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A Practical Guide to Laboratory Haemostasis

 

Data Interpretation: Thrombophilia Assays



Introduction

This section covers thrombophilia assays and thrombophilia testing but strays into other areas and so is not specific to these tests. The reference section will provide information that you may find of help.

Question 1

A 34-year-old woman [II:1 in the pedigree below] is 12 weeks pregnant. She had a brother [II:3] who died from purpura fulminans shortly after birth and subsequent investigations showed that he had homozygous Protein C deficiency with a Protein C activity of <1 IU/dL.

1. What is the risk that her baby [III:1] will be born with homozygous Protein C deficiency. The mother and her partner are unrelated and the prevalence of heterozygous protein C deficiency in the population is 1/500 [for this example].
2. What is the risk that her baby will be born with homozygous Protein C deficiency if the partner is found to have low Protein C activity levels consistent with Protein C deficiency.

The pedigree is shown below to help you:
[Squares - males; circles - females; solid square - affected male;

                   


Question 2

A 65-year-old man is admitted for a bioprosthetic aortic valve replacement [AVR]. He comes off cardio-pulmonary bypass without problems but 3 days later develops an iliofemoral DVT. He is treated with unfractionated heparin but his platelet count begins to fall and 5 days into treatment he has a platelet count of 28 x 109/L.

What tests are you going to request and how will you manage this patient?

Test Patient Reference Range
INR 1.2 1.0
APTT 65s 28-34s
Fibrinogen (Clauss) 3.4 g/L 2-4 g/L
Thrombin Time >60s 11.5-13s
Platelet Count 28 x 109/L 150-400 x 109/L


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1. You make a diagnosis of HIT and treat him with fondaparinux.

Unfortunately he needs develops a paraprosthetic valvular leak and 6 months after his original AVR he is scheduled for a replacement. You are asked to advise on how to manage him on bypass and in particular can he receive unfractionated heparin. What would you advise?


Question 3

A 43-year-old man has a history of Heparin-Induced Thrombocytopaenia [Type II HIT] and is admitted with an extensive left proximal DVT.
1. How are are you going to manage this patient?
2. Depending on your choice of anticoagulant what tests will you employ to monitor this?

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1. You elect to treat him with lepirudin by continuous iv infusion. You monitor his anticoagulation by means of an Ecarin clotting time. 5 days into treatment his requirements for lepirudin begin to decrease. What do you think has happened?


Question 4

A 23-year-old woman is referred to you to discuss a pulmonary embolism she developed following a long-haul flight to the Arctic. The results of her thrombophilia screen [off all anticoagulants] are shown below:

Test Patient Reference Range
Antithrombin activity 92 U/dL >78 U/dL
Protein C activity 34 U/dL >63 U/dL
Protein S activity 35 U/dL >60 U/dL
Lupus anticoagulant Not detected  
IgG Anti-β2 GP1 antibody 2.9 units/ml 1-6 units/ml
1. What is the diagnosis?
2. Are there any other tests you would request and if so why?

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1. Investigations show that she is homozygous for the Factor Leiden mutation - is this significant in the terms of other aspects of the thrombophilia screen?

2. What additional tests might help you in this situation?


Question 5

An 8-year-old boy with sickle cell disease [Hb SS] develops a portal vein thrombosis. He has a thrombophilia screen performed which shows:

Test Patient Reference Range
Antithrombin activity 104 U/dL >78 U/dL
Protein C activity 35 U/dL >63 U/dL
Protein S activity 42 U/dL >60 U/dL
Free Protein S Ag 46 U/dL >61 U/dL
PT 12s 11.5 - 13.5s

1. Comment upon the results of these tests.
2. Do they provide an explanation for his portal vein thrombosis?


Question 6

A 4-year-old boy is admitted to hospital with what appears to be purpura fulminans. He has a thrombophilia screen performed which shows:
The only other history of note is that he had recently had a vesicular rash.

Test Patient Reference Range
Antithrombin activity 109 U/dL >78 U/dL
Protein C activity 82 U/dL >63 U/dL
Protein S activity 2 U/dL >60 U/dL
Free Protein S Ag 3 U/dL >61 U/dL
APCr 2.3 >2.20
Prothrombin G20210A G/G [Wild Type sequence]  

1. What is the diagnosis?
2. How will you manage this patient?


Question 7

A 45-year-old man develops an apparent spontaneous proximal DVT. He has some baseline pre-anticoagulant investigations performed:

Test Patient Reference Range
PT 23s 11.5-13.5s
APTT 72s 28-34s
Fibrinogen (Clauss) 3.9g/L 2-4g/L
Platelet count 189 x 109/L 150-400 x 109/L

1. What additional tests might you request?

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1. The APTT does not not correct in a mix with normal plasma.
2. What will you request next?

 

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1. You request a screen for lupus anticoagulant, the results of which are shown below:

Test Patient Reference Range
Silica Clotting Time [SCT] 2.97 <1.54
SCT + PL 54% <15%
Dilute Russell Viper Venom Time [DRVVT] 2.40 <1.20
DRVVT + PL 54.1% <15%

1. What is the diagnosis?
2. What else will you suggest?
3. What anticoagulants would you suggest for this patient?
4. How will you monitor this patient if he requires long-term anticoagulation with a vitamin K antagonist e.g. warfarin


Question 8

Comment upon the results of the following blood tests.
What is the diagnosis?

Test Patient Reference Range
Silica Clotting Time [SCT] 2.77 <1.54
SCT + PL 39% <15%
Dilute Russell Viper Venom Time [DRVVT] 2.01 <1.20
DRVVT + PL 44.1% <15%
APTT 69s 28-34s

1. These results were obtained as part of a pre-operative screen in patient with a suspected colonic malignancy.
2. What advice would you give the surgeons regarding thromboprophylaxis?
3. The surgeons are concerned that this patient will bleed due to the prolonged APTT - what will you tell them.
4. Do patients with a lupus anticoagulant bleed?


Question 9

A 42-year-old woman has a history of 5 consecutive first trimester miscarriages. She has a screen for antiphospholipid antibodies performed and the results are show below:

Test Patient Reference Range
SCT 1.12 <1.54
DRVVT 1.09 <1.20
IgG Anticardiolipin antibody titre 3.2 GPLU/mL 1-12 GPLU/mL

1. Are there any other tests you might request?

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1. You request a screen for Anti-β2 glycoprotein antibodies. The result is 221 units/ml with a reference range of 1-6 units/mL.

2 What is the explanation for these findings and how would you manage a future pregnancy in this lady?


Question 10

A 23-year-old man is admitted with suspected appendicitis. He has a pre-operative screen performed which shows:

Test Patient Reference Range
PT 12s 11.5-13s
APTT >120s 28-34s
Fibrinogen (Clauss) 5.1 g/L 2-4g/L
Thrombin Time 12s 11.8-13.2s

1. What questions might you ask the patient?
2.What tests would you request?

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1. He has no bleeding history despite removal of 4 wisdom teeth 2 years previously.
2. His FXII:C is <1 IU/dL

What advice will you give the surgeons regarding FXII replacement therapy?


Question 11

A 39-year-old barrister is admitted with a proximal DVT. An enthusiastic doctor checks his fasting homocysteine and it is elevated at 220µmol/L [reference range <16 µmol/L].

What are the possible explanations for this?
What questions might you ask this patient?
What tests might you request?
How will you manage this patient?


Question 12

A 2-day-old baby is diagnosed with neonatal purpura fulminans. The results of Protein C assays are shown below:
Comment upon the results of these tests

Test Patient Reference Range
Protein C Antigen 23 U/dL >63 U/dL
Protein C Activity [Chromogenic] 21 U/dL >60 U/dL
Protein S Activity 46 U/dL >61 U/dL


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1. You request family studies and these are shown below:

                  

Test Mother Father Brother Reference Range
Protein C Antigen 47 U/dL 80 U/dL 55 U/dL >63 U/dL
Protein C Activity [Chromogenic] 54 U/dL 79 U/dL 53 U/dL >60 U/dL
Protein S [Free Protein S Antigen] 74 U/dL 79 U/dL 82 U/dL >61 U/dL

Comment upon these tests.
Are there any additional tests you would request?

 

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You request a clotting-based functional Protein C assay - the results of which are shown below:

Test Patient Mother Father Brother Reference Range
Protein C Activity
[Clotting Assay]
<1 U/dL 54 U/dL 51 U/dL 54 U/dL >60 U/dL


                  

Comment upon these tests.
What is the diagnosis and how do you explain the results of all of the tests?


Question 13

Fill in the missing blanks in the following table:

Snake Venom Which Snake Tests used with this venom
Ancrod    
Reptilase    
Botrocetin    
Ristocetin    
Botox    
Protac    
Russell Viper Venom    
Ecarin    
Textarin    


Question 14

A 19-year-old woman develops a cerebral venous sinus thrombosis. investigations show that she is heterozygous for the Prothrombin G20201A mutation. Is this significant and why?|


Question 15

A 23-year-old male is admitted and a diagnosis of TTP is made. Your 'Boss' requests an ADAMTS-13 assay and he quizzes you on the various tests available for measuring ADAMTS-13. What methods currently exist for measuring ADAMTS-13?


Question 16

Look at the following TEG traces and decide what they show:
1.


2.


3.


Question 17

A 46-year-old woman is admitted under the care of the surgeons with a mesenteric vein thrombosis. A thrombophilia screen is requested - she was on no anticoagulants at the time of testing.
Comment upon the results of these tests.

Test Patient Reference Range
PT 13s 11.5-13s
APTT 33s 28-34s
Fibrinogen (Clauss) 4.1 g/l 2-4g/L
Platelets 689 x 109/L 150-400 x 109/L

1. Are there any other tests you might request?

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You request a JAK2 screen which shows her to be heterozygous for the JAK2 V617F mutation. Do you think this provides an explanation for her mesenteric vein thrombosis? If so why?


Question 18

A 59-year-old man is admitted for surgery and found to have a prolonged APTT. Comment upon the results of these investigations and suggest additional tests that you might request

Test Patient Reference Range
PT 13s 11.5-13s
APTT 67s 28-34s
Fibrinogen (Clauss) 4.1 g/l 2-4g/L
Platelets 299 x 109/L 150-400 x 109/L


Click HERE for Part 2

1. You request FVIII, FIX and FIX assays all of which of are normal.. You also took a very careful bleeding history which was negative.
2. You suspect a lupus anticoagulant and request a dRVVT and an SCT.

Show below are the raw data for these tests. What do these suggest and are the results consistent with the presence of a lupus anticoagulant?

Sample SCT Clotting Time [seconds] Ratios
Patient Plasma 339.9 s [Patient Plasma]/[Reference Plasma] =
Reference Control [Normal] Plasma 65.2 s
Patient Plasma + Phospholipid 118.6 s [Patient Plasma + Phospholipid]/Reference Control [Normal] Plasma +  Phospholipid] =
Reference Control [Normal] Plasma +  Phospholipid 62.2 s
% Correction =


Sample dRVVT Clotting Time [seconds] Ratios
Patient Plasma 149.6 s [Patient Plasma]/[Reference Plasma] =
Reference Control [Normal] Plasma 37.3 s
Patient Plasma + Phospholipid 51.6 s [Patient Plasma + Phospholipid]/Reference Control [Normal] Plasma +  Phospholipid] =
Reference Control [Normal] Plasma +  Phospholipid 31.3 s
% Correction =



Question 19

A 56-year-old man has a history of Hodgkin's Lymphoma and is in remission following chemotherapy. He is reviewed in clinic because of sudden onset of bruising, epistaxes and gum bleeding. Examination apart from a number of large bruises was unremarkable. There was no evidence that his Hodgkin's Lymphoma had relapsed.
You request some basic clotting tests, the results of which are shown below:

Test Patient Reference Range
PT 13s 11.5-13s
APTT 32s 28-34s
Fibrinogen (Clauss) 4.1 g/l 2-4g/L
Platelets 299 x 109/L 150-400 x 109/L

Click HERE for Part 2

1. You request a PFA-100 as a screen of platelet function:

PFA-110 Patient Control
ADP-Collagen cartridge > 300s <113s
ADP-Epinephrine cartridge > 300s <112s

What additional tests would you now request?
Are there any questions you might ask the patient?


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1. The patient had not taken any anti-platelet drugs and had not consumed any foodstuffs that would account for the PFA-100 abnormalities.

2. You request formal platelet aggregation studies and these are show below:


Platelet agglutination with Ristocetin
Platelet aggregation with ADP, Collagen and Adrenaline

What do these results suggest?
Are their any additional tests you might request?


Click HERE for Part 4
Shown below are the results of platelet aggregation traces 3 months later [with no treatment].

What do these suggest?

Platelet aggregation with ADP, Collagen and Adrenaline



Question 20

A 34-year-old male presents to your local Emergency Department with a 2-day history of a painful swollen left leg. You suspect a DVT and arrange an urgent ultrasound which confirms an extensive proximal DVT extending into the iliac veins.

Test Patient Reference Range
PT 13s 11.5-13s
APTT 22s 28-34s
Fibrinogen (Clauss) 4.1 g/l 2-4g/L
Platelets 356 x 109/L 150-400 x 109/L

Are there any additional tests you might request or questions you might ask?

 

Click HERE for Part 2

1. There are no obvious risk factors that you can elicit for this individuals to develop a DVT
2. There is no family history of note.

You are surprised by the the short APTT and repeat this and it is again short at 21.5s. What additional tests might you request?

 

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You request Factor VIII, Factor IX, Factor XI and Factor XII assays.
What do you think might be the explanation for this.
How will you manage this patient?


The Factor assays are normal apart from the Factor IX which is 4.56 IU/m [reference 0.5 1.5 IU/mL]



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