Canis ISSN: 2398-2942

Anemia: laboratory investigation

Contributor(s): Prof Bernard Feldman, David Godfrey, Yvonne McGrotty

Introduction

  • Anemia is a sign of disease NOT a diagnosis, that is, not a disease per se.
  • Identification of anemia on a blood screen demands further investigation to characterize the type and establish the etiology of the anemia.
    Follow the diagnostic tree for Hemolytic Anemia  Hemolytic Anemia.

Is the patient anemic?

  • Anemia is an absolute decrease (of more than 2 standard deviations below the normal mean at normal blood volume) in at least one of: PCV may be normal or increased in dehydrated animals with anemia. This is particularly true of Addisonian dogs Hypoadrenocorticism.
  • Once animal is hydrated hematological analytes should be reassessed.
  • Normal hematological analytes may be present in animals with acute hemorrhage in the first 24-36 h, ie animals become hypovolemic but lose all constituents of blood in equal quantities.
  • Volume support should be given and PCV monitored at regular intervals to establish severity of anemia and response.
  • The spleen may falsely elevate red cell count reducing the degree of anemia:
    • Contraction ’ rapid bolus of stored RBC released.
    • Relaxation ’ splenic storage or RBC removing them from circulation (rare).

Signalment
Age

Clinical signs

  • Weakness.
  • Lethargy.
  • Increased pulse rate; bounding pulse.
  • Secondary signs associated with primary cause of anemia, eg renal failure.
  • Mucous membrane pallor.
  • Evidence of hemorrhage.
  • Discolored urine (hematuria, hemoglobinuria).
  • Disease may be subclinical.

Clinical examination

  • Pale mucous membranes.
  • Tachycardia.
  • Bounding pulse.
  • Heart murmur.

Laboratory investigation

  • Where history and clinical signs are suggestive of anemia, or a general health screen suggests anemia, further tests to establish the etiology are carried out in order to establish:
    • Bone marrow response - consider bone marrow aspiration Bone marrow aspiration and/or biopsy.
    • Erythrocyte characteristics.
  • The questions that need to be answered are:
    • Is the anemia regenerative?
    • Is the regeneration adequate for the severity of the disease?
    • Is there increased destruction or loss of red blood cells?
    • What is the cause of the anemia?

Is the anemia regenerative?

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What is the cause of the anemia?

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Is there evidence of hemorrhage?

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Is the anemia non-regenerative?

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Further Reading

Publications

Refereed papers

Other sources of information

  • Knottenbelt C (2001) Investigation of anaemia in dogs. In Practice 23, 306-314.
  • Mills J (2000) Anaemia. In: Manual of Canine and Feline Haematology and Transfusion Medicine. 1st edn. Day M J, Mackin A & Littlewood J D (eds), BSAVA Publications, Gloucester, pp 29-42.


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