A 23-year-old previously healthy girl involved in a motor vehicle accident is brought to ICU with multiple rib fractures and laceration of her left forearm. , no acute bleeding, She is haemodynamically stable and there is no evidence of acute bleeding. She has the following coagulation profile:
|
Test |
Result |
Normal range |
|
INR |
1.1 |
0.8-1.2 |
|
Prothrombin time |
11 |
10-15 |
|
APTI |
73 |
35-45 |
|
APTT after protamine |
69 |
35-45 |
|
APTI with 50% normal plasma |
53 |
35-45 |
|
Fibrinogen |
3.4 |
2.5-5 |
a) What is the likely explanation for the APTT result? Give reasons.
b) What further test would you order to confirm the aetiology of the coagulopathy?
c) What vascular complication is this patient at risk of?
d) What drugs might be suitable for DVT prophylaxis in this patient?
College Answer
a) What is the likely explanation for the APTT result? Give reasons.
Antiphospholipid antibody syndrome
Reasons: .
1) Lack of correction with protamine excludes heparin as a cause of prolonged APTT
2) Lack of correction with normal plasma excludes clotting faetor deficiency. Prolongation despite normal plasma suggests circulating anticoagulant. Normal INR and PT and fibrinogen exclude DIC. In a young woman, antiphospholipid antibody syndrome
b) What further test would you order to confirm the aetiology of the coagulopathy?
Lupus anticoagulant
c) What vascular complication is this patient at risk of?
Recurrent DVT/ arterial thrombosis
d) What drugs might be suitable for DVT prophylaxis in this patient?
Short term-aspirin /heparin
Long term-warfarin
Discussion
This is another one of those "why is my APTT so high" questions.
Specifically, this question closely resembles the following questions:
- Question 12.1 from the second paper of 2012
- Question 8.3 from the first paper of 2011
- Question 3.1 from the first paper of 2008
In this case, for some reason somebody gave the trauma patient some protamine. More commonly one would use a heparinase assay or the combination of thrombin time and reptilase time to exclude the effects of heparin, but a "protamine challange" is one way of doing it.
Antiphospholipid syndrome is discussed in greater detail elsewhere.
In brief, the major criteria for diagnosis require one clinical criterion (eg. thrombosis) and one laboratory criterion (eg. a positive anti-β2-glycoprotein-I antibody).
The laboratory tests one could order are as follows:
- Lupus anticoagulant
- Anticardiolipin antibody
- anti-β2-glycoprotein-I antibody
- Antiprothrombin antibody
The antiphospholipid syndrome patient is prone to simultaneously clotting and bleeding.
The specific list of complication is as follows:
- DVT
- PE
- miscarriage
- cerebral sinus thrombosis
- arterial thrombosis
The most recent management guidelines suggest long term warfarin, with a target INR of 2.5.
References
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.
Cervera, Ricard, and Gerard Espinosa. "Update on the catastrophic antiphospholipid syndrome and the “CAPS Registry”." Seminars in thrombosis and hemostasis. Vol. 38. No. 4. 2012.
Keeling, David, et al. "Guidelines on the investigation and management of antiphospholipid syndrome." British journal of haematology 157.1 (2012): 47-58.