You review a 40 year old male with chest pain and shortness of breath. He had been admitted with a deep vein thrombosis in his right leg. His coagulation profile is shown below.
INR |
1 |
(0.9 TO 1.2) |
APTT |
61 seconds |
(24 to 39 sec) |
PT |
11.5 seconds |
(10.5 to 13.5 sec) |
A. List 5 causes of the abnormality in the coagulation profile
B. List 5 tests that could differentiate the cause of this abnormality
A. List 5 causes of the abnormality in the coagulation profile
Heparin
Lupus inhibitor
Haemophilia A & B
Factor xii deficiency
Factor xi deficiency
Von Willebrands disease
Artefactual (incorrect amount of blood in the tube.)
B. List 5 tests that could differentiate the cause of this abnormality
Repeat test
Heparinase assay or antibodies
Mixing test
Thrombin time and reptilase time
Factor assay
Anti-cardiolipin antibody
This is another "What is the cause of an isolated APTT elevation" question.
The abnormal coagulation studies page deals with this in greater detail.
The approach to a patient wth abnormal coags can be summarised in the form of a table:
Normal PT | Raised PT | |
Normal APTT |
|
Extrinsic pathway failure
|
Raised APTT |
Intrinsic pathway failureFactor deficiency or anticoagulant factor? This is answered by mixing studies.
|
Intrinsic and extrinsic pathway failure
|
In brief, the raised APPT could be caused by either an anticoagulant factor, or by a deficiency of the factors involved in the intrinsic or final common pathway.
Thus, it could be any of the following:
The tests one would wish to perform?
In their answer, the college also intelligently suggest that you repeat the APTT, as it could all be an artifact of sampling.
Hunt, Beverley J. "Bleeding and coagulopathies in critical care." New England Journal of Medicine 370.9 (2014): 847-859.