A clinical laboratory receives a new lot of PTT reagent, so ...

[joblessjake]

A clinical laboratory receives a new lot of PTT reagent, so clinical laboratory scientists in the laboratory need to establish the heparin therapeutic range for this new reagent lot. How should this be done?
 
  a. Compare PTT results for patient heparinized samples to those for the lot of PTT reagent that is presently being used.
  b. Perform chromogenic Xa and PTT assays on patient heparinized samples, and do a statistical analysis of result comparisons.
  c. Add heparin at various therapeutic concentrations to normal plasma, and perform PTT on each concentration using the new lot of reagent.
  d. Add heparin at high concentration to one normal plasma, make dilutions of this plasma, and then perform PTT on each diluted sample using the new lot of reagent.

Question 2

Which of the following is true related to the use of aspirin to prevent cardiovascular disease?
 
  a. It is used to prevent arterial thrombosis.
  b. New studies show it is not effective.
  c. It works well but must be carefully monitored with monthly bleeding times.
  d. Aspirin monitoring tests such as thromboxane B2 are now easy to perform and widely available.

[cegalasso]

Answer to Question 1

ANS: B
Accrediting agencies for clinical laboratories require that the PTT heparin therapeutic range be determined using samples from patients who are receiving heparin therapeutically; they cannot be receiving simultaneous warfarin therapy (thus their PT must be normal). Both a chromogenic anti-Xa assay and PTT are performed on each patient sample, and the paired results are plotted in a linear graph. The range that corresponds to 0.3 to 0.7 chromogenic anti-Xa is the therapeutic range.

Answer to Question 2

ANS: A
Aspirin, as well as other antiplatelet drugs, have been shown to be effective for prevention of arterial thrombosis, especially myocardial infarction, stroke, and peripheral artery occlusion. This therapy is not monitored. However, some individuals are resistant to aspirin therapy, and thromboxane B2 tests are available, although they are not easily performed or widely available.