I mean, why can’t they stab some part of you that doesn’t have as many nerve endings, like the back of your hand?
I’ve asked this to several phlebotomists when I donate blood, and I got the following unsatisfactory replies:
The skin is thinnest there
It’s the most accurate place to measure
It’s in our SOP
Number 1 makes no sense. Granted, I’ve been working soft jobs, but surely the little stabby thing they have would make me bleed just as well if you jabbed me in the arm.
Number 2 also makes no sense. Iron isn’t being consumed by the tissues like glucose. It’s level should be the same whether you get blood from the finger or the lung. And exactly how accurate do they need to be when they are just dumping the blood drop in solution to see if it sinks?
Number 3 is just stupid. We do it because we do it. Lame.
While we are at it was there ever a reason to do it from the finger for glucose? When I was a kid in Russia I once had my sugar levels plotted in four hourly tests… Each required at least two pricks because my body sucks at bleeding when under stress. Now, was that really necessary? Couldn’t they just use some part of me that doesn’t have an obscene number of concentrated nerves due to being, you know, the tactile sensation extremity and all?
For a while at least some were using an ear lobe which was virtually painless and I was sorry to see them go back to the fingertip. I asked and got some canned response about it being more accurate.
I hope you get a satisfactory answer to this because I’ve never understood it either. I don’t have any problems with shots but I tremble for hours after getting a finger stick.
I usually did the lobe thing when dealing with an infant whose veins are too tiny to hit.
Hell, come to think of it, I’ve done Complete Blood Counts that way. That consists of a Red Cell Count, White Cell Count, Hemoglobin, Hematocrit, and a Differential (this last, the ratio of the various white cells in the blood).
As it was explained to me regarding finger sticks for blood glucose, they’re looking for capillary blood, where you’ve got a high level of interaction between the blood vessel and the cells surrounding it, so you have some idea of how much oxygen and other stuff is getting carried by the blood, as well as how much is being transferred back and forth through the vessel wall. You only really find this in capillaries; in larger vessels, the blood is just travelling from point a to point b and isn’t involved in any other bodily processes.
So, why the fingertip? Lots of capillaries and therefore a good chance to be able to draw blood with a fairly minor wound. Other places with lots of capillaries include the toes and the penis. Not so desirable for a great many people; you can avoid using the finger that just got stuck, but if you have to walk out of the office, it’s hard not to use the toes. Most people have fingers, and they’re all readily available.
There’s also a psychological factor to consider–a lot of people want to watch what you’re doing, and having somebody approach the side of your head with a sharp, pointy thing is going to freak some people out.
A fingertip is much easier to maneuver than an earlobe. Having done several fingerpricks as a lab tech, I’ve perfected a firm finger-holding grip. It’s important to be able to hold the hand still, because the person will usually flinch as the lancet jabs the skin. Not so easy to hold a head perfectly still. It’s also easier to bring finger and glucometer test strip together if you can change the angles of both while you’re working. Lastly, band-aids don’t fit so well on ear lobes.
Maybe they got tired of smartasses like me, who answered the question about getting ear piercings with, “No, the only ear piercing I ever had was right here.”
As for the Band-Aid® fitting the finger better, pfft. My blood center uses little round ones, and they don’t fit my fingertip any better than my earlobe.
They got you with psuedo-BS. All of your skin has capillaries. Oxygen doesn’t diffuse well through more than 3 cell thicknesses, so pretty much every cell in your body is no more than three cells away from a capillary. When you take into account the fact that one of these 3 has to be the cell that make the blood vessles themselves, you’re left with a damned lot of capillaries needed.
Now, maybe the finger tip has more than usual, but that doesn’t explain why a sample can’t be taken just as easily from the back of the hand or the arm. Taking a sample there would also solve the grippability problem of earlobes.
True, but the epidermis itself has no capillaries, so if you want to be able to get at them easily and efficiently with a prick, you want to go where the epidermis is thin. The fingertip is the most easily-accessible area of high capillary density under very thin skin. The earlobe fits the bill well enough, but procurement of a blood sample from the earlobe is more complicated.
You can, of course, manage to get a blood sample from any spot of skin, if you really want to. But it’s a question of easy access and simplicity to just use the fingertips.
And that’s probably why they use it. I’m just annoyed that my comfort isn’t a factor in their equation. They stuck me in the arm with a 16 gauge needle for 15 minutes, but it’s the nanosecond pinprick in the finger that hurts all day. I’m also peeved by the canned answers I got from techs, answers which they probably knew were lame.
And the fact that they’re probably thinking me as another one of those annoying clients who can’t just stop asking silly questions.
I was doing lab work in the 50’s-60’s, and when it came to pricking a patient, I always gave them a choice. Finger, ear lobe, whatever. (But it never occurred to me that one’s penis is an option. )
I’m sorry you were victimized, Pullet. I mean it. There are so many horse’s asses in the lab.
How come you avoided a heelprick? I’ve always followed the practice that the heel was the easiest and least traumatic place to try and draw blood from an infant.
