Comment by pja | Hacker News Reader

Comment by pja | Hacker News Reader

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I don’t think anyone from Theranos has come out and said anything definitive publicly.

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.

I'm sorry but this is incorrect for a lot of blood tests. When the theranos debacle unfolded there was a paper making the rounds (no doubt leveraging on the media's attention)that argued this point for white blood cell counting. The conclusions were overblown, there is increased variability when using small amounts of capillary blood, but the tests are still useful. Furthermore, a lot of parameters are less sensitive to this heterogeneous distribution of the analyte.

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.

"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."

If this is the case, why the hell are we using it for blood sugar level testing in diabetic patients?

The issue is not that it can't be used for anything, but that what you use it for depends on how much of whatever you're looking for will be present in any given volume of blood.

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.

Going back to the white blood cell count. The gold standard is flow cytometry. If there is an interferent in the sample, or if the cytometer raises any flag, in some labs the backup plan is to do a manual count (100 cells) using whitefield microscopy ... are you really concerned about sampling problems?

I don't see how what you're saying relates to what I wrote.

Apart from what the other answer says, notice that diabetics get a pinprick every single day and that only exaggerated values (either low or high) are relevant. And then again, it is a very easy and simple procedure, for glucose, you do not need any fancy laboratory for this single test.

>If this is the case, why the hell are we using it for blood sugar level testing in diabetic patients?

Because it obviously works for sugar level testing, but not for the kind of tests Theranos claimed to do?

Consider that a glucose molecule is maybe 1.5nm in size, while a red blood cell is 6-8µm and a white blood cell is 12-15µm. Then consider that a capillary is 5-10µm in diameter. The cells actually deform to be able to fit through.

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