Friday, July 3, 2009

Pondering

I am in a very weird space--I know that the results of the screening test are not great, but I am trying not to stress about it. After all, it's just a screening test. Plus, the nuchal fold measurement was actually fine--it's the blood tests that came back wonky. The blood tests, by themselves, are only 60% accurate at predicting Downs.

I have been having a hard time reconciling the "85% (or so) accurancy" of the NT scan plus bloodwork with the 1/160 chance the genetic counselor gave us. I was trying to figure out if that meant that our chance of this child having Downs was 85%, and if so, where that left us in terms of the 1/160 number (because in that case, shouldn't the number be 85/100?). What the counselor told us is that the "85%" stat refers to the fact that if 100 cases of Downs were considered, the NT scan plus bloodwork would flag 85 of them as being at risk for Downs, and would fail to identify the other 15 as being at risk for Downs. So, the test essentially flags 85% of the cases that it should flag that are actually Downs. However, it also flags a lot of other cases that WON'T be Downs, which is why my stat is still 1/160, and not 85/100. She said that her hospital screens anyone with a risk of 1/260 or greater as "positive" for being at risk for Downs.

I am still a little confused about that 85% stat, because the three pregnancy books I have seem to have a different definition of what that stat means than what the genetic counselor gave me. Frankly, I prefer her definition. The books all seem to suggest that tests are 85% (or so) accurate at actually indicating a baby that has Downs. I hope I'm wrong. If you have a link or a book that clarifies, please send it along to me. You know I am an information whore, even if it's not positive information.

We weren't able to get scheduled for the CVS on Wednesday, as we'd originally hoped. They were completely booked already. I was disappointed about that, because if we'd been able to get in for Wednesday, we would have had results by Friday, which would mean just one more week of not knowing. Instead, we are scheduled for Friday morning (7/10), and will likely get results on Monday. The head of the department at a major hospital in Boston will be doing my CVS, which puts me somewhat at ease. I think the genetic counselor was a little taken aback by how adamant I was that I would only consider having a very experienced doctor perform the test, but whatever. Every study I have read about CVS has found that this is one test where experience matters enormously, and the risk of miscarriage from the procedure is significantly lower with a more experienced practictioner. I generally find that medical professionals are surprised by patients who have actually read the studies, and act as their own advocates.

We decided to hold off on telling our families until we are through this next bit. I definitely could not deal with the dichotomy of congratulations and CVS stress all in one week. I called my mom and asked her to just hold on to the package when it arrives. She was puzzled, but agreed not to open it. I also called my friends who were dropping off the package to my dad, and asked them not to give it to him. They promised that they wouldn't. T. also called his mother (who is eagerly awaiting a big announcement) and told her that there would be no big annoucement this weekend, and that she shouldn't bring it up.

Last night, we were able to stay completely distracted by having dinner with friends, one of whom I hadn't seen in a long time. It was really fun, and I got to catch up on tons of gossip, which is always nice. Today, we are heading into Boston for the day, and catching the Red Sox game--if it stops raining, that is! It has been raining for so long here in New England that I am starting to mildew. Tomorrow, we are headed to the lake for a massive 4th bash with friends and family. That's gets me through until Monday, at least.

UPDATED: I just found this on a medical center website that explains prenatal testing. It is going to carry me through the next few days, I think: Five out of every 100 women who take the test receive a positive result and are considered "screen positive." Most women with screen positive results will not have a baby with Down syndrome.

11 comments:

Heather said...

Hang in there. I will tell you that when I was pregnant with Phoebe, my MSAFP blood test was off the charts. This is part of the triple screen, now the quad screen test. This was past the time for CVS, so we went right to amnio and everything was fine.

You'll be in my thoughts.

~Jess said...

Why can't things ever be easy: We're praying for you guys.

Io said...

I feel like I am back in AP statistics or something, but I have a head cold and it doesn't make any sense whatsoever. Regardless, I hope everyone holds off on opening the package and that you get good news soon so they can find out and not think you re a strange gift giver.

Serendipity said...

I never could understand the stats, just trying to wrap my head around it gives me a slight headache.

I really hope everything goes well on Friday, I'm glad that you have such a senior doctor to perform the CVS for you.

sassy said...

So confusing!! I hope you are able to find some peace in the middle of all of it...

Good Egg Hunting said...

I'm so sorry you have to deal with this but FWIW, I know two people who had wonky tests and have perfect babies. I really wish they would come up with a more accurate test so people wouldn't have to go through this kind of stress. Hoping your CVS is reassuring.

Lollipop Goldstein said...

The statistics confuse me too, but I do know far more people who got a false positive than have gotten a true positive. I'm just holding you in my heart and secretly hoping for a cancellation this week so your appointment gets moved up to Wednesday and you get the results sooner.

JamieD said...

I barely have a good enough grasp on statistics to understand them myself, so I will do my best to explain what I can.

Your BABY'S risk of being born with Down syndrome is 1 in a 160 chance which as a percentage comes out to 0.00625%. NT scans/bloodwork OVERALL have a 85% chance of identifying a baby with Down's. You have it exactly right - out of 100 babies with Down's, the screening will flag 85 of them.

Basically the 85% only refers to the success rate of the testing itself and nothing specific to you.

I hope this eases your mind a bit while you are waiting on your CVS results. I'll be thinking about you.

Anonymous said...

The test results mean that if you had 160 pregnancies with exactly those numbers as were measured in your case, (only) 1 of them would be a pregnancy with a baby with Down syndrome.
The other number (the 85%) is a general number that is the same for everybody. It means that for 100 women actually carrying a baby with Down syndrome the test will accurately identify for 85 of them that the baby is having Down syndrome.
Something on the side, the NT number is "more important" than the blood tests in this regard, that it also shows lots of more potential problems (congenital heart disease, increased risks for something going wrong later in the pregnancy etc). A low NT number is a very good thing. And the bloodwork is less trustworthy for women that are either uncommonly heavy or uncommonly light, even if the software usually corrects the numbers for weight. Trust in your NT results!
I wish you all the best for the upcoming CVS!!!

Gabby said...

i so hope you are just like most women.. you are right? you wear makeup, you do your hair, you wear skirts sometimes, you talk on the phone.. you, like most women who have a positive on their screen.. will not have a baby with Down's..

btw, my sister had a screen positive with her 6 year old. she has a healthy beautiful 6 year old girl. I hope you do, too in 6 years and 7ish months.

B MoM said...

I had a "positive" test for downs on my Quad test. I got TONS of helpful information from babycenter.com on the amniocentesis group board. Go there for more info. Your chances are great. My chances were 1 in 77 for a baby with downs. We had a level 2 u/s down two weeks ago after we received the quad results. There were no markers for downs, so we opted not to do the amnio given the risks for MC. We go back again in 2 weeks for one more level two u/s, so that the perinatologist can do a more thorough exam on our baby's heart. I'm thoroughly convinced that our baby does not have downs, and I just ended up having blood levels that put me in the "risk" category. That happens a lot. good luck to you.

LFCA