Screening vs diagnostic tests

[mummyjah]

Hi all,

I would like to canvass some opinions regarding screening vs. diagnostic tests. The FMC advise you to test at 1 in 300 (or thereabouts). However, that is still 99.65% chance that everything is fine. How do we make a decision based on numbers when anything pretty much either side of that number is only going to change by .2, .4, etc. of a percentage point? Most large hospitals/FMC have low miscarriage rates in diagnostic tests (e.g., one in 1000 +). How do we engage in decision making on the basis of .2% or something similar, and compare that to the miscarriage rates? Do other issues, e.g., life circumstances take over, such as age, health, number of other children? Why not skip straight to diagnostic tests when the 'odds' tests tell you that over 99% of the time, things are ok anyway?

I have always thought pre armed is forewarned, however my sister believes as she would never abort it doesn't matter.

I think any information that means you can ease your childs way into the world and know how best to help it through life is best.

To be honest you have to go with what is right for you x

If everyone had invasive testing, there would be a far, far higher number of babies lost. Yes, many places are as good as 1 in 1000, but plenty of places especially outside of major cities are more like the 1 in 100 we all get quoted. I have heard of too many people losing their babies to amnio/CVS to know it is not that uncommon.

Screening is fantastic in that it can identify (with the combined test) 90-95% of the babies that might have chromosomal issues. I believe only 1 in 20 women screen positive. Many of those don't opt for invasive testing, and similarly some who don't screen positive DO opt for it. Overall though it would mean that probably twenty times as many babies would be lost to invasive testing if we didn't screen first and the vast majority of those would be healthy.

Yes, a few babies with chromosomal issues get through and are born who might have otherwise been terminated but this is not necessarily a bad thing in every case.

The only downside with screening is the extra worry it brings if you do screen positive. But if everyone was going to have to choose invasive testing anyway (or not) then it's not really changed that decision.

In the next few years a non-invasive maternal blood test will become available which detects I believe with 97% accuracy if the baby has Down Syndrome. If the test comes back negative then you can be 100% sure the baby does NOT have Down Syndrome. So you would only have the invasive testing if it was already pretty much a done deal.

Bring it on and spare people from these awful choices over invasive testing.

Like sparklies I say bring on the blood test...

I have screened positive twice (1:80 DS & 1:22 Edwards syndrome). Went on to have CVS and both times I was the '1'.

Both scans at CVS also illustrated further issues and neither baby was ever going to survive pregnancy. With the Edwards syndrome pregnancy I was adamant that if I was high risk for Downs again I was not going to risk miscarriage by having CVS...but when the risk of Edwards was so high I felt that I had no real choice but to have it done.

I am due for screening tests next week and am currently very certain that I will not be having CVS for a DS risk factor, and would prefer to wait til 16 & 20 week scans for more detailed looks. If DS is suspected I would probably have amnio late on to confirm just to be as ready as we could be for a child with special needs (explaining to our other children, medical expectations etc).

If the results give us high risk for one of the fatal trisomies I would then make the decision about CVS or amnio.

In my experience the decision on whether to have diagnostic tests made itself. I was also really supported and guided by the expertise of my consultant..

With my 2 DD's our risks were in the 1:8000 league so never any decisions to be made.

I think ultimately the decisions on screening V diagnostic tests is very personal and unique to each pregnancy and circumstance.

babylily, I am so sorry for your losses, what ridiculously horrible bad luck. I am so glad you were able to find out early on that there were issues.

That is exactly my stance too - no invasive testing for me for Down Syndrome but I would for one of the fatal trisomies. I love that we have the option.

What I forgot to say in my post (I think I was treating the OP's post as should everyone forgo screening rather than should we as individuals) is that yes, of course it is completely up to the individual if they do the screening or not. So much depends on past experiences, knowing your own feelings and much more. I would never judge anyone who turned down screening. And if someone can only go ahead with a pregnancy if they want to be 100% sure then yes - straight to invasive testing is the best bet for them as individuals. But it is not for everyone.

Thanks everyone. The issue that I am getting at here is that the more I think about both types of tests, the less I think of them as 'progressive', from one to the other. One gives you odds, the other gives you certainty. They are completely different, from what I can see. Even with great odds, you can never be fully sure. In addition, great odds are not that different from the recommended testing level (which are also great odds that everything is fine). Why would you test at 1 in a 100 when there's 99% chance that things are fine? Why do the medics define this as high risk, when clearly it's not? I have no idea how to go about making a decision about odds when chances are that all is fine. I'd find it easier (to decide; not to do) re diagnostic tests, which seems clearcut in terms of the decision making process.

I declined second trimester invasive testing for 1 in 34 for T21 (still don't know the outcome as I'm 28 weeks) simply because there's a 97% chance everything is fine and we wouldn't terminate anyway. It would be different for 1 in 5 I think, in terms of "need to know" at least.

Invasive testing is usually offered anywhere between 1 in 200 and 1 in 300 depending on the clinic, which seems excessively high to me as well. The risks of an amnio/CVS - around 1/100 to 1/400 depending on what you read or the clinic are about the same as the cut off.

The argument goes that given most people are expected to terminate for being "the one" (nearly everyone will terminate for a lethal trisomy, and 90% will for Down Syndrome) so when the risks of the invasive testing are LESS than the chances of the baby not having typical chromosomes, then it makes sense to test. In other words, the risks are weighed up against each other. Actually I don't think it makes any sense at all as one does not directly affect the other, but that is the reasoning most places give and people seem to be happy with it.

Hi, I'm new but this is something that has been playing on my mind since we saw our genetic counsellors last week.

I had to say goodbye to my baby girl a month ago at 26 weeks. She had Edwards syndrome. We decided to have an amnio so late on because she had a heart defect and was small for dates and so were advised to have a diagnostic test because her symptoms suggested a chromosomal abnormality. We agreed but I never thought I would test positive.... At 13 weeks I had gone privately for a combined nuchal & bloods, which came back as very low risk. In fact I was given a 1:119000 chance of my baby having Edwards.

We have talked about ttc in the near future and having discussed our screening tests and options which could be given to us in the future (I am 31) I still don't know how I view these tests and the statistical gamble that comes with CVS and amniocentesis. They have given me, as seems to be usual, a 1 in 100 chance of future babies having chromosomal abnormalities, of which over half would expect to be Edwards. 1:100 is a hell of a difference from 1:119000 but at what figure can you be 'safe'?

I am so very sorry to hear about your baby girl :-(

You can't ever be "safe" unfortunately.. in fact even invasive testing has a tiny margin of error, related to human error usually, but it's generally thought of as about as reliable as you can get and the only way you can know for sure. There will be a maternal blood test soon (i.e. not invasive) but it will only detect Down Syndrome and will not be available for at least a few years yet.

The issue with the combined first trimester screening is that it has a 95% detection rate - i.e. 5% of babies with chromosomal abnormalities will NOT screen positive - e.g. under the 1 in 250 cut off. Your little girl just happened to fall into that 5% unfortunately.

It's quite common for babies who are positive for various trisomies to have performed really well at the combined screening. If you take a look at this article:

herkules.oulu.fi/isbn9514270290/html/c829.html#AEN831

you can see that the small handful of babies in the sample (of several hundred) who were diagnosed with Down Syndrome, a couple of them had really good odds in the thousands. I imagine it came as a huge surprise to them as it did to you.

No matter what your bloodwork, you will always "screen positive" now at NT because your odds can never be lower than 1 in 100. As to whether you do the amnio or not is up to you and a very personal decision. I did not do the amnio for Down Syndrome but that is because it is not a lethal trisomy so in our case we wouldn't terminate.. it would be very different for T13 or T18.

I am really sorry you are going through this.

Thank you Sparklies for your kind words and for taking the time to respond. Things are all still very new and following a very informative meeting with genetic counsellors I'm trying to make sense of the statistics. This is mainly for the future as I am not angry or blaming the hospitals for not picking up on her condition sooner. In fact I feel lucky that we had her with us for as long as we did and I don't believe this pain would have been any easier if I'd been told 10+ weeks earlier.

When I took the screening tests I understood their limitations but I think it's natural to feel like you've passed a hurdle when you get such very low risk results (1 : 119000). This combined with no other pregnancy problems in the past, my age (31) and the fact all ultrasounds came back fine until 23 weeks... It was basically a huge shock. Medical opinions seem to agree with me.

These are obviously very personal opinions and
decisions and this process has taught me that these often change when you are put in such a
position. We decided on the amnio mainly because the
last dr to scan me saw that Ava had overlapping
fingers one one hand- an indicator of Edwards.
Combined with her heart problems I feel that we really
did not have any choice in testing and ultimately the
termination of the pregnancy- even though a part of
me I wished I could have had her a little bit longer.

Thank you for the link- it makes interesting reading. I
have also read (since our diagnosis) that the blood &
NT screening tests only pick up 60% of Edwards
babies. Again, statistics are starting to baffle me.

Because the risks are now the same as invasive testing I think it's an almost impossible decision. I am a long way off having to make this as I only delivered Ava a month ago, but my follow up appts have made me think and I would like to have an opinion before I conceive.

Sparklies, I see from another thread that you are in the middle of what must be an agonising wait and the possibility of a late amnio. I just wanted to say that I will be thinking of you and I really hope that whatever you choose (amnio-wise) that you have a healthy baby to take home.

Yes, you were extremely unlucky - somebody has to be that 1 in a few hundred thousand but you never expect it to be you, with good reason. I've spent a lot of time on boards related to these subjects over the last 3 months and it is safe to say I've never heard of a case like yours. Most of the time with the trisomies other than T21 there are markers visible on ultrasound long before 23 weeks or bad bloodwork at the very least. I just can't imagine getting that news so late, it isn't fair.

I always swore I would never ever have invasive testing, but when my results came back screen positive I was genuinely surprised that I seriously considered it (even almost booked the appointment) for quite a few weeks before ultimately deciding not to. You are right, until you are in the situation, you really cannot know how you will react.

When babies have T21, the risks are 1 in 100 but mostly for T21, so depending on how the parents feel about termination it can be easier to decline an amnio. But with a lethal trisomy it's very different. I guess on the plus side, such as it is(!), knowing you will screen positive regardless, you have a lot of time to mull it over at least - most people only have a few days before the CVS cut off.

It is one of the hardest decisions a parent has to make - whether or not to go ahead with invasive testing. For some it is clear what to do (really low or really high odds) but for those of us in a grey area, it is agonising. The only advice I can give is to consider all the options and how you would feel if each eventuality came to pass. For me, the thing that tipped the balance was knowing I couldn't live with myself if I lost my baby to amnio when I wouldn't be terminating. Others are more pragmatic about such things and are able to see it more clearly as an acceptable risk and would never regret it no matter what - we are all different.

Thank you for your kind words too. The wait has not been easy and I often have pangs of jealousy for people who have successful invasive testing early on and typical chromosomes reported so they can enjoy their pregnancy. I have to keep reminding myself why I made my decision!

As you say, you have a 97% chance that your baby does not have T21... I suppose you have to stay positive but be prepared. You are a very strong woman.

The geneticists' opinion on invasive testing was that you have to weigh up what would be worse to you- losing a healthy baby due to the test or having a baby born with the condition.

That is obviously different in every situation and every family.

As I say, the more I think about it I don't believe it would have been any easier to find out at 15 weeks than at 23 weeks and if it's likely that they would pick up another T18 baby through ultrasounds initially from 20 weeks then I don't think I could risk losing a healthy baby. However it would have been horrendous to wait for her to die and worry that she was in pain for her short life. I'm sure my opinion will change a few times though!! I have no idea how I'd deal with T21 and I think my opinion has changed since I had Ava.

So sorry to hear of what you are going through, MyAngelAva. I agree with Sparklies in that I have never heard of a case such as yours. I really hope that things ease with time.

Thank you mummyjah. The more I read, the more I realise how unique our story is... To have a small nuchal measurement, good bloods etc. To be truthful I'm pleased that Ava had overlapping fingers on one hand when she was born because sometimes my mind plays tricks and I wonder if they got the diagnosis right (I had an amnio but my 1st reaction was that they mixed up her sample... Crazy I know!)

Not crazy at all.. I think I would always wonder until I could see it for myself and I am so glad you had that opportunity. No test is 100% accurate because of the factor of human error after all!

I don't feel particularly strong right now, I have to say.. I knew waiting it out would be hard but it really does bring you down in all aspects and in my case at least, it can border on the obsessional. Having said that, the worst case scenario from the alternative would be a million times worse for me. It is such a personal decision to make.

Yes, losing a baby in the second trimester is horrific no matter when it happens - you're already completely attached. I am quite certain I would be no less sad at 15 weeks than 23 weeks either.

Wishing you lots of luck with your future decisions - I don't envy you them one bit :(

Thank you Sparklies and I really do feel for you. Remind me again how many weeks you are? I can imagine the wait is torture... It was bad enough waiting over Xmas and hoping Ava would grow, which was only 2 weeks. She was just over 26 weeks when she was born.

It is an incredibly brave thing to wait it out and I admire you. I have to say I have no idea what I think I would do... as I say I don't think you ever really know until you're there. I never thought I'd have an amnio. I assume that it's your screening test alone that is causing the concern- no markers or any heart problems etc.

I have to say that I was a woman posessed waiting the 3 days for the amnio result- I was on the Internet frantically looking for clues and second guessing....

Yep, the two week wait when trying to conceive has nothing on the waits involved in finding out if there is a problem with your baby, that's for sure. It's so much more intense because there is already a baby you have bonded with. I have to admit part of the reason I didn't do invasive testing was the thought of that 3 day wait.. ugh.

I'm 29 weeks so I've known there might be an issue for 17 weeks now. It was all in the bloodwork - I've had totally clear scans, nasal bones, heart, the lot and normal NT measurements on top. Even baby boy's femurs are measuring 2.5 weeks ahead (he's 1.5 weeks ahead in general) and babies with Down Syndrome often have short femurs. My two DDs had short femurs and one of them had a couple of very soft markers (i.e. borderline measurements) as well - so glad I haven't had those with this pregnancy! I even have an "explanation" for my higher bHCG at my 12 week bloodwork - in early pregnancy with all my pregnancies I have crazy high bHCG so I think it's normal for me. Similarly the low PAPP-A - apparently low placentas, like mine is, often have lower PAPP-A too.

So the likelihood is that all is fine, but as you know only too well it is always possible to be "the one". I have been on the surprising end of statistics in previous pregnancies (not for chromosome stuff) so it is hard to always think positive.

I think with a longer wait it is a lot easier day to day than the intensity of a wait where you know the results will be due shortly. Having said that, I have not yet reached the last few days before finding out so I imagine things will get pretty bad around then!

In your case I would most definitely have got an amnio, but every situation is so, so different. With higher odds for Down Syndrome, I'd have got an amnio too, but with less than 1 in 100 I'd not even really be worrying about it now. If the odds had been 1 in 34 for a lethal trisomy I'd have possibly got it done as well. I just happened to unfortunately land in a very grey area for my own personal beliefs and feelings and it sounds like your next pregnancy will be similar for you.

Oh, for a time machine or at least a non-invasive early first trimester test with a full karyotype!

That is all so positive and I'll be thinking of you. From what I understand from our discussions re Ava before she was diagnosed (they suspected she may have had DS) the growth seems to be quite a major factor. The geneticists told me of that test, they said the next couple of years I think. Fingers crossed!

Thank you! It does all look positive and most days I think it will be fine, but there are always days where I am sure I am "the one" despite everything.

Yes, I have heard growth is a major factor too.. although weirdly this little boy is not measuring as far ahead as his sisters were at this stage! Then again every baby is different.

I know they will have a non-invasive test for Down syndrome in the next couple of years, but they haven't yet come up with anything as reliable for the other trisomies. I am sure they will in time though, and I can just see in 20 years time people will look back in horror at the awful choices we had to make in the same way we wince at x-rays (instead of ultrasound!) in pregnancy now!

Bump x