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Blood test that finds 50 types of cancer is accurate enough to be rolled out

theguardian.com

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Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#151

> It correctly identified when cancer was present in 51.5% of cases, across all stages of the disease, and wrongly detected cancer in only 0.5% of cases. While I think this is a great step forward, How can this be described as highly accurate when it missed identifying cancer in 48.5% of the people?

And is only 18% accurate when looking at stage 1 cancers.

https://www.theguardian.com/science/2020/mar/31/new-blood-te...

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#152

Earlier quoted context omitted.

Who are "we"? I'm certainly not "regularly" screened.

That's your choice, assuming you live in a developed country. Assuming the United States see here: https://www.cdc.gov/cancer/dcpc/prevention/screening.htm and if elsewhere consult your local CDC equivalent.

Current screening methods tend to be costly and/or uncomfortable for the person being screened. A simple blood test could lead to higher uptake and more regular screening.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#153

Earlier quoted context omitted.

Actually you don't want this, and you are describing a nightmare scenario that everyone who studies health policy understands all too well. Mass screening of healthy people will result in extreme iatrogenics and unnecessary psychological damage and stress (which leads to physical effects as well), not to mention overwhelming the medical system. The fact is that many things that could be detected will never result in…

Utterly wrong. You are conflating current technology like MRIs and CT scans that only detect lumps, to blood tests that detect CANCER. Yes, if every lump were treated and excised then it would be problematic. But CANCER is different. The only cancer that you might be able to leave alone is prostate because it grows so slowly. Everything else is a risk. And if we can treat cancer at early stage 1, then maybe people wo…

cells turn cancerous all the time and usually the body eliminates them without issue. this blood test is still going to hit all sorts of "false" positives, where it detects some cell that has gone cancerous that would have been eliminated anyway.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#154
post #146

This is one of those medical revolutions that I am waiting dearly for. Facilities that are not hospitals(to avoid the risk of occupying medical devices that sick people need) built to _regulary_ check up otherwise healthy people for preventive care. Heck, I have so many alerts defined on my monitoring setup for servers to watch for signals of failure before they get too big. But, my own body is not observed until som…

The reason this is not happening isn't a technical one. It's that people with a medical background will tell you this isn't a healthy utopia, it's a nightmare. Medical tests are complicated. They often have significant false positive and false negative rates. Testing people at scale increases the number of people with wrong test results and can cause harm if you start treating people based on wrong test results. The…

The point of this is not that you get a definitive diagnosis; it's just a somewhat reliable marker on whether you may need to be concerned and get more accurate (but more harmful) imaging or invasive tests to rule out something.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#155

This is one of those medical revolutions that I am waiting dearly for. Facilities that are not hospitals(to avoid the risk of occupying medical devices that sick people need) built to _regulary_ check up otherwise healthy people for preventive care. Heck, I have so many alerts defined on my monitoring setup for servers to watch for signals of failure before they get too big. But, my own body is not observed until som…

Actually you don't want this, and you are describing a nightmare scenario that everyone who studies health policy understands all too well. Mass screening of healthy people will result in extreme iatrogenics and unnecessary psychological damage and stress (which leads to physical effects as well), not to mention overwhelming the medical system. The fact is that many things that could be detected will never result in…

Mass screening of healthy people will result in ...

But you don't know they're healthy. They might be sick but (so far) asymptomatic. That's why you screen, if you have a sufficiently accurate test available and you can make a useful intervention if the test gives a positive result.

If we applied your argument consistently, we would abolish all cancer screening programmes, resulting in many extra deaths because early detection and treatment didn't happen. We'd stop checking up on heart health as people age, resulting in many extra deaths because people continued to live unhealthy lifestyles without realising what it was doing to them. We wouldn't be using rapid testing for COVID-19 to detect and isolate probable asymptomatic carriers who might spread the virus to others who wouldn't be so lucky. The list goes on.

Good screening programmes save lives. It's as simple as that.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#156
post #44

Earlier quoted context omitted.

A big part of this is the fact that learning information (about a disease or condition) early is often NOT the same thing as learning information that will change a patient’s clinical outcome.

Yup. Let’s say the test shows “very likely” for pancreatic cancer. Now you do imaging. Ok, nothing there? Now what? Biopsy? That’s general anesthesia now and costly (for the patient or govt). Biopsy is negative. Now what? Start chemo? Watch and wait? For how long? Do a biopsy every 6 months? None of these tests are 100% accurate. If broadly used, a false positive of 0.1% will result in tens of thousands getting unnec…

> Now you do imaging. Ok, nothing there? Now what?

Put the patient on a more frequent screening schedule (blood tests and imaging) to pick up any growth.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#157
post #5

This is one of those medical revolutions that I am waiting dearly for. Facilities that are not hospitals(to avoid the risk of occupying medical devices that sick people need) built to _regulary_ check up otherwise healthy people for preventive care. Heck, I have so many alerts defined on my monitoring setup for servers to watch for signals of failure before they get too big. But, my own body is not observed until som…

That's already a thing, at least everywhere I've ever lived. You have a primary care doctor, you see them at least once a year, they do a physical exam, maybe some blood work. This test maybe becomes standard of care for everyone annually.

I've never lived anywhere where this was common. The public health system can't afford to fund it and most of the population doesn't want to (or can't afford to) pay for it themselves.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#158

This is one of those medical revolutions that I am waiting dearly for. Facilities that are not hospitals(to avoid the risk of occupying medical devices that sick people need) built to _regulary_ check up otherwise healthy people for preventive care. Heck, I have so many alerts defined on my monitoring setup for servers to watch for signals of failure before they get too big. But, my own body is not observed until som…

Regularly checking people that are otherwise healthy for cancer will turn up a lot of cancer through false positives or slowly growing ones, will lead to a lot of unnecessary intervention and will in fact lead to a reduction in quality of life and lifespan. This is one of the reasons why exhaustive cancer screening (which was more costly in the past but could have been done) was not promoted, it had nothing to do wit…

> Regularly checking people that are otherwise healthy for cancer will turn up a lot of cancer through false positives or slowly growing ones, will lead to a lot of unnecessary intervention and will in fact lead to a reduction in quality of life and lifespan

This is completely irrational argument. Catching cancers early is crucial.

Furthermore, if better information leads to unnecessary intervention the blame lands squarely on the hospitals being overzealous and greedy.

> For aggressive cancers - the ones that are really problematic - you would have to do such a test too frequently to make any real difference

Because aggressive cancers go from 0 to dead in a week? Please.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#159
0.5% false positive rate is actually quite high. I don't have the numbers, but I'd be surprised if more than 1% of the people that would receive such a screening actually already have cancer, which would mean that it produces about as many false positives as false negatives.

Picture a population of a million people, all receiving the test. 1% of them have cancer (unknown to them) - half of those people get a negative screening result and half get a positive one (51% successful identification), and 0.5% of the full population get a negative screening result. Those numbers are roughly equal.

That doesn't make it useless by any means, but it's not nearly as 'specific' as it sounds on paper.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#160

Earlier quoted context omitted.

The argument you’re making has always bothered me because it’s hiding the ball. If finding something that otherwise carries no symptoms is best left untreated, then the fact that you found it should make no difference to the decision. The doctor should say that the best course of action is to do nothing. More information can never be harmful. If you know information is best not acted on in the abstract, then you also…

Lots of problematic assumptions in your reply. >If finding something that otherwise carries no symptoms is best left untreated, then the fact that you found it should make no difference to the decision. The doctor should say that the best course of action is to do nothing. More information can never be harmful. Absolutely and demonstratively false. There is an entire field of health policy that destroys this harmful…

>Many times the patient will push them for further tests and treatment (or the doctors will advocate for it to ease the mind of the patient) which leads to potential harm from unnecessary treatments.

>People will ask to be treated anyway, and iatrogenics will rear its ugly head.

I just want to say that you are in agreement with my position here.

Your point about psychological problems is interesting, but as long as people know what they’re signing up for, it’s okay. Some people aren’t prone to anxiety. Why should they pay the price because other people are? Part of my original point was that implicit in your argument is that people capable of handling it should be denied something because more people incapable of handling it can’t be stopped from hurting themselves. I think many people do not agree with that moral reasoning, so medical people hide it behind objective looking statistics.

And as for cost, I don’t take any arguments from medical people about cost seriously. The reason why costs are so high is because doctors and the medical field as a whole run a massive protectionist racket to keep the supply of medical professionals low.

How fresh of them to say that because they’ve limited the supply of medical resources to enrich themselves, patients must pay by having less access to care.

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