Elevated PTT

Question 1

What does PTT measure

Answer 1

partial thromboplastin time measures the intrinsic and common pathway. therefore,

prekallikrien, HMWK, factors 12, 11, 9, 8, 10) as well as 10, 5, 2 (prothrombin/thrombin) and fibrinogen are measured by PTT

Question 2

to perform PTT, plasma is exposed to :

Answer 2

a thromboplastin that does not have tissue factor activity, and a negatively charged, activating substance, which initiates coagulation via the intrinsic clotting pathway.

Question 3

the PTT is the mite measured in ____ for a ___ clot to form

Answer 3

measured in seconds for a fibrin clot to form.

Question 4

describe a study that can help identify the cause of an elevated PTT

Answer 4

mixing study. do a PTT on a concoction of pt plasma and normal plasma

• if the aPTT prolongation corrects on mixing due to replacement of factors from the normal plasma, the prolongation is likely due to a factor deficiency
• if the patient has an anti phospholipid antibody or an antibody directed toward a specific coagulation factor (thus a factor inhibitor), the aPTT will remain prolonged.

Question 5

a deficiency or inhibitor to any of the clotting factors except ___ can be associated with an elevated PT

Answer 5

except factor 7, which is part of the extrinsic pathway.

Question 6

which factors of the intrinsic pathway are measured by PTT but are not associated with bleeding symptoms?

Answer 6

Pre-kallikrien, HMWK and factor 12.

Question 7

Problems with factors __, __, __< and ___ will be associated with elevated Pt and PTT

Answer 7

2, 5, 10, and fibrinogen

Question 8

the presence of ___ ___, which include the Lupus anticoagulant, can be associated with prolonged PTT and rarely an elevated PT

Answer 8

anti phospholipid antibodies.
these are auto antibodies which interfere with assembly of clotting factors on surface ofphospholipid vesicles in the pTT testing reagne that results in aPTT prolongation.

APLA may activate platelets by interacting with phospholipids on the platelet surface an may result in venous and arterial thrombosis as well as pregnancy loss.

Question 9

how to test for APLA?

Answer 9

mixing study to confirm the presence of an inhibitor, then perform the PTT using different types and concentrations of phospholipid in the testing reagent. If the pTT corrects with the addition of phospholipids that are incentive to lupus inhibitors or with the addition of excess amount of phospholipid, is confirms the presence of a lupus inhibitor.

Question 10

PTT is used to monitor the degree of anticoagulation for patients who are on ___ ___ therapy. why

Answer 10

unfractionated heparin (IV heparin) therapy. UFHep is an indirect thrombin inhibit that forms complex with antithrombin, converting antithrombin from a slow to a RAPID inactivator of thrombin and 10a. the therapeutic value for patients receiving heparin is an aPTT of 1.5 times the upper limit.

Question 11

t/f lmwheparin and warfarin increase PTT

Answer 11

false. warfarin inhibits vitamin K, which are responsible for the carboxylation of factors 5, 7, 9, 10 + fibrinogen.
although 9 is part of the intrinsic pathway, 7, 5, and 10 are common pathway, so it would likely overwhelmingly cause a higher INR/PT measurement.

Question 12

T/F lupus inhibitors would present with a high pt

Answer 12

false. just the ptt. also doesn’t inhibit clotting factor function there no bleeding symptoms, it just causes thrombosis due to excess platelet activation
LOOK FOR OTHER CAUSES IF EXCESSIVE BLEEDING IS A SYMPTOM– APLA DOES NOT CAUSE ELEVATED PT OR BLEEDING.