Canis ISSN: 2398-2942

Hematology: activated partial thromboplastin time

Synonym(s): APTT, PTT, Partial thromboplastin time, Kaolin-cephalin clotting time

Contributor(s): Kathleen P Freeman

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).

Sampling

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Tests

Methodologies

  • Citrated plasma is incubated with kaolin and cephaloplastins.
  • Calcium ions are added.
  • Time taken for fibrin to form after addition of calcium is measured.

Availability

  • Most clinical pathology laboratories offer a basic hemostatic profile.

Validity

Sensitivity

  • More sensitive than activated clotting time (ACT) Hematology: activated clotting time.
  • Relatively insensitive since activity of clotting factor must be <30% to result in abnormal elevation.

Specificity

  • Does not require presence of platelets.
  • Useful for evaluating secondary haemostasis in dogs with severe thrombocytopenia Hematology: platelet count.

Technique (intrinsic) limitations

  • Some methods/instruments used for human testing are not suitable for canine specimens. The instrument and method should be validated for canine specimens.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • 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.


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