[arcticbull]

Don’t make me tap the sign.

Bayes Theorem: https://en.wikipedia.org/wiki/Bayes'_theorem

There’s a very good reason we don’t test asymptomatic people in low incidence populations. Basically all positives are false positives when you do that, no matter how accurate the test is.

When you’re testing healthy randos for everything the odds of a positive being false have so many 9s it would make an SRE weep.

Unless this is accurate to a degree previously unheard of in medical science it’s a boondoggle, and I can’t help but notice there’s no mention of accuracy.

Unfortunately that’s just basic statistics.

[appplication]

So you are certainly correct but you can also tighten up your definitions for true positives as you have more information on your false positives. There may exist additional signal as well.

To your point though I think there is a difference between collecting and evaluating additional data sources and using them as diagnostic tools.

I suppose I fundamentally disagree with the implication of your post that there is no value in gathering further data for these reasons, it would seem to suggest we’re already diagnostically optimal and could not do better with additional signal.

[arcticbull]

Sure collecting more data makes sense. We agree there. If that gets you to the required degree of statistical confidence my argument is moot.

[jibal]

Positive for what, exactly? Quoting convnet, above:

> The downside, and the reason why most doctors do not recommend full body scans, is that every human body is a bit weird and there will almost always be something "wrong" that will be visible in a full body scan. This can lead to unnecessary testing, anxiety, and even unnecessary procedures. Many of these oddities flagged by the scan would never have caused any actual issues had the patient never been aware.

The fundamental problem is that you generally can't diagnose simply from shapes. Scans show shapes, shapes cause concern, concern leads to invasive procedures, results are negative.

Also, overdependency on "spas" for health information could lead to an atrophy of other sorts of medical information gathering and diagnosis. e.g., there's no mention in the dreamy description of this spa experience of getting a blood draw or a patellar reflex test.

[hereme888]

That's precisely where medicine is headed: personalized medicine.

You [hopefully] won't have to become a rare missed diagnosis because you didn't fit the demographic for this or that screening test.

Cost of genomic analysis is exponentially decreasing, and so much progress is happening so quickly.

Consider for example how in cardiology we advanced from ASCVD's 10-yr prognosis, to the PREVENT 30-yr prognosis. And still most providers are using the ASCVD score for their patients.

[arcticbull]

You’re dealing with populations here. Literally the odds of a positive being false would be over 90%. Much higher in the more rare conditions. I’m not exaggerating. That means every almost every follow up you do is a waste of time, money and limited resources, denying care to those who need it. Including you when you actually do need it. It also exposes you to the risks of unnecessary follow-ups like infection. Your expected outcome is worse this way.

The chance a positive is real is so low you may as well just point to a body part and get it biopsied.

A positive from this kind of test is statistically meaningless.

[munificent]

It's scary in both directions.

If you let it give out tons of false positives, then patients are trained to ignore it when it cries wolf.

If you dial it back so that it gives out fewer positives, then now it starts giving out false negatives and not helping sick people.

[krzat]

If this argument was as solid as you say, then all routine checks would be pointless.

I don't know about traditional blood testing, but a permanent implant which checks HR, pressure, glucose, temperature & oxidation would be pretty useful, not necessarily to diagnose anything, but to provide data for doctor when patient has actual symptomps.

[ricardobayes]

They kind of are. Spain doesn't have yearly physicals, and during a GP visit, they don't even take your blood pressure. Blood tests are extremely uncommon, unlike in British medicine, where they take your blood pressure every time and blood tests are so prevalent people usually request one from time to time despite having no symptoms. Spain's example showed the above (or the lack of) doesn't increase all-cause mortality and even excelling in longevity statistics.

https://www.rieti.go.jp/en/columns/a01_0455.html This japanese article found "No clear-cut evidence exists to determine whether undergoing health checks leads to greater longevity and/or lower medical expenditures."

[arcticbull]

Several published papers agree. There is in fact little evidence to support regular checkups if you’re asymptomatic.

https://pubmed.ncbi.nlm.nih.gov/31642821/

And blood pressure is especially pernicious, basically every doctors office measures it wrong so the results aren’t particularly useful. Many use the wrong size cuff for example, or don’t give people time to relax before a reading. A ton of people have white coat hypertension, high BP only because they’re in a doctors office.

https://pmc.ncbi.nlm.nih.gov/articles/PMC1120072/

I saw a paper that showed only 36% of cardiologists did it right.

[jibal]

Math does indeed make for solid arguments. If you want to make a counterargument then you have to address their math, which you didn't.

[ricardobayes]

Medicine is not a statistical field. I've seen many times doctors dismissing someone "you're young, you can't have X". Although there is some truth in what you're saying: full body CT scans are on the rise now.

[gfodor]

You can just run more tests to get increased statistical power.

[cbolton]

No you can't. Statistical tests assume independent data points. Testing the same individual repeatedly would be pseudoreplication, leading to wrong conclusions.

If you mean run different tests, where you collect different kinds of data from the same individual, sure but that's not something you can "just do" in the general case.

[moralestapia]

Many smaht people have already pointed that out.

It's news to no one that tests are imperfect.

Do you have any concrete solution to that? Anything of value?

[arcticbull]

Yes, don’t do tests on asymptomatic low-risk people until you can demonstrate that a positive result has any meaning whatsoever.

[aipatselarom]

Hypertension is asymptomatic for years and is prevalent in every demographic. Leaving it unattended it can cause stroke, heart attack, or organ damage through long-term vessel strain, by which time damage may be irreversible; detecting it on time can prevent this with lifestyle changes and medication.

Diabetes is asymptomatic for years and is prevalent in every demographic. Leaving it unattended it can cause damage to blood vessels, nerves, kidneys, and eyes through chronic high blood sugar, by which time complications may be advanced; detecting it on time can prevent or delay this with treatment and lifestyle changes.

Hyperlipidemia is asymptomatic for years and is prevalent in every demographic. Leaving it unattended it can cause artery blockage through cholesterol buildup, by which time heart attack or stroke may occur; detecting it on time can prevent this with diet and medication.

Kidney disease is asymptomatic for years and is prevalent in every demographic. Leaving it unattended it can cause kidney failure through gradual loss of function, by which time dialysis may be needed; detecting it on time can slow progression.

Glaucoma is asymptomatic for years and is prevalent in every demographic. Leaving it unattended it can cause irreversible vision loss through optic nerve damage, by which time blindness may be permanent; detecting it on time can preserve vision.

--------

I'm SO glad you're not my family doctor!

[arcticbull]

At least the top 4, unclear about the 5th, are strongly associated with obesity. That would make someone high-risk and testing potentially warranted in like 70% of the population. Asymptomatic and low-risk is what I said. The incidence of hypertension is so high in the general population it’s almost always statistically supported (even though basically every doctors office takes it wrong, even cardiologists, amazingly).

On the other end of the spectrum, what doesn’t make sense is testing a random person off the street for Ebola. The prevalence approaches zero and symptoms are fairly noticeable, so any positive test is definitely wrong.

Most diseases are in between and have to be evaluated case by case, not buckshot.

You may be particularly interested to hear that there’s little evidence to support regular checkups in most adults beyond blood pressure testing and cervical cytology.

> Given the lack of favorable evidence and the potential adverse effect, primary care providers should consider the fact that general health checks, beyond the screening interventions shown to have benefit, likely have little or no effect on important health outcomes. Some of the interventions with demonstrated benefit have sufficiently large effects that a uniform application is warranted (blood pressure measurement and cervical cytology screening). In others, the trade‑off between benefits and harms is so close that patients should be involved in fully shared decision making regarding their participation (breast and colon cancer screening).

https://pubmed.ncbi.nlm.nih.gov/31642821/

I suspect your doctor would agree with me. See if they’ll test you for Ebola, for instance. Not because you have symptoms but just cuz.