Overview
- Evaluating intrinsic system plus common pathway helps determine whether bleeding is due to defect in coagulation (secondary hemostasis) or other causes (trauma, ulceration, neoplasia, von Willebrand's disease).
Uses
Alone
- Evaluation of intrinsic clotting system and common pathway.
In combination
- With one-stage prothrombin time (OSPT)
: evaluation of clotting system.
Other points
- Deficiencies of factors VIII, IX, X, XI, XII, II, or I and prekallikrein can also be evaluated with whole blood clotting time or activated clotting time , but levels of clotting factor must be less than 5% normal.
Result data
Normal (reference) values
- Submission of a control specimen from a normal dog may be helpful in controlling for pre-analytical factors.
- 10-15 seconds, or >1.25X pooled canine plasma control specimen.
Abnormal values
- >15 seconds suspect hemostasis disorder.
- >20 seconds → prolonged significantly, coagulation factor abnormality likely present.
- Deficiencies (<30%) of factors VIII, IX, X, XI, XII, II, or I. Prekallikrein deficiency (rare) may also cause prolonged APT.
- Fibrinogen (factor I) deficiency .
- Anticoagulant inhibition, eg heparin.
- DIC, in combination with other abnomalities.
- Liver disease.
- Rodenticide toxicity.
- von Willebrand's disease (vWD) may result in slight prolongation of APT.
Errors and Artifacts
- Test inhibited by heparin.
Sources
Publications
Refereed papers
- Couto C J (1999) Clinical approach to the bleeding dog or cat. Vet Med May , 450-459.
- Sheafer S E & Couto C J (1999) Clinical approach to a dog with anticoagulant rodenticide poisoning. Vet Med May , 466-471.
Other sources of information
- Kaneko J J, Harvey J W & Brass M L (eds) (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Boston: Academic Press.
- Jain N C (1993) Essentials of Veterinary Hematology. Philadelphia: Lea and Febiger.
