I don't believe they could run a battery of 81+ tests on a drop of blood. There simply isn't enough there. Why do you think they take tubes of blood for testing, currently?

The issue is concentrations and the presence of them in sufficient amounts to be detected reliably and consistently.

edit: typo.. words are hard.

It's because that's what the equipment is designed to use, and yes it provides more reliable results with the current technology. Much of the equipment used in healthcare relies on very old technology. This certainly does not mean it cannot be improved to work with less amount of material.

There are hand held sequencers for your phone now (minIon) that are very cheap and work. There are also large multimillion dollar bench top machines on the same technology from nanopore. Both are very new technology compared to what we used in early 2000s, and offer various different features and certainties from the analysis.

However, it is foolish to say that the minIon is impossible. It works. It's just less resolute than other systems.

This is true for many systems which people cry "Theranos" about. Their issue was lying. That was the problem.

Less resolute works in some cases and that was never at issue. The problem is, less resolute doesn't work for some things and when the sample size is a drop of blood, we're talking insanely small, as in impossible, sample size for some tests.

Low concentrations will NOT be reliably detected. That's part of why such a comparatively large sample is taken when you go for the traditional testing.

I'm not even going into the simple fact that once chems are introduced into the sample to generate reactions, the sample can't continue to be used.

Exactly how many times do you think we can split a single drop of blood?

Edit: good talk, even if we disagree. :)