Practical-Haemostasis.com

A Practical Guide to Laboratory Haemostasis

 

Data Interpretation: Platelet Function Testing



Introduction

The following questions will allow you to work through a number of scenarios that relate to platelet function testing.

Question 1
Study the following aggregation traces and establish the diagnosis.
Remember there may be more than one possible answer for each set of aggregation traces.

If you click HERE this will load an enlarged version of these aggregation traces in a new window.



1. What are the possible diagnoses that would explain these abnormalities?
2. What additional tests might you request?


Question 2
Study the following aggregation traces and establish the diagnosis.
Remember there may be more than one possible answer for each set of aggregation traces.

If you click HERE this will load an enlarged version of these aggregation traces in a new window.




1. What are the possible diagnoses that would explain these abnormalities?

Click here for Part 2


1. You suspect a diagnosis of BSS or VWD or even platelet-type VWD. How would you distinguish between these three possibilities?


Question 3
Study the following aggregation traces and establish the diagnosis.
Remember there may be more than one possible answer for each set of aggregation traces.

If you click HERE this will load an enlarged version of these aggregation traces in a new window.



1. What are the possible diagnoses that would explain these abnormalities?

Click here for Part 2


You suspect a diagnosis of either Storage Pool Disorder or an abnormality of the platelet nucleotide release. What additional test will you request?


Question 4
Using the data shown below for a VWF:RCo assay using platelets - calculate the VWF:RCo activity in the two plasma samples 1 and 2 [the two samples are shown at the bottom].

1. Assume the reference plasma has a VWF:RCo of 100%.
2. Remember to plot your slopes on double log paper with the dilutions on the X-axis and the slopes on the Y axis.


 

If you click HERE this will load an enlarged version of this graph in a new window.


Question 5

These traces are from a patient with suspected Von Willebrand Disease. What do they show and what is the diagnosis?

Figure 1: Patient Plasma + Control Platelets


Figure 2: Patient Platelets + Control Plasma


Click here for Part 2


What is the underlying molecular abnormality in this disorder?


Question 6
Study the following aggregation traces and establish the diagnosis.
Remember there may be more than one possible answer for each set of aggregation traces.




Click here for Part 2


These aggregation traces were obtained from a 12-year-old male referred for surgical correction of a complex congenital heart problem. He gave a history of bleeding after dental surgery. There was no family history of note and his parents were not related. His platelet count was 107 x 109/L and the MPV was 11.6fL. A blood film showed the presence of giant platelets.

What additional diagnosis must you consider?


Question 7

These aggregation traces were obtained from a 23-year-old woman referred for investigation of life-long menorrhagia and prolonged bleeding after dental extraction.

Test Patient Reference Range
PT 11.2s 11.5-13.5s
APTT 34s 28-34.5s
FVIII:C 59 IU/dL 50-150 IU/dL
VWF:Ag
VWF:RCo
56 IU/dL
24 IU/dL
50-150 IU/dL
50-150 IU/dL
Platelets 79 x 109/L 150-400 x 109/L



1. What diagnoses would you consider?
2. What the treatment options for this woman?


Question 8
These aggregation traces were obtained from a 33-year-old woman referred for investigation of life-long menorrhagia and prolonged bleeding after dental surgery. There was a family history suggestive of a bleeding disorder but no conclusion had ever been reached.

The referring hospital had performed a PFA100 and the closure time using both ADP/Collagen and ADP/Adrenaline were prolonged.


1. What the major abnormalities?
2. What is the most likely diagnosis?

Click here for Part 2


You suspect either Storage Pool Disorder or a Primary Secretion Defect - how will you distinguish between the two?


Question 9
A 67-year-old man has coronary angiography and develops a large haematoma at the catheter insertion site. He has the following tests performed prior to stenting.

What do these tests show?
What are possible explanations for these findings?




Click here for Part 2


1. What advice would you give to the cardiologists?


Question 10
These aggregation traces were obtained from an 18-year-old student under investigation for easy bruising. She had a prolonged closure time of >300s with PFA100 [Collagen-Adrenaline cartridge].


1. What possible diagnoses would you consider?

2. To confuse you - the control and patient traces have been reversed and the control is in red and the patient in black.


Question 11
A 25-year-old Indian woman is investigated for recurrent miscarriages and menorrhagia

Test Patient Reference Range
PT >120s 11.5 -13.2s
APTT >120s 26-32s
Fibrinogen (Clauss) Not requested 2-4g/L
Bleeding Time >20 minutes <10 minutes
PFA100
  Collagen-ADP
  Collagen-Adrenaline

>300s
>300s

<110s
<112s

Comment upon the results of these tests.
What would you do next?

Click here for Part 2


Shown below are the results of limited aggregation studies.



1. What is the most likely diagnosis?
2. What additional tests would you request?
3. What are the treatment options for this woman in pregnancy?


Question 12
A 43-year-old male with no past medical history of note, is admitted to hospital with a history of recent onset of recurrent and prolonged epistaxes. The results of initial investigations are shown below:

1. Comment upon the results of these investigations.
2. What tests would you request next?

Test Patient Reference Range
Hb 8.9 g/dL 13.5-16.5g/dL
Platelets 110 x 109/L 150 - 400 x 109/L
PT 13s 11.5 -13.2s
APTT 34s 26-32s
Fibrinogen 3.4 g/L 2-4 g/L
Bleeding Time >30 minutes < 10 minutes

Click here for Part 2


You suspect an acquired platelet disorder due to the recent onset of symptoms and the prolonged bleeding time; You request platelet aggregation studies. The results of one of these tests using Ristocetin [1.5mg/ml] is shown below.
1. Comment upon the results of this.
2. What you do next?


 

Click here for Part 3

You consider the possibility of an acquired platelet disorder further - look at the following traces.
[The first aggregation trace from Part 2 is shown again to help you. An IgG fraction was prepared from the patients plasma and from a control plasma.]

What does this suggest?




Question 13
A 23-year-old man is investigated for the possibility of an inherited platelet disorder. His full blood count is normal apart from a platelet count of 55 x 109/L. The MPV is 11.2fL and the blood film shows the presence of giant platelets.

Shown below are the results of flow analysis using 3 separate monoclonal antibodies [CD40, CD42b and CD610 - and the results are expressed as median fluorescence intensity.

Sample
Platelet Count [ x 109/L]
MPV [fL]
CD41
CD61
CD42b
Control
268
8.6
4.87
28.7
6.23
Patient
55
11.2
19.9
55.2
2.39
1. How would you explain these findings?
2. What is a possible diagnosis and how would you confirm this?


Question 14
A 32-year-old woman is admitted through the Emergency Department with a short history of easy bruising. She is slightly confused.

Test Patient Reference Range
PT 12.5s 11.5 -13.2s
APTT 33s 26-32s
Fibrinogen (Clauss) 1.9 g/L 2-4 g/L
Thrombin Time 14.5s 12.5-13.9s

1. What additional tests would you request?

Click here for Part 2


1. You request the following:

Test Patient Reference Range
Platelet count 34 x 109/L 150 - 400 x 109/L
Blood Film Marked red cell fragmentation noted  
LDH 2400 U/L <450 U/L
Troponin T 0.9  μg/L 0–0.01 μg/L

What is the most likely diagnosis?
How will you manager this patient?
Are there any other tests you might request?

 

Click here for Part 3


1. You request an HIV screen which is positive. Will this affect your management?
2. What is the significance of the raised Troponin T and LDH?


Question 15
A 28-year-old male is investigated for the possibility of an inherited bleeding disorder. Platelet aggregation testing was not available but the results of platelet membrane glycoprotein analysis by flow are show below.

Comments upon the results of these tests.
Do these tests suggest a diagnosis?




FS: Forward scatter
SS: Side scatter

In this analysis three antibodies [CD41, CD61 and CD42b] directed against specific platelet membrane glycoproteins were used:

Antibody Specificity
CD41 CD41 recognises the platelet membrane glycoprotein GpIIb (the integrin alpha IIb chain) which is non-covalently associated with GpIIIa (the integrin beta 3 chain) to form the GpIIb/IIIa complex.
CD61 CD61 recognises the platelet membrane glycoprotein GpIIIa (the integrin beta 3 chain).
CD42b CD42b reacts with GpIb on megakaryocytes and platelets.  CD42b also inhibits ristocetin-dependent binding of Von Willebrand Factor to platelets and ristocetin-induced platelet agglutination.



Question 16
A 4-year-old girl is investigated for persistent epistaxes.

Test Patient Reference Range
PT 12.8s 11.5 -13.2s
APTT 23s 26-32s
Fibrinogen (Clauss) 2.9g/L 2-4 g/L
Platelets 45 x 109/L 100-400 x 109/L

1. What tests would you request?

Click here for Part 2


1. You request a blood film and an MPV. The MPV is 12.3fL and the blood film is shown below:


What is the most likely diagnosis?
Are there any other tests you might request?


Click HERE for Part 3
The results of platelet aggregation tests are shown below:



Comment upon the results of these investigations?
What additional tests might you request?
What is the diagnosis?


Click HERE to return to the top of the page.

Click HERE for the Answers

Try to avoid looking at the answers until you have worked through the questions.