Hematology: platelet count

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Sections available in full article Uses, Sampling, Source of test material, Quantity of test material, Sample collection technique, Quality control, Test (s), Methodologies, Availability, Validity, Result data, Normal (reference) values, Abnormal values, Errors and Artifacts, Sources, Publications, Vetstream contributor(s),
Contributors Dr Kathleen P Freeman DVM MS PhD MRCVS
Synonyms Thrombocyte

Uses

Alone

  • Assessment of platelet numbers.

In combination

  • As part of routine hematological screen.
  • In diagnosis of immune-mediated thrombocytopenia Immune-mediated thrombocytopenia.
  • With activated partial thromboplastin time (APTT), prothrombin time (PT) + fibrin degradation product (FDP) Fibrin degradation products in diagnosis of disseminated intravascular coagulation (DIC) Disseminated intravascular coagulation.
Other Points
  • Kidney involved in manufacture of thrombopoietin/thrombocytosis stimulating factor (TSF).
  • Platelets live longer than WBCs. Therefore, in bone marrow suppression leukopenia is usually seen before thrombocytopenia.
  • Rarely, thrombocytosis can be seen in the following non-pathological conditions: excitement/exercise (splenic contraction), following splenectomy (loss of storage pool) and during late pregnancy.

Result data

Normal (reference) values

  • 200-500 x 10*9/l.
  • <100 x 10*9/l significant.
  • Spontaneous hemorrhage is likely to occur with platelet counts <30-50 x 10*9/l.

Abnormal values



Increased [platelet] (thrombocytosis)
  • Associated with iron deficiency anemia Anemia: non-regenerative.
  • Drug-induced, eg vincristine Vincristine , glucocorticoids Hydrocortisone , epinephrine Epinephrine.
  • Chronic infection/inflammation, eg bronchitis (rare) Chronic bronchitis.
  • Persistent or chronic hemorrhage.
  • Myeloproliferative disorders Lymphoproliferative disease , eg primary polycythemia Hematology: complete blood count (CBC) and basophilic leukemia Leukemia.
Decreased [platelet] (thrombocytopenia)
  • Immune-mediated thrombocytopenia (IMTP) Immune-mediated thrombocytopenia.
  • Aplastic anemia - many possible causes including estrogens (thrombocytosis initially), phenylbutazone Phenylbutazone , thiazide diuretics Chlorothiazide , toxins and chemotherapeutic drugs Chemotherapy: general principles.
  • Myeloproliferative and lymphoproliferative disorders Lymphoproliferative disease.
  • Myelophthisic disease.
  • ??'Rebound' thrombocytopenia (following blood transfusion Anemia: transfusion indications ).
  • Infection, eg canine parvovirus Parvovirus disease associated with CPV-2 , infectious canine hepatitis Canine adenovirus type 1 disease , leptospirosis Leptospirosis , salmonellosis Salmonellosis , histoplasmosis Histoplasma capsulatum , bacteremia and systemic mycosis.
  • Disseminated intravascular coagulation (DIC) Disseminated intravascular coagulation.
  • Splenomegaly/hypersplenism.
  • Anaphylaxis Anaphylaxis, urticaria and angioedema.
  • Other immune-mediated disorders, eg systemic lupus erythematosus (SLE) Systemic lupus erythematosus.
  • Massive hemorrhage.

Errors and Artifacts



False decrease
  • Platelet aggregation (clumping) occurs rapidly and produces false low values.
  • Clotting.
  • Platelet clumping:
    • Exposure to EDTA.
    • Prolonged storage.

Sources

Publications

Refereed papers

  • Couto C G (1999) Managing thrombocytopenia in dogs and cats. Vet Med 5 , 460-465.

Other sources of information

  • Cowell R J, Tyler R D & Meinkoth J H (1999) Diagnostic Cytology and Hematology of the Dog and Cat. 2nd edn. St Louis: Mosby.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine Clinical Pathology. 3rd edn. Ames, Iowa: Iowa University Press.
  • Jain N C (1993) Essentials of Veterinary Hematology. Philadelphia: Lea & Febiger.

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