It appears this depends a lot on what you are testing for. Fingerprick tests for CRP count (basic inflammation test) seem to already be standard practice in hospitals and health clinics. The test machine is the size of a toaster and gives the physician direct results in a minute or two.<p>Also, for blood glucose, which diabetics need to monitor closely, there is some buzz now around spectrographic (IR&#x2F;UV) techniques, meaning you don&#x27;t even have to puncture the skin. That would be huge. Diabetics actually complain more about fingerprick tests for glucose than about insulin injections, which sounds very counter-intuitive to non-diabetics.<p>What glucose and CRP have in common is that they are small. TFA talks about tests for white blood cells, platelets or HIV, which are much larger. If you compare white blood cells to glucose, they have three orders of magnitude larger radius, so <i>nine orders of magnitude</i> larger volume.<p>That&#x27;s like the difference in volume between a raindrop and a blue whale. No wonder different mechanisms may apply.