Full Blood Count Interpretation

Hypochromic/Microcytic Blood Picture

  Hb MCV MCH RBC RDW
Iron Deficiency Anaemia      -     -      - N or -     +
Thalassaemia Trait N or -     -      - N or -      N
Secondary Anaemia (chronic disease, cancer, renal failure etc)   N or - N or -    

A useful 'discriminant function' to distinguish iron deficiency and thalassaemia trait (applicable only to non-pregnant adults) may be obtained using the following formula:

X = MCV - (5 x [Hb]) - 3.4

iron deficiency would be suggested if X is positive
thalassaemia trait would be suggested if X is negative

Macrocytic Blood Pictures

  Hb MCV RBC RDW
Megaloblastic anaemia (e.g. B12 or folate deficiency)  -  +    
Alcohol abuse N  + N N

Other causes of macrocytosis include: myelodysplasia (suspect in the older patient with anaemia ± abnormal WBC and platelet count), liver disease and hypothyroidism.

What do the comments of a blood film mean?

Term Meaning Possible Significance

anisocytosis

variation in cell size

corresponds to raised RDW (see Full Blood Count)

poikilocytosis

variation in cell shape

may be diagnostic (e.g. spherocytes)

macrocytosis

raised red cell volume

B12/folate deficiency, ethanol, hypothyroidism

microcytosis

reduced red cell volume

iron deficiency, thalassaemia trait

rouleaux

'chains' of red cells

raised protein in plasma e.g. myeloma, inflammation

agglutination

'clumped' red cells

col autoagglutination

spherocytes

small round red cells

hereditary, autoimmune

elliptocytes

rod shaped red cells

hereditary, elliptocytosis

target cells

dark centre to red cells

thalassaemia, liver disease, iron deficiency, Hb C (Afro-Caribbeans)

polychromasia

large basophilic red cells

immature red cells (bleeding, haemolysis)

Howell Jolly bodies

nuclear remnants in red cells

post-splenectomy, hyposplenism

Heinz bodies

denatured haemoglobin

oxidative haemolysis (e.g. G6PD deficiency)

Burr cells

irregularly crenated red cells

renal failure, hypothyroidism

acanthocytes

spiky red cells

liver disease

shistocytes

red cell fragments

mechanical e.g. prosthetic heart valves, DIC

left shift

myelocytes and meta-myelocytes in film

infection, marrow infiltration

right shift

hypersegmented polymorphs

megaloblastic anaemia

toxic granulation

increased granulation in neutrophils

implies bacterial infection


Page updated: 04/04/2011 Updated by: Michael O'Sullivan

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