https://testdirectory.questdiagnostics.com/test/test-detail/...

Practically a lab tech who works under their franchise would have a book with instructions to do the test and would have a fair chance of doing it accurately with 10 tries, a good chance of doing it accurately within 100 and not-quite-certainty of doing it accurately within 1000 tries.

According to the that page the test requires that your blood be frozen to -70 C after drawing. They can do that a hospital but not at your Dr.'s office.

The current Vitamin C test is based on HLPC, there was something else used prior to 2000 or so which is not comparable to the current test.

The researchers could do that right but they could easily do it wrong. That's why "double blind" is important, it doesn't just test the hypothesis but it tests the tests.

Also it is shocking how little questions such as "baseline vitamin C levels in the population" are researched. It is going to be variable in specific populations (e.g. people who show up sick at your clinic) because it is depressed by tobacco smoking, affected by dietary intake, etc. For a hospital with a 100,000-patient customer base sampling 1,000 patients might establish a good baseline. A fair price for that test seems to be $40, so it is $40,000 to get that baseline, just 40 cents per customer. The challenge is to get it all in one place while there are thousands of other not-FDA-approved tests that might turn up interesting results that compete for it and where everyone thinks we spend too much already.