Being blood, it always looks like more than it really is. To illustrate have you ever seen someone with a bloody nose. It seems like blood is just everywhere, on the person’s clothes, hands, and face. But of course the person is not loosing a tremendous amount of blood, it just looks that way. Or did you ever cut yourself and didn’t realize it until you saw blood on your shirt or on an object you just touched? You say to yourself, “Where is all this blood coming from!” Then you finally realize the blood is coming from you and it might only be a small cut on your finger perhaps- no need to call the ambulance. So, during a blood draw as you see the different vials being filled with your blood, it looks like a lot. It may even make you feel uncomfortable watching. We just are not use to seeing our own blood fill one vial after another. But you can spare it, it really isn’t very much. Don’t worry you won’t faint do to blood loss. But why are multiple tubes sometimes needed. Can’t only one blood vial suffice? Not always.
Several Vials Needed?
The medical laboratory doesn’t always need that much blood, but they have to take it that way for several reasons. They sometimes take several different vials because each vial has a different preservative or anticoagulant. Anticoagulant is the preservative found in most blood collection vials that prevent the blood from clotting. They’re marked with different colored tops. Each test might require a different colored vial. For example, you cannot test for cholesterol off a lavender colored tube but you can run a CBC (complete blood count) off it. The cholesterol test needs a red top tube. Are you with me so far? So, the phlebotomist will look at the prescription order and know to draw a red top and a lavender tube. The same tube can’t be used for both tests. Since the preservatives and anticoagulants can interfere with some tests, they need to take different vials for different tests.Every laboratory has there own guidelines as to what tests go with what tubes. But generally there is an industry standard.
What is a QNS?
They don’t need all of the blood they take in each vial, but they generally have to fill the vials to ensure the proper ratio of anticoagulant to blood. Take less and it throws off the tests. A laboratory can reject a blood vial for what is called a ‘QNS’ which means ‘quantity not sufficient’. So, to insure that doesn’t happen the phlebotomist will try to fill the tube even if only one test is being run off it. Each test only requires a tiny amount of blood. A laboratory can run several tests from one full vial (granted all the tests have the same requirement). Each test may take less than 1 ml, but they add up quickly.
More understandable now, right? It isn’t that complicated after all. You just need someone to break it down in simple terms. Don’t we wish we had a little guide to refer when we get blood tests done.