A 45-year-old laboratory volunteer is used as the normal control for a platelet aggregation run. He has had a tonsillectomy and two tooth extractions without excess bleeding and takes no medicines. His platelet count is 245 × 10^3/µL [245 × 10^9/L], with platelets of normal size. Light transmission aggregation of his platelet-rich plasma shows no response at all, not even a primary wave, to ADP, epinephrine, collagen and arachidonic acid, while ristocetin gives a normal response. On checking, the technologist finds that the platelet-rich plasma was prepared from a tube with a lavender stopper. The best conclusion is:

Invalid result; recollect in citrate

Undiagnosed Glanzmann thrombasthenia

Aspirin-like cyclooxygenase defect

Undiagnosed Bernard-Soulier syndrome

Why is clot retraction absent in Glanzmann thrombasthenia?

GPIIb/IIIa cannot link fibrin to platelet actin

Platelets cannot synthesize thromboxane A2

Dense granules lack ADP and serotonin

Platelets: qualitative disorders (vWD, Bernard-Soulier, Glanzmann)

10 ASCP MLS practice questions on Platelets: qualitative disorders (vWD, Bernard-Soulier, Glanzmann), part of Hematology. The first 10 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A 45-year-old laboratory volunteer is used as the normal control for a platelet aggregation run. He has had a tonsillectomy and two tooth extractions without excess bleeding and takes no medicines. His platelet count is 245 × 10^3/µL [245 × 10^9/L], with platelets of normal size. Light transmission aggregation of his platelet-rich plasma shows no response at all, not even a primary wave, to ADP, epinephrine, collagen and arachidonic acid, while ristocetin gives a normal response. On checking, the technologist finds that the platelet-rich plasma was prepared from a tube with a lavender stopper. The best conclusion is:
1. AInvalid result; recollect in citrate
2. BUndiagnosed Glanzmann thrombasthenia
3. CAspirin-like cyclooxygenase defect
4. DUndiagnosed Bernard-Soulier syndrome
Show answerHide answer
Answer: A · Invalid result; recollect in citrate
Absent aggregation to every agonist with a normal ristocetin response is the Glanzmann pattern, but it does not fit a man who has had surgery and dental extractions without bleeding. A lavender-stopper tube contains EDTA, which chelates calcium; GPIIb/IIIa needs calcium to bind fibrinogen, so no agonist can cause aggregation. Ristocetin agglutination, in which von Willebrand factor links platelets through GPIb, does not depend on calcium, so it stays normal. Aggregation studies need 3.2% sodium citrate blood kept at room temperature and tested within about 4 hours. An aspirin-like defect would leave primary waves with ADP and epinephrine, and Bernard-Soulier syndrome shows an absent ristocetin response with giant platelets.
- B: Glanzmann thrombasthenia bleeds from infancy; this pattern comes from EDTA, which blocks GPIIb/IIIa.
- C: A cyclooxygenase defect leaves primary waves with ADP and epinephrine.
- D: Bernard-Soulier syndrome has giant platelets and no ristocetin response.
Question 2 · Easy
Bernard-Soulier syndrome is caused by a deficiency of platelet glycoprotein:
1. AVI
2. BIb-IX-V
3. CIIb/IIIa
4. DIa/IIa
Show answerHide answer
Answer: B · Ib-IX-V
Bernard-Soulier syndrome is an autosomal recessive lack or defect of the GPIb-IX-V complex, the platelet receptor for von Willebrand factor. Without it, platelets cannot stick to vWF on exposed subendothelium, so ristocetin gives no response. Platelets are giant and the count is often low. Flow cytometry shows reduced CD42b (GPIbα).
- A: GPVI is a collagen receptor; its rare deficiency affects collagen responses only.
- C: GPIIb/IIIa is missing in Glanzmann thrombasthenia.
- D: GPIa/IIa (integrin α2β1) is a collagen receptor, not the vWF receptor.
Question 3 · Hard
An adult with lifelong bruising has platelets of 62 × 10^3/µL (62 × 10^9/L), and many platelets on the film are as large as red cells. Aggregation is normal with ADP, collagen, epinephrine and arachidonic acid. There is no response to ristocetin, even after adding normal plasma. vWF antigen and activity are normal. The most likely diagnosis is:
1. AGlanzmann thrombasthenia
2. BMYH9-related disorder
3. CType 3 von Willebrand disease
4. DBernard-Soulier syndrome
Show answerHide answer
Answer: D · Bernard-Soulier syndrome
Giant platelets, a low count and an isolated absent ristocetin response that normal plasma does not correct point to Bernard-Soulier syndrome. The missing GPIb-IX-V complex is the vWF receptor, so adding vWF in normal plasma cannot help. Normal vWF levels exclude von Willebrand disease. Analyzers may count giant platelets as red cells, so the film estimate is the better check.
- A: Glanzmann platelets are normal in size and fail with all agonists except ristocetin.
- B: MYH9 disorders have giant platelets but a normal ristocetin response, with Döhle-like inclusions.
- C: Type 3 vWD has very low vWF levels, and normal plasma corrects the ristocetin response.
Question 4 · Medium
Ristocetin-induced aggregation of a patient's platelet-rich plasma is markedly reduced. Adding normal platelet-poor plasma restores the response. This points to:
1. ABernard-Soulier syndrome
2. BAspirin effect
3. CVon Willebrand disease
4. DGlanzmann thrombasthenia
Show answerHide answer
Answer: C · Von Willebrand disease
Ristocetin makes von Willebrand factor bind platelet GPIb, which clumps the platelets. A poor response can come from missing or abnormal vWF in the plasma or from missing GPIb on the platelets. Normal plasma supplies vWF, so it corrects von Willebrand disease but not Bernard-Soulier syndrome, where the defect is on the platelets. vWF antigen, activity and multimer studies then classify the type.
- A: In Bernard-Soulier syndrome the receptor is missing, so normal plasma does not correct the response.
- B: Aspirin does not affect the ristocetin response.
- D: Glanzmann platelets respond normally to ristocetin.
Question 5 · Medium
Why is clot retraction absent in Glanzmann thrombasthenia?
1. APlatelets cannot synthesize thromboxane A2
2. BGPIIb/IIIa cannot link fibrin to platelet actin
3. CDense granules lack ADP and serotonin
4. DPlatelets cannot adhere to vWF
Show answerHide answer
Answer: B · GPIIb/IIIa cannot link fibrin to platelet actin
Clot retraction happens when platelet actin and myosin contract and pull on fibrin strands held by GPIIb/IIIa. Without functional GPIIb/IIIa, the platelets cannot grip the fibrin, so the clot stays loose and large. Adhesion to vWF through GPIb, thromboxane synthesis and granule contents are all normal in Glanzmann thrombasthenia. Absent clot retraction was a classic screening clue before flow cytometry was widely available.
- A: Lack of thromboxane is the aspirin effect, which does not stop clot retraction.
- C: Empty dense granules describe storage pool disease, not Glanzmann thrombasthenia.
- D: Failure to adhere to vWF is the Bernard-Soulier defect, which leaves clot retraction normal.
Question 6 · Medium
Platelet aggregation results: arachidonic acid, absent; ADP and epinephrine, primary wave only; collagen, reduced; ristocetin, normal. What is the most likely cause?
1. ABernard-Soulier syndrome
2. BGlanzmann thrombasthenia
3. CVon Willebrand disease
4. DRecent aspirin use
Answer and explanation in LearnFree account
Question 7 · Hard
Platelet aggregation results: ADP, markedly reduced at all concentrations; arachidonic acid, normal; collagen, mildly reduced; ristocetin, normal. Which drug is most likely responsible?
1. AClopidogrel
2. BWarfarin
3. CAspirin
4. DEptifibatide
Answer and explanation in LearnFree account
Question 8 · Easy
What are the platelet count and platelet size typically like in Glanzmann thrombasthenia?
1. AHigh count with large platelets
2. BLow count with giant platelets
3. CLow count with small platelets
4. DNormal count and normal size
Answer and explanation in LearnFree account
Question 9 · Hard
A 6-year-old child of first-cousin parents has had nosebleeds since infancy. Platelet count and size are normal. Aggregation is absent with ADP, collagen, epinephrine and arachidonic acid but normal with ristocetin. Which result would confirm the diagnosis?
1. ALow CD41 and CD61 on platelets
2. BLow CD42b and CD42a on platelets
3. CLow vWF activity and antigen
4. DAbsent dense granules on EM
Answer and explanation in LearnFree account
Question 10 · Hard
A patient's platelet-rich plasma aggregates with low-dose ristocetin (0.5 mg/mL). The patient's plasma mixed with washed normal platelets also aggregates with low-dose ristocetin, but the patient's washed platelets in normal plasma do not. The abnormality is in the:
1. ARistocetin reagent concentration
2. BPatient's GPIIb/IIIa receptor
3. CPatient's GPIbα (platelet-type vWD)
4. DPatient's vWF (type 2B vWD)
Answer and explanation in LearnFree account

Platelets: qualitative disorders (vWD, Bernard-Soulier, Glanzmann)

Bernard-Soulier syndrome is caused by a deficiency of platelet glycoprotein:

Ristocetin-induced aggregation of a patient's platelet-rich plasma is markedly reduced. Adding normal platelet-poor plasma restores the response. This points to:

Why is clot retraction absent in Glanzmann thrombasthenia?

Platelet aggregation results: arachidonic acid, absent; ADP and epinephrine, primary wave only; collagen, reduced; ristocetin, normal. What is the most likely cause?

Platelet aggregation results: ADP, markedly reduced at all concentrations; arachidonic acid, normal; collagen, mildly reduced; ristocetin, normal. Which drug is most likely responsible?

What are the platelet count and platelet size typically like in Glanzmann thrombasthenia?

A 6-year-old child of first-cousin parents has had nosebleeds since infancy. Platelet count and size are normal. Aggregation is absent with ADP, collagen, epinephrine and arachidonic acid but normal with ristocetin. Which result would confirm the diagnosis?

A patient's platelet-rich plasma aggregates with low-dose ristocetin (0.5 mg/mL). The patient's plasma mixed with washed normal platelets also aggregates with low-dose ristocetin, but the patient's washed platelets in normal plasma do not. The abnormality is in the: