Skip to 0 minutes and 9 seconds In the course we look at the ELISA and Western blot techniques, which are used, in the case of ELISA, for detecting antibodies against viruses. And, in the case of Western Blot, for directly detecting the viral antigen on the gel. The starting point for both of these techniques is a blood sample from the patient. So today I’m joined by Martin Reynolds, who is a medical student at Lancaster Medical School, who will be showing how a blood sample is taken from a patient. In this case, the patient will be me. So, Martin has previously washed his hands using the Ayliffe technique. So his hands are considered to be clinically clean.
Skip to 0 minutes and 45 seconds And he’ll be putting some gloves on, as well, for extra hygiene precautions while taking the blood sample. I should, of course, add that blood samples are only taken by health care professionals. So this is purely for demonstration purposes, and you ought not, of course, to be trying to do this for yourselves. So what we have here is our Vacutainer kit. We’ve got our tray, which has been cleaned with an alcohol wipe before use. We’ve got a grey tourniquet down here, which we’re going to put around Derek’s arm. This will dilate the vessels in his arm, and we’ll be allowed to access them much easier that way.
Skip to 1 minute and 19 seconds We’ve also got a needle, which is this green component here, attached to this clear bottle. This, we haven’t unsheathed this yet, because it would be unsafe to do so. We don’t want sharps waving around where they can hurt people. We’ve also got our yellow bottles, which we collect the blood in. These are pressurised, so they have easier access to the blood, and we’ll be able to get the blood out much easier. We’ve also got the top there. We’ve got an alcohol wipe. And we’ve got some gauze there, just to clean up any blood, if that was to spill anywhere. First things first, I need to wash my hands. I’m going to use the Ayliffe technique to wash my hands.
Skip to 1 minute and 56 seconds So Martin has got his gloves on, and he’s going to apply the tourniquet to my arm here. So we’ll see if I can get a decent sized vein up for venipuncture. I’ll just try to–
Skip to 2 minutes and 10 seconds Yes, we’ve got a nice one coming up just here. You can just see there. You might not be able to see this on the video. It’s a very generous description of a nice vein, it has to be said. Loosen that off now. Just loosen that slightly. Just while we clean. We don’t want to keep the tourniquet for too long, because it is a little bit too painful.
Skip to 2 minutes and 30 seconds Just give that a clean. OK, so I’m just going to unsheath the needle now. I’m going to need the needle to be facing bevel up. Just going to anchor the vein distally. And now I’m just going to insert this. I’m just going to warn you Derek, you’re going to feel a sharp scratch there. OK. So there it goes, that’s it in now. Because it’s at negative pressure, when Martin inserts this, you see it rapidly start to fill up with my blood. There we go. So that’s the pressure just released. And the blood is now moving into the tube. So you notice that this actually separates the collection of the blood from the entry of the needle.
Skip to 3 minutes and 11 seconds And again, here it comes out, and the blood is in the tube. You’ve got a full tube. That’s now ready for use. So that can go for one of our ELISA reactions. We could do the same again. So, say for instance, we wanted to do an ELISA and a Western blot, we’d have one blood sample for the ELISA reaction, and another one for the Western blot. OK, hold on now. I think that will do for blood collecting, so we’ll loosen that off. Releasing the tourniquet. Take the bottle out. Trying not to move the needle at all. Give that a few twists. Then I’ll get my gauze.
Skip to 3 minutes and 44 seconds So the needle comes out now.
Skip to 3 minutes and 49 seconds I just press on that to preserve my best shirt for the next session. OK, we’re all done.
Taking a blood sample
In this video, Lancaster University medical student Martin Reynolds demonstrates how to take a blood sample.
The blood sample could be used for the techniques demonstrated in the next section - ELISA and Western Blotting.
In the modern technique for phlebotomy (taking a blood sample), depressurised “vacutainers” are used. The needle is inserted first, and then the vacutainer connected to the needle. This releases the vacuum and a fixed volume of blood is sucked out. There are no syringes and bottles, as were used in the classic technique.
As with the nasopharyngeal swab - PLEASE DO NOT TRY THIS AT HOME.
The sample taken will then be used for the next stage - diagnosis of the presence of viral antigen (indicating an on-going virus infection) or the presence of antibodies to virus (indicating previous exposure to the virus).
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