Schizophrenia.com

Blood Test Helps Diagnosis of Schizophrenia


#1

Investigators used serum samples from 10 clinical research study participants who had been diagnosed with schizophrenia, and a healthy control group. Using the new testing method, the research group was able to correctly differentiate the samples of those who had been diagnosed with schizophrenia from those who had no history of the disorder.


#2

Well, I’m glad. People are always lying about me and calling me a fake.


#3

People just have a hard time imagining what psychosis is like. It’s much easier for them to attempt to deny its existence than it is for them to accept its bizarreness.


#4

Seems like doctors trying to debunk mental illness to me, no blood test can diagnose a mental illness


#5

That’d be great if they came up with a blood test for sz. Then people would finally be able to see if they’re really sz. There is no denying a blood test.


#6

Good to see you back @Tyme


#7

The problem with all these tests is that schizophrenia has a base rate of less than 1%. That means a test that is 99% accurate on equally sized samples of sz and non-sz people will be significantly less than 50% correct in the real world. Essentially useless. The test will have to be extremely accurate on equally sized samples to be useful for diagnostic purposes.


#8

The problem is that’s wrong. It would be 99% accurate. If 100 people with sz are tested 1 wouldn’t show up. According to your logic all tests that are 99% accurate would only be 50% accurate.


#9

You seem upset about something? Let me show you how this works.

You can describe test accuracy with sensitivity, specificity, positive predictive value and negative predictive value. Sensitivity is the proportion of the actually sick people who are classified as sick. Specificity is the proportion of the actually healthy people who are classified as healthy. Normally, when we speak of test accuracy, we mean sensitivity and specificity, and we test roughly equally sized groups of sick and healthy people. When these two groups are equally large, sensitivity and specificity will directly describe how accurate the test is with both groups. The positive and negative predictive value, that is, how well a positive and negative test result predicts whether a person is sick or healthy, respectively, will also be .99 in these samples.

Schizophrenia has a base rate of less than 1%. If a test is 99% accurate on a research sample (which means it has a sensitivity and specificity of .99) but there are 99 times as many people in the healthy group as there are in the sick group, 99% of the sick people and 99% of the healthy people will, of course, still be correctly classified. But for every group of 100 people, there will be, on average, 1 sick person and 99 healthy people. That 1 sick person will be classified correctly 0.99 times on average, and those 99 healthy people will be classified correctly 99*0.99=98.01 times. That means, for every group of 100 randomly selected people, there will be 1.98 positive test results, out of which 0.99 (99-98.01) will be healthy, and 0.99 will be sick. So the actual accuracy in the real world, when you consider the low base rate of 1%, will be 50% for a test that has an accuracy of 99% in equally sized research samples. If the research samples are not equally sized, test accuracy is still described with sensitivity and specificity, and the conclusion will be the same. Since schizophrenia has an actual prevalence that is lower than 1%, real-world test accuracy (or positive predictive value in real-world samples) will be less than 50%.

If my oversimplified use of the word accuracy threw you off, I’m sorry. I thought it would be unnecessarily confusing to get into the details of this.


#10

I’m not reading that. There are diseases that affect .5 or less that have a 99% accuracy rate. I think you’re confused. It’s definitely possible to have 99% accuracy rate with a disease that affects less than 1%. I don’t doubt your statistics. It’s just your overall theory that it’s impossible. The problem is you’ll never accept that because you think you’re smarter than everybody. You’re not even the smartest on this forum.


#11

Whatever, Thyme. You could just read it and see what I was trying to point out. People tend to get very excited about results like these, but they’re not as exciting as they seem. That’s why I posted it, and that’s why I took the time to explain it thoroughly. Apparently you weren’t interested in that, you just wanted to tell me off because you don’t like me. Well congratulations on being a dickhead.


#12

I like you and you have me interested. How can a disease that affects .5 or less have 99% accuracy on a test?


#13

Nice bait, but that’s not even what we’re talking about.


#14

Then why did you post that garbage on this thread.Were you just trying to prove your intelligence because you’re insecure about it or just to dampen spirits?


#15

Just to clarify. So you are saying that out of a sample of 100 about 2 people would test positive. One being sz and one not. Is that where you are getting the 50%?


#16

Yes, that’s what I’m saying. This is because test accuracy is normally defined as sensitivity and specificity, and those numbers do not take base rates into account. There have been many studies on tests based on biomarkers, like this study, and they all have very good accuracy on paper, but not nearly good enough to compensate for the very low base rate of schizophrenia.

A test that has a 50% chance of misdiagnosis is not really useful, and most studies I’ve seen do not even approach 99% sensitivity and specificity.


#17

@Treebeard and @tyme, let’s agree to disagree kindly. I don’t think treebeard is showing off intelligence, but rather has knowledge to share. There’s no reason for name calling or cutting each other down just because you disagree. Let’s keep this a support forum. I once got really upset on this forum too and I feel bad about lashing out. So I’m guilty too, no judgment here. I just want to encourage everyone to be kind to each other.


#18

It seems I have an inferiority complex pertaining to @Treebeard I was also a little upset that he was so quickly to dismiss positive research. It’s not often we get that kind of news related to sz. If I remember right Treebeard isn’t even sz. He wouldn’t understand the emotional roller coaster this thread was. One second it was positive news and the second it was bad news. Overall, sorry about the harsh language and perceived tone @Treebeard


#19

I have heard of the inflammation and oxidative stress theory before.
I have been taking nac for many months to try to help combat this.


#20

Here is another article targeting inflammation.
In this one they look at elevated levels of cytokines.