Question 12.3

Angoff score
6.36
Highest mark
9.5
Other SAQs in this topic:
Other SAQs in this paper:

A 52-year-old patient presents with bruising and a retroperitoneal haematoma five weeks after starting warfarin for a proximal deep vein thrombosis (DVT) with a target international normalised ratio (INR) of 2.5.

The following investigations were obtained:
 

Parameter

Patient Value     

Adult Normal Range

Haemoglobin

122 g/L*

135-180

White Cell Count

10.1 x 109/L

4.0-11.0

Platelets

298 x 109/L

150-400

Prothrombin time

29.3 sec*

12.0-16.5

International normalised ratio (INR)

2.3*

0.9-1.3

Activated partial thromboplastin time (APTT)       

117.0 sec*

27.0-38.5

Fibrinogen

3.9 g/L

2.0-4.0


12.3.1    List the likely underlying cause for this coagulation profile.    (2 marks)
12.3.2    List two confirmatory tests.    (2 marks)
 

[Click here to toggle visibility of the answers]

College Answer

Syllabus topic/section:
2.1.21 Applied Pharmacology in Intensive Care.
Aim:
To allow the candidate to demonstrate competency in data interpretation.
Discussion:
Candidates generally did extremely well in this repeat data question. Candidates are reminded that if the question asks you to list 6 causes there are only marks for 6 answers. If 8 are written the top 6 will be assessed and the bottom 2 causes will not be marked.

Discussion

This is a repeat of Question 25.3 from the second paper of 2020.

The abnormalities are:

  • A slightly lower haemoglobin then you would expect from a normal range (though, a slightly higher haemoglobin than what you would expect from a woman with a retroperitoneal haematoma)
  • A raised prothrombin time
  • An increased INR, though totally within the therapeutic range for her DVT
  • A wildly elevated APTT

So: the extrinsic pathway is working normally (for a warfarinised lady), but the intrinsic pathway is broken. Why would that be? Naturally, you'd classify these abnormalities into two broad groups:

  • Factor deficiency
  • Anticoagulant element

Factor deficiency seems less plausible given the history. So: what anticoagulant factors can there be? Or rather; what anticoagulant factor can you think of w, which might give rise to a bleeding propensity but at the same time predispose somebody to having clots? Antiphospholipid syndrome comes to mind. 

b) 

You would want to order:

  • Antiphospholipid antibodies
  • Mixing studies

Theoretically you could also order thrombin time and reptilase time, as antiphospholipid syndrome would have a normal; TT and RT.

References

Kamal, Arif H., Ayalew Tefferi, and Rajiv K. Pruthi. "How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults." Mayo Clinic Proceedings. Vol. 82. No. 7. Elsevier, 2007.

Hunt, Beverley J. "Bleeding and coagulopathies in critical care." New England Journal of Medicine 370.9 (2014): 847-859.

Miyakis, Spyridon, et al. "International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS)." Journal of Thrombosis and Haemostasis 4.2 (2006): 295-306.

[Submit a comment or correction]