Platelets

Question 1

Define hemostasis and primary hemostasis

Answer 1

hemostasis is the stopping of blood to prevent bleeding out
primary hemostasis is the first hemostatic plug made by vWF and platelets

Question 2

Define automated platelet count and estimated platelet count

Answer 2

The automated platelet count is done by the analyzer and can often give spurious results due to platelet clumping so a estimated platelet count must be done using a blood smear and multiplying the amount of platelets per field of view by 15,000

Question 3

Explain how in vitro platelet clumping affects the automated and estimated platelet counts

Answer 3

platelets can clump and skew the automated and estimated platelet counts as multiple cells will be indecipherably counted

always worry about too low numbers as spontaneous hemorrhage can occur

Question 4

Define thrombopathy

Answer 4

abnormal platelet function

Question 5

Define thrombocytopenia

Answer 5

low platelet number

Question 6

Define thrombocytosis

Answer 6

increased number of platelets

Question 7

What are the causes thrombocytopenia?

Answer 7

sequestration - transient splenomegaly

decreased production - bone marrow dx

utilization/consumption - DIC

destruction - immune mediated

Question 8

How would you identify the cause of thrombocytopenia using clinicopathologic data?

Answer 8

1. evaluate blood smear to confirm platelet count, look for infectious agents, send for infectious dx testing like PCR
2. rule out DIC with coagulation test
3. bone marrow evaluation
   - concurrent neutropenia or non-regenerative anemia

Question 9

What is an appropriate amount of platelets?

Answer 9

150,000

Question 10

What are the requirements for hemostasis

Answer 10

intact and healthy vessel
normal platelet numbers
normal platelet function
normal amount and function of clotting factors

Question 11

What number of platelets would you see spontaneous hemorrhage

Answer 11

25,000

Question 12

What are the components involved with primary hemostasis

Answer 12

von Willebrand factor and platelets

Question 13

What are the main causes of thrombopathy

Answer 13

extrinsic
intrinsic which could be hereditary or acquired

Question 14

Explain extrinsic thrombopathy and how you would clinically diagnose it

Answer 14

congenital
most common inherited bleeding disorder
lack of von Willebrand factor which is necessary for platelet adhesion and bridging

Clinically you would see a Normal platelet count and coagulase test
prolonged buccal mucosal bleeding time
low vWF conc.
abnormal closure time
diagnose by DNA testing

Question 15

Explain intrinsic hereditary thrombopathy and how it would clinically be presented and diagnosed

Answer 15

deficiency of a receptor requiring specialized testing - relatively uncommon

patients present similar to extrinsic thrombopathy
bleeding, poor clot formation, normal platelet counts, vWF, and PT/PTT test

Question 16

Explain intrinsic acquired thrombopathy and what it can be caused by

Answer 16

altered metabolism of phospholipid membrane to form thromboxane caused by
drugs like nsaids or steroids

uremia

DIC

liver dx

infections