How to differentiate different types of anaemia based on FBC and other investigation?

How to differentiate different types of anaemia based on FBC and other investigation?


1. Iron Deficiency Anaemia
a. Plasma ferritin

i. A very specific test
ii. Subnormal level is due to iron deficiency, hypothryroidism or Vitamin C deficiency
iii. Can be raised by liver disease andnin an acute phase response (can be up to 100millig/l and still associated with absent bone marrow iron stores
b. Plasma iron and total iron binding capacity (TIBC)

i. Affected by many factors
ii. Low during an acute phase response and raised in liver disease and haemolysis.
c. Transferrin saturation

i. Lowered by malnutrition, liver disease, acute phase response and nephritic syndrome
ii. Raised by pregnancy or OCP
iii. Transferrin saturation of less than 16% is consistent with iron deficiency but is less specific than a ferritin measurement.
d. Transferrin receptors

i. All proliferating cells express membrane tranferrin receptors to acquire iron
ii. Small amount of transferring receptor is shed into blood and found in a free soluble form
iii. At time of poor iron stores, cells up-regulate transferring receptor expression so levels of soluble plasma transferring receptors increase.
iv. Measure by immunoassay


2. Megaloblastic Anaemia

a. Haemoglobin: often reduced, may be very low
b. MCV: usually raised, commonly > 120 fl
c. Erythrocyte count: low for degree of anaemia
d. Blood film: ocal macrocytosis, poikilocytosis, red cell fragmentation, neutrophil hypersegmentation
e. Reticulocyte: low for degree of anaemia
f. Leucocyte: Low or normal
g. Platelet count: low or normal
h. Bone marrow: increased cellularity, megaloblastic changes in erythroid series, giant metamyelocytes, dysplastic megakaryocytes, increased iron in stores, pathological non-ring sideroblasts

3. Anaemia of Chronic Disease

a. Difficult to distinguish anaemia of chronic disease associated with a low MCV from iron deficiency anaemia.
b. Anaemia of chronic disease: increased/normal Ferrition, decreased iron, TIBC, transferring saturation, decreased/ normal soluble transferring receptor
c. Iron Deficiency anaemia: decreased ferritin, iron, transferring saturation, increased TIBC and soluble transferring receptor.