hemophilia B

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Shouldn't the PT be elevated in hemophilia b since it is a factor 9 deficiency?

Originally Posted by koreanguy

Shouldn't the PT be elevated in hemophilia b since it is a factor 9 deficiency?

PT is really only defined by Factor 7 activity.

Factor 9 is part of the PTT pathway.

PTT = you play table tennis indoor (12 11 9 8)
PT = you play tennis outdoor (7)
10 5 2 1 are factors of each other.

Yeahhhh

Originally Posted by koreanguy

Shouldn't the PT be elevated in hemophilia b since it is a factor 9 deficiency?

PT tests extrinsic pathway factors. Factor IX is part of the intrinsic pathway, and thus will be tested via PTT.

Originally Posted by mdeast

PT is really only defined by Factor 7 activity.

Factor 9 is part of the PTT pathway.

PT tests Factor VII but that's not the only thing it tests. PT actually tests factors I, II, V, VII and X.

Originally Posted by IDoIt4Love

PT tests Factor VII but that's not the only thing it tests. PT actually tests factors I, II, V, VII and X.

Correct, because the conversion of prothrombin (II) into thrombin (IIa) will convert Fibrinogen into Fibrin. The "Prothrombin Time" is the time that it takes for prothrombin to stay in solution (not converted). So, everything before conversion of the fibrinogen to fibrin, by thrombin, is PT.

The assay is done by adding TF, phospholipids, and Ca++ to the plasma.

But it's easier to remember 7, and then 10 5 2 1 -> clot (detected optically) is common.



In testing APTT, you *ADD* phospholipid + Ca++ + activator. The time phospholipid + Ca++ (partial thromboplastin (thromboplastin is phospholipid + TF, whereas partial is without TF)) remains in solution without forming a clot is the time it takes for 12 11 9 8 to come together and cleave 10 5 2 1 -> clot (detected optically). Note that TF is NOT used.