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Toshiba device tests cancer types from a drop of blood

japantimes.co.jp

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Re: Toshiba device tests cancer types from a drop of blood

#41

Post by [deleted] »

_Microft wrote: post #19
BiteCode_dev wrote: post #14

Earlier quoted context omitted.

If it's very cheap, fast and convenient, then it's enough for at least screen the population regularly. Catching only part of the cancers is quite nice already.

No, not necessarily. Check out these numbers: Sensitivity is what fraction of the affected people are actually found. Here: 90%, so 10% are missed. Specificity is what fraction of the unaffected people are detected as such. Here: 95%, so 5% wrongly detected ("false positives"). In Europe, there are 60 cases of lung cancer per 100 000 people. That makes 54 correctly detected per 100 000, missing 6 cases. That also mea…

[deleted]

Re: Toshiba device tests cancer types from a drop of blood

#43

Post by bduerst »

_Microft wrote: post #19
BiteCode_dev wrote: post #14

Earlier quoted context omitted.

If it's very cheap, fast and convenient, then it's enough for at least screen the population regularly. Catching only part of the cancers is quite nice already.

No, not necessarily. Check out these numbers: Sensitivity is what fraction of the affected people are actually found. Here: 90%, so 10% are missed. Specificity is what fraction of the unaffected people are detected as such. Here: 95%, so 5% wrongly detected ("false positives"). In Europe, there are 60 cases of lung cancer per 100 000 people. That makes 54 correctly detected per 100 000, missing 6 cases. That also mea…

Cancer diagnostics do not rely on a single test. There's a number of (more expensive) metabolic and endocrinology panels, imaging, biopsies, etc. that follow to validate.

The idea is that you have something cheap and easy up front before or in parallel to further downstream diagnostic procedures.

Re: Toshiba device tests cancer types from a drop of blood

#44

Post by koolba »

_Microft wrote: post #19
BiteCode_dev wrote: post #14

Earlier quoted context omitted.

If it's very cheap, fast and convenient, then it's enough for at least screen the population regularly. Catching only part of the cancers is quite nice already.

No, not necessarily. Check out these numbers: Sensitivity is what fraction of the affected people are actually found. Here: 90%, so 10% are missed. Specificity is what fraction of the unaffected people are detected as such. Here: 95%, so 5% wrongly detected ("false positives"). In Europe, there are 60 cases of lung cancer per 100 000 people. That makes 54 correctly detected per 100 000, missing 6 cases. That also mea…

Is there “error” for these these tests independent when performed on the same person spaced out over a long enough time period?

Say you run the test every day/week/month, can you look at the total results or do the failure cases for the tests themselves depend on the individual?

Re: Toshiba device tests cancer types from a drop of blood

#45

Post by geoelectric »

_Microft wrote: post #19
BiteCode_dev wrote: post #14

Earlier quoted context omitted.

If it's very cheap, fast and convenient, then it's enough for at least screen the population regularly. Catching only part of the cancers is quite nice already.

No, not necessarily. Check out these numbers: Sensitivity is what fraction of the affected people are actually found. Here: 90%, so 10% are missed. Specificity is what fraction of the unaffected people are detected as such. Here: 95%, so 5% wrongly detected ("false positives"). In Europe, there are 60 cases of lung cancer per 100 000 people. That makes 54 correctly detected per 100 000, missing 6 cases. That also mea…

And that's assuming that the 99% accurate really means 99% sensitive, 99% specific.

To amplify your point,

99% sensitive from 100000 people with an incidence of 60 means 1 false negative, assuming you can't detect .4 of a person and floor to integer.

99% specific from the same pool means 999 false positives, same assumption.

You mentioned that re: 1000 total, but the kicker:

Total population, 59 true positives + 999 false positives.

So, if I test positive, absent any more knowledge that means it's a 59/(999 + 59) chance of being true, or around a 6% chance of being true.

Probably enough for followup testing, but an interesting demo of why the statistical accuracy is meaningless unless you also know the actual incidence. 99% becomes not many % right quick.

Re: Toshiba device tests cancer types from a drop of blood

#46

Post by nugget »

refurb wrote: post #34
_Microft wrote: post #19

Earlier quoted context omitted.

No, not necessarily. Check out these numbers: Sensitivity is what fraction of the affected people are actually found. Here: 90%, so 10% are missed. Specificity is what fraction of the unaffected people are detected as such. Here: 95%, so 5% wrongly detected ("false positives"). In Europe, there are 60 cases of lung cancer per 100 000 people. That makes 54 correctly detected per 100 000, missing 6 cases. That also mea…

Yup. And some of those follow on tests could be quite invasive and risky in their own right. With that kind of false positive rate, you'd be risking the life of a not insignificant number of people. Either that or driving up healthcare costs significantly as those 5000 people are going to need an MRI or CAT scan or something else to rule out cancer.

What follow on test for suspected lung cancer would risk the life of a not insignificant number of people?

An MRI without contrast has no impact. An MRI with contrast has relatively little impact. A biopsy would only be done if the MRI with contrast lit up areas of concern. At the point a PET is ordered, you have narrowed the false positive pool substantially and probably want the scan no matter what.

Re: Toshiba device tests cancer types from a drop of blood

#47

Post by mirimir »

refurb wrote: post #34
_Microft wrote: post #19

Earlier quoted context omitted.

No, not necessarily. Check out these numbers: Sensitivity is what fraction of the affected people are actually found. Here: 90%, so 10% are missed. Specificity is what fraction of the unaffected people are detected as such. Here: 95%, so 5% wrongly detected ("false positives"). In Europe, there are 60 cases of lung cancer per 100 000 people. That makes 54 correctly detected per 100 000, missing 6 cases. That also mea…

Yup. And some of those follow on tests could be quite invasive and risky in their own right. With that kind of false positive rate, you'd be risking the life of a not insignificant number of people. Either that or driving up healthcare costs significantly as those 5000 people are going to need an MRI or CAT scan or something else to rule out cancer.

That's also why there was no screening for thyroid cancer after above-ground nuclear weapons testing. Thyroid cancer itself isn't that hard to treat. So the risk of follow-on testing outweighed cancer risk.

Re: Toshiba device tests cancer types from a drop of blood

#50

Post by nugget »

koolba wrote: post #44
_Microft wrote: post #19

Earlier quoted context omitted.

No, not necessarily. Check out these numbers: Sensitivity is what fraction of the affected people are actually found. Here: 90%, so 10% are missed. Specificity is what fraction of the unaffected people are detected as such. Here: 95%, so 5% wrongly detected ("false positives"). In Europe, there are 60 cases of lung cancer per 100 000 people. That makes 54 correctly detected per 100 000, missing 6 cases. That also mea…

Is there “error” for these these tests independent when performed on the same person spaced out over a long enough time period? Say you run the test every day/week/month, can you look at the total results or do the failure cases for the tests themselves depend on the individual?

Many diagnostic blood tests for cancer markers are more useful as a data series over time than as single point in time tests, because individuals have variable "normal" or baseline levels. You establish an individual baseline for each marker (for each patient) and then re-test every 6 months. If a number moves from its baseline, then you investigate.
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