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pathoma: inconsistency on plasmin and D-dimer

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Oh_Gee

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on the 2017 edition pg 35, it says D-dimers "are derived from splitting of cross-linked fibrin"

on the same page it says "plasmin cleaves fibrin and serum fibrinogen..."

on pg 36, while talking about plasmin overactivity, it says "fibronogen is lysed, however, D-dimers are not formed because fibrin thrombi are absent"

i am confused. first he says plasmin cleaves fibrin but then it doesn't make d-dimers from that? why?

is it because he's talking about a disease state (plasmin overactivity) where it's assumed there are no fibrin thrombi
 

TheBoneDoctah

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on the 2017 edition pg 35, it says D-dimers "are derived from splitting of cross-linked fibrin"

on the same page it says "plasmin cleaves fibrin and serum fibrinogen..."

on pg 36, while talking about plasmin overactivity, it says "fibronogen is lysed, however, D-dimers are not formed because fibrin thrombi are absent"

i am confused. first he says plasmin cleaves fibrin but then it doesn't make d-dimers from that? why?

is it because he's talking about a disease state (plasmin overactivity) where it's assumed there are no fibrin thrombi

You are only going to see D-dimers if the fibrin is crosslinked. Plasmin cleaves fibrinogen, but since its not crosslinked, you won't get D-dimers.

This is how you can tell the difference between certain diseases. For example, in DIC you will see an elevated D-dimer because of the thrombi throughout the body that are being broken down.


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Oh_Gee

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You are only going to see D-dimers if the fibrin is crosslinked. Plasmin cleaves fibrinogen, but since its not crosslinked, you won't get D-dimers.

This is how you can tell the difference between certain diseases. For example, in DIC you will see an elevated D-dimer because of the thrombi throughout the body that are being broken down.


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fibrin is crosslinked fibrinogen, right? sattar says plasmin cleaves fibrin and fibrinogen
 

ASM student

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fibrin is crosslinked fibrinogen, right? sattar says plasmin cleaves fibrin and fibrinogen
It does, Coagulation cascade has to be activated for thrombin ( factor II) to cleave fibrinogen into fibrin. Fibrinogen is a normal serum protien but fibrin is found only clotted.

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TheBoneDoctah

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fibrin is crosslinked fibrinogen, right? sattar says plasmin cleaves fibrin and fibrinogen

Right, so when fibrinogen is cleaved you won't see d-dimers. To keep it straight in your head, you just need to remember that you will see d-dimers whenever you have crosslinking.


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Oh_Gee

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It does, Coagulation cascade has to be activated for thrombin ( factor II) to cleave fibrinogen into fibrin. Fibrinogen is a normal serum protien but fibrin is found only clotted.

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so in times of plasmin overactivity, there will be no d-dimers b/c there was no fibrin crosslinked clots in the first place? why can we assume that?
 

ASM student

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I'm not sure how the labs work here but I think there would be a normal range of variation that only a significantly increased process would be detected positive for it to be more specific.

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donovank730

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Important to remember in DIC you're forming pathologic thrombi, and than when the thrombi are cleaved you see D-dimer.

In fibrinolysis you never form the thrombi and therefore you never see D-dimer (just cleaved fibrinogen), you also don't use up platelets in disorders of fibrinolysis(cause your not forming thrombi) so you are going to have normal platelet counts as well(another important distinction)

the most important thing to keep in mind is whether there have been thrombi formed or not.
 
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