Detecting and Evaluating Coagulation Inhibitors and Factor Deficiencies Exam

Which of the following would be acceptable as the "normal" plasma reagent to use in a mixing study?

A pooled plasma from at least 20 healthy donors having normal PT/aPTT results Feedback An appropriate normal plasma would be prepared by pooling at least 20 plasmas from healthy donors having normal PT/aPTT results. A commercial product is also acceptable.

Which of these factors may be deficient if both the PT and aPTT are prolonged?

Factor II

You have just performed stat PT and aPTT tests on your coagulation instrument. Your results are as follows: PT = 12 seconds (normal range 10-13 seconds) aPTT = 24 seconds (normal range 21-34 seconds) What would be your next step?

Report the results

When performing your mixing study, you aliquot your sample plasma and the pooled normal plasma to create your "mix". You then place the mix in a water bath to incubate for 90 minutes before testing your new mixed sample. What is the problem with the steps involved in the procedure above?

You have not run a PT or aPTT on the new mix before incubating

A mixing study should be performed within what time frame following collection of the specimen?

4 HRS

Which of the following is considered one of the most common coagulation inhibitors?

Lupus anticoagulant (anti-phospholipid antibody)

What may cause the following mixing studies results? Initial aPTT = 133 seconds 1:1 Mix aPTT pre-incubation = 33 seconds 1:1 Mix aPTT post-incubation = 124 seconds

A slow acting coagulation inhibitor Feedback In this case, with the pre-incubation aPTT mixing study result "corrected" and the post-incubation aPTT mixing study result "not corrected", a coagulation inhibitor should be suspected. Both anti-factor VIII and lupus anticoagulant have been known to be slow-acting and can exhibit this result pattern. If a factor deficiency was present, we should not see a post-incubation prolongation.

ACQUIRED hemophilia A may be the result of which of the following conditions?

Anti-factor VIII inhibitor

Which of the following tests is used to quantify a coagulation inhibitor?

Bethesda assay

Which of the following actions would be appropriate for the investigation of an initially prolonged PT test? (Choose all that apply)

Check for clots in the sample Check patient history Check for anticoagulant therapy Feedback The first steps in determining the cause of prolongation should always be to check the sample integrity, check the patient history for liver disease, and ensure the patient is not receiving anticoagulant therapy. Canceling the PT test without investigation of the cause of prolongation is not advised as the patient may have an underlying problem that garners further investigation from the laboratory.

A patient has a prolonged non-therapeutic PT and a normal aPTT. The physician orders a PT mixing study. The results are as follows: Original PT test- 32 seconds 1:1 Mix (room temp immediate) - 22 seconds 1:1 Mix (incubated for 90 minutes) - 23 seconds Which factor may be present in abnormally low levels and causing the prolongation? Please select the single best answer

Factor VII

What MINIMUM level of a particular factor will cause the aPTT test to become prolonged?

Feedback A prolonged aPTT test result will occur only if one or more factor levels that are measured by this test are less than 40% of the normal level(s).

What may prevent the detection of lupus anticoagulant in a plasma sample if the blood used for testing is not centrifuged for a sufficient time?

Increased platelets in the plasma sample

A thrombin time will detect heparin in a patient's plasma so that heparin does not produce a false-positive aPTT mixing study result.

True