The problem with medical tests.

Here's why you shouldn't put much stock into medical tests.

Example 1:

Let's say that you are an average couple and you want find out if your child-to-be will have Down syndrome. The doctor tells you that there is a test with 95% accuracy. You take the test, and it's positive for Down syndrome. Now, how worried should you be?

To begin with, the chances were approximately 1 and 500 that your child has Down syndrome. This means that out of every 1000 people born, 2 will have Down syndrome.

Now let's give these thousand people the test mentioned above, which is 95% accurate. It turns out that 50 will be tested positive for Down syndrome. But we've just seen that only 2 actually have Down syndrome. This means that they're still only a one out of 25 chance that your child has Down syndrome, which is only 4%.

In other words, if you are a typical pregnant couple, and you take a medical test for Down syndrome which is 95% accurate, and you test positive for Down syndrome, there is a 96% chance your kid does NOT have Down syndrome. Does that make sense?

Example 2:

Let's say that you already have a child with Down syndrome, and therefore the chance is 1 in 100 that your next child will have Down syndrome. You take the test mentioned above and it comes out positive.

(This means that for every 100 people tested, there will be five false positives, and one true positive. This means your chances of having a child with Down syndrome would be one out of five, or 20%.)

In other words, if you are a couple in a high-risk category, and you take a test for Down syndrome which is 95% accurate, and it comes out positive, there is an 80% chance your child will NOT have Down syndrome.

Now how valuable do these medical tests sound?

Our 12 week ultrasound.

On November 18, Cindy and I went for a 12 week ultrasound where they would do a bunch of preliminary tests to see if the baby has down syndrome.

First, they checked his face. The doctor said there was a "nose bone", which apparently is a good sign the baby is healthy. Apparently babies with down syndrome often don't have a nose bone.

Then he checked blood flow for a vein leading to the heart. Normal flow. Another good sign. Babies with down syndrome often have holes in their heart (as we know only too well...).

Then he checked growth. Normal size. Good.

Then he checked fluid behind the neck. Normal amount of fluid. Babies with down syndrome seem to have lots of fluid back there.

All these are good signs and we were pleased. He gave Cindy some blood tests and then a batch for some more and then, apparently, when they analyze the results they will let us know with 95% certainty whether the baby has down syndrome.

Meanwhile, it was a fun day. I could see the baby clearly. At one point it waved it's hand at me when I was talking to it. It fell asleep and wasn't moving and we were all waiting for it. The doctor came over and started jiggling the womb, trying to wake it up so he could see better.

Good times.

My son can read. He’s two years old and has Down syndrome.

On Jake’s two year birthday we were showing him some reading cue cards and I showed him the word “Hi”. He waved. I showed him a bunch of other words, then back to hi. He waved again.

Then I showed him the word “clap”. And he clapped. Today, I showed him the word “nose” and he touched his nose.

He’s two and has Down syndrome. We’ve been signing to him since he was about 6 months old. He stared signing back when he was around a year old. Now he knows more than 80 signs.

We just started the reading thing a few days ago. He loves it. Gets very excited. His default answer to most of the cue cards is “Mom, mom, mom.”

When he reads “clap”, we praise him and clap. He gets excited and starts clapping for the next few cue cards. Very cute.

It’s hard to describe how amazing it is to see your son learn. Especially when your son has challenges and obstacles most people never have to face.