USMLE Coagulation Panel in DVT Patient

[drcasey12]

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I am confused about the results from a coagulation panel in a patient diagnosed with DVT due to hypercoagulation caused by factor V leiden.

So PT, INR, aPTT are all normal. D-Dimer is nearly triple the normal value (which is expected).

My question is, why are PT, INR and aPTT not lowered or abnormal? My reasoning is that the hypercoagulation would cause faster rates of clotting.

Any help is appreciated. Thanks

 

[seminoma]

Factor V leiden doesn't change the rate of coagulation. It can't be inactivated by protein C/S so clotting continues.

 

[drcasey12]

Factor V leiden doesn't change the rate of coagulation. It can't be inactivated by protein C/S so clotting continues.

I see what you're saying, but the diagnosis is "hypercoagulation." So coagulation has changed by increasing over normal baseline, which is why the d-dimer has increased. What I'm wondering is why PT, INR, aPTT haven't specifically changed.

 

[drcasey12]

I'm wondering if anyone else may also chime in to provide some insight? 🙂

 

[scoKraz4]

Maybe it is just a clinical diagnosis. Those pathways shouldn't be any faster or slower. Just more potent?

 

[seminoma]

I see what you're saying, but the diagnosis is "hypercoagulation." So coagulation has changed by increasing over normal baseline, which is why the d-dimer has increased. What I'm wondering is why PT, INR, aPTT haven't specifically changed.

D-dimer has nothing to do with hypercoagulation. D-dimer just indicates fibrin breakdown.

 

[dfib slim]

I see what you're saying, but the diagnosis is "hypercoagulation." So coagulation has changed by increasing over normal baseline, which is why the d-dimer has increased. What I'm wondering is why PT, INR, aPTT haven't specifically changed.

D-dimer will be increased with a DVT with or without factor V leiden. Just because you have factor V leiden and in a hypercoagulable state doesn't mean you're throwing clots left and right or consuming all your coag factors like in DIC. Maybe a DVT is small enough to not lower your coag profile?

 

[tropocollagen]

My understanding to factor V leiden is that the mutated factor V only affects clot break down (anticoagulation) while has no/little effects on clot buildup (coagulation). So PT, INR, aPTT are all normal as they are all measurements of how fast the clot forms.

 

[drcasey12]

Thank you @tropocollagen, @dfib slim ,@seminoma, @scoKraz4 very much for all of your help! You guys really cleared up a lot for me!