What’s the difference between serum and plasma?
Q. Quick question for you about serum vs. plasma: I wrote in my notes during class that serum is plasma without the clotting factors. (more…)
Q. Quick question for you about serum vs. plasma: I wrote in my notes during class that serum is plasma without the clotting factors. (more…)
Q. I was reviewing for boards and had a question about blood types and pregnancy. (more…)
Here is a good question from one of our readers: “Why is blood group O+ not a universal donor?”
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Q. I have a quick question about coag lab tests. In the tests that you are adding phospholipid (like the PTT), what exactly is the phospholipid doing?
A. It’s just providing a surface for the coagulation factors to sit on! Many of the coagulation factors need a phospholipid surface to sit on in order to work.
Normally, the platelets provide that surface (they have phospholipids in their membranes) – but you’ve taken the platelets out of the test tube before you do the coagulation lab tests – so you need to add them back in if you want the whole cascade to run.
You also add phospholipid in the PT (INR)! It’s part of the thromboplastin molecule. Thromboplastin is just a tissue-factor-like substance plus phospholipid, all wrapped up in one reagent.
A few of the coag tests don’t require a phospholipid surface. The TT, for example, doesn’t need phospholipid; you’re just adding thrombin and seeing how fast it can convert fibrinogen to fibrin – and that single reaction doesn’t need phospholipid to work. Also, the fibrinogen assay doesn’t require phospholipid because it just measures the amount of fibrinogen.
Q. I have one question, and you are my last hope. What is the difference between the absolute and corrected reticulocyte count? (more…)
This song by TheMashedPotatoMan is a hilarious and memorable reminder of one very important aspect of the D-dimer assay, which is this: (more…)
Janarthan sent in a great question on one of our posts about the two coagulation paths: the intrinsic and extrinsic pathways. (more…)
Q. About the red cell distribution width (RDW), I don’t understand it! (more…)
Here’s a great question from a reader:
Is it normal to have a prolonged bleeding time but a normal PTT? (more…)
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