Author Question: A patient sample has normal platelet aggregation patterns for all agonists except that no reaction ... (Read 75 times)

dakota nelson · **on:** Jun 25, 2018

A patient sample has normal platelet aggregation patterns for all agonists except that no reaction occurs with ristocetin. Ristocetin agglutination is not corrected with exogenous VWF. What condition is most likely?

a. VWD
b. Storage pool disorder
c. Bernard-Soulier syndrome
d. Aspirin use

Question 2

Which of the following is an acceptable sample for testing on a photo-optical clot-detecting instrument?

a. Lipemic plasma
b. Hemolyzed plasma
c. Serum
d. Plasma collected using a 9:1 ratio of whole blood to 3.2 sodium citrate

sarajane1989 · **Reply #1 on:** Jun 25, 2018

Answer to Question 1

ANS: C
Platelets from patients with Bernard-Soulier syndrome do not agglutinate with ristocetin, and it is not corrected when exogenous VWF is added. Their platelets have an intrinsic membrane defect, a deficiency of the GP1b or IX portion of the GP1b/V/IX receptor. This is in contrast to platelets from patients with VWD; they also do not agglutinate with ristocetin, but agglutination is corrected when exogenous VWF is added. Platelets from patients with storage pool disorder or those taking aspirin agglutinate normally with ristocetin.

Answer to Question 2

ANS: D
Plasma should be collected at a 9:1 ratio of blood to anticoagulant (3.2 sodium citrate). Lipemia and hemolysis are possible interfering substances when using an instrument that uses the photo-optical principle for end-point detection. Serum cannot be used for coagulation testing because the sample has already clotted, with resultant loss of several coagulation proteins.