Critique of Mark Cuban's blood testing plan and his critics

A rip-roaring debate broke out on Twitter a couple of weeks ago spurred by a series of tweets advocating more blood testing from the entrepreneur, Shark Tank investor, and billionaire owner of the Dallas Mavericks Mark Cuban:

Cuban is proposing regular (quarterly) blood tests (i.e. screening) even for healthy individuals. He argues that the concentration of various biomarkers in your blood can provide a baseline against which to measure any changes caused by some potentially harmful perturbation. If you have enough data, then subtle changes in specific biomarkers could indicate the impending onset of a disease such as cancer. The thinking behind this idea is similar to the motivation of Project Baseline of Google which I described in an earlier post:

"Another approach would be to collect a wide spectrum of biomarkers from healthy people and then use this set as a reference to compare both healthy and non-healthy people. This strategy may allow the identification of pre-disease states and a finer classification of disease states....

The project will yield thousands of new biomarkers evaluated in thousands of people, who will be tracked over time. In this way, changes in the biomarkers may give an indication of the early onset of a disease or even a pre-diseases state. Instead of using one biomarker to determine the presence of a disease, a range of biomarkers could be used to describe the onset, progression, and severity of a disease along with the efficacy of various treatments."

Cuban's proposal seems to have no downside, but there was immediate pushback from a variety of medical experts. The healthcare journalist Charles Ornstein raised the concern that too much screening can yield negative consequences:

What are these downsides of excessive screening? The problems are from false positives when the screen misidentifies a person as positive for a disease when they are actually negative (i.e. don't have the disease). Any screening method is not 100% accurate, and so false positives will arise at some (low) frequency. But this misidentification can lead to costly and harmful procedures for the patient. It is a prominent issue in both breast cancer screening and prostate cancer screening, and has raised debate over the net benefit of both mammograms and PSA tests.

Dan Diamond mentions in an article how prostate-specific antigen (PSA) blood tests are used to diagnose prostate cancer. Although the false positive rate is low in this test, so also is the mortality rate. For example, out of 1000 elderly male patients, over a 10 year period approximately 8 will die of prostate cancer with or without PSA screening, whereas in the screening group another 20 will be false positives who are incorrectly diagnosed and unnecessarily treated.

One can imagine that with extensive biomarker screening and numerous tests that the absolute number of false positives could be rather high even with an extremely low false positive rate just because there are so many tests. This could to lead to countless unneeded followup diagnosis and treatment procedures.

Mark Cuban makes the important point, however, that the testing would give the patient more information, including information about the reliability of the test. The problem is that humans are not very good at understanding medical risk and so the natural tendency would be to become freaked out by a false positive instead of perhaps waiting and getting re-tested at a later time.

Also in defense of Cuban, his plan represents the future of medicine. These screening tests will improve to the point that they can be used reliably with a clear net benefit. Indeed getting more patient data will help them improve. Indeed, one can argue that we are moving to a (distant) future of not quarterly blood tests, but real-time blood monitoring.

However there is a considerable tension between what is the reality now versus the ideal of the future, as well as the tension between the standardized medical care for the broader population versus the optimal healthcare for one particularly knowledgeable data-maximizing individual. The medical community makes rules that (hopefully) have a net beneficial outcome to the population as a whole when you weigh the overall costs versus benefits. Blood testing of healthy individuals does not fit this criteria because of the false positive problem.

Ultimately modern medicine will move beyond standardized rules aimed at the "average person" to more personalized diagnosis and treatment (e.g. Precision Medicine Initiative). This is the future Mark Cuban wants to hasten, but we are not there yet.