dh and I wouldn't do anything if it did come back badly, we have decided not to have the test done. With the high false positive rate and my inclination to worry A LOT, I know this is the best choice for us.
So, thanks guys!
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#13 of 14 Old 02-05-2003, 12:51 PM
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My 1st pg I did have the AFP. I was called at work on a Friday and told that the results were waaaaay off. The dumb@ss nurse on the phone asked if twins ran in my family. I said "no" and she replied with, "well it's too high for twins anyway and not high enough for triplets, so the baby probably has renal problems or spinabifida. You HAVE to go for an u/s on Monday." That was the worst weekend of my life. I was blue all weekend and couldn't stop obessing on what we would see at the u/s.
When we got there we discovered TWINS! No renal problems no spinabifida, just twins.

I declined with my 2nd pg and will with this one too. We usu. do 1-2 early u/s (looking for heart and other defects that run in my family.)
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#14 of 14 Old 02-05-2003, 06:02 PM
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In my state, the triple screen is now a quadruple screen. It has a notoriously high false positive rate. The doctor that told someone 10% is not giving accurate information. My understanding is that the majority of postives, in fact the high majority (seems like it was 75+%) were in fact false.

I agree with what most people have been saying - if you wouldn't risk having an amnio to double check the bad result on the blood screen (which I wouldn't) but would only worry the rest of your pregnancy (which I would), there is no point in taking the very unreliable test IMO. If you are worried, I would go first with ultrasound but knowing beforehand would only worry and upset me. If there is something wrong, we will find out at the birth and deal with it then. Currently pregnant with #3 and have never had a triple or quadruple screen.

I do believe in testing for group B strep (I know a woman who was not informed of the test and didn't have it and her baby died a couple days after birth from complications - she did carry it) as you can be treated with IV antibiotics during birth and avoid problems.

There are tons of tests that are made to seem necessary and normal and expected of us. Research and make your own decision as to whether or not they are right for you. Yes, dh has a say as it is his baby too but it is your body. Is he informed of the effects emotionally to you if the test comes back poorly? And what tests that will lead to? My dh originally wanted all medical stuff offered but came around when he learned more. They just want what is best/safest for us - but sometimes they don't understand at first what that really is. Blindly following the medical profession is a mistake IMO...
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