I've seen this argued over the past couple days on an alt Trek game well past TNG. This is a medical question regarding the canon of drawing blood for a physical.
We have one person (the doctor) who claims that blood draws are normal in a standard physical, using a hypospray, so that they can test for ailments that could not be picked up by biobeds, medical tricorders or any other non-invasive Trek tech. They say the tech cannot find the issues a blood draw can find and state that this is standard procedure so it shouldn't be a surprise to anyone. They also plan on keeping the blood on file.
We have another person (the patient) who claims that Trek tech allows for testing without the 'barbaric and archaic' uses of drawing blood, as drawing blood hasn't been necessary in a standard physical since the 23rd century. Also that drawing blood was only necessary in the cases of working out unknowns within the results of the scans, or in the case of verifying that the person was a changeling. (We'll ignore that the changeling thing has never worked, not a single time.) This person was also raised in the Romulan Star Empire, so already has trust issues.
There's very few physicals done in the canon shows, but those that I recall were very tech reliant, sitting on a biobed or in that special chair Bashir had.
In any case, it's starting to cause a little bit of drama and I wanted to check the collective thought on the canon of it. :)