Test 3: APTT

Question 1

How does the anticoagulant sodium citrate prevent coagulation?

Answer 1

by chelating the Ca in whole blood, thus preventing it from being available to the coag cascade.

After centrifugation, the remaining plasma contains all intrinsic pathway coagulation factors except for Ca (& platelets)

Question 2

The APTT tests for deficiencies of all coagulation factors except…

Answer 2

Factors 3, 7, & 13

Question 3

PTT should NOT be used to monitor ____________ therapy.

Answer 3

LMWH

Question 4

The APTT is also useful for detecting the presence of circulating _______________, and for monitoring the effects of relatively low levels of unfractionated heparin (UFH) therapy.

Answer 4

anticoagulants (inhibitors)

Question 5

what is needed for PTT test?

Answer 5

1. Activated cephaloplastin reagent (Alexin/Actin/Thrombosil)
2. Calcium chloride reagent
3. Normal (Level I) and abnormal (Level III) Coag. controls
4. Patient samples (Na Citrate samples) 9. BFT II cuvettes
5. BFT II Analyzer
6. Automated pipet & tips
7. Kim-Wipes

Question 6

Patients with Hcts > ____ or < _____must be…redrawn with a corrected amount of blood & anticoagulant

Answer 6

50, 20

Question 7

what is the normal range for PTT?

Answer 7

25-35 seconds

Question 8

APTT is primarily used in the clinical laboratory to monitor…

Answer 8

unfractionated heparin therapy.

Question 9

The therapeutic range for heparin causes the APTT to run about ____ times the upper limit of normal. (“therapeutic goal” for heparin).

Answer 9

2

Question 10

The APTT is also used as a screening procedure for the determination of ________________ deficiencies (Factors 12, 11, 9, 8, 10, 5, 2, & 1), & also for detection of the presence of natural or acquired circulating inhibitors.

Answer 10

intrinsic Pathway factor

Question 11

Incubation of the patient plasma at 37oC for more than 5 min. may decrease Factors __________ thus prolong the clotting time, making it invalid (same for PT test.)

Answer 11

5 & 8, &

Question 12

When a APTT exceeds ______ sec., the test may be stopped & results reported out as “ > _____ sec.”

Answer 12

100

Question 13

Prolonged PT or PTT results mean either….

Answer 13

1. A coag factor is deficient
2. A natural or acquired anticoagulant is present

Question 14

Once the PT/PTT pattern result has been identified, “___________ studies” may be done to narrow down
the problem.

Answer 14

mixing

Question 15

Typically ___:___ mixing studies are done with normal plasma & the patient sample.
Since normal plasma contains all coag factors, any factor deficiency should correct when mixed
with it!

Answer 15

1:1

Question 16

If PT &/or PTT corrects with normal plasma (mixing study), what should be done next?

Answer 16

Go on to specific factor assays

Question 17

If PT &/or PTT does NOT correct with normal plasma (mixing study), that means…

Answer 17

A circulating anticoagulant must be present (either natural or acquired) & must be investigated further.