Can somebody provide tl;dr of what was wrong with their tests and how come they got this far if the tests were flat out wrong? Did they just used low precision tests and pass them as high precision or some such?
The main criticism from outsiders all along has been that blood drawn from a pin-prick just has too much variability for reliable blood testing. Which in turn means that Theranos’ approach to blood testing was never going to work for anything quantitative - it might be OK for 'is this chemical present or not' but not for anything else.
They spent a long time using traditional blood tests alongside their pin-prick versions (this is the service they were selling to Walgreens(?) - presumably they used their investor cash to subsidise the service & undercut their more traditional competitors) whilst trying to get the pin-prick to work but they couldn’t even manage to do those correctly.
How they managed to get this far is a question of hubris and investor gullibility. There’s also the possibility of outright fraud, but we don’t know if that was the case at this point.
If this is the case, why the hell are we using it for blood sugar level testing in diabetic patients?
Sugar is present in sufficient quantities that the variation you get from one pinprick to another isn't going to be a big deal.
Many other things will be present in small enough concentrations that even if it is present in your blood you might not have sufficient quantities for it to be detectable in blood from a single pin-prick.
Because it obviously works for sugar level testing, but not for the kind of tests Theranos claimed to do?
Case in point. Major companies like roche and abaxis have had point-of-care medical devices that perform blood testing for various parameters that use a drop of blood.
Theranos's problem was that they said they could do pretty much every parameter under the sun, and they used an FDA loophole to operate their lab. It was later discovered that 90% of the tests were not being processed with their supposed technology.