Anaemia

The erythrocyte as seen by the routine haematologist is essentially at the final stage of maturation. The "cell" is anucleate, without mitochondria, lysosomes or endoplasmic reticulum (ER), and relies on the Embden-Meyerhof and Heptose Monophosphate pathways to maintain the cell's shape etc.

All cells (except for T cells) are produced in haematopoietic tissue called Bone Marrow. In a child, this is found in the tibia. In an adult, bone marrow is found in the anterior/posterior iliac crest, sternum, ribs, vertebrae and skull.

The bone marrow houses the most primitive haematological cells - called Stem cells. These cells are pluripotential, which means they are able to differentiate into a range of haematological cell types.

The bone marrow is influenced by Erythropoietin produced mostly in the kidneys, but also the liver.

Anaemia is functionally described as a decrease in the competence of blood to carry oxygen to tissues therefore causing tissue hypoxia.
The haematologist looks at haemoglobin, an indirect measure of anaemia:

M = P x S (L)

Where,
M = No./Mass of erythrocytes
P = Production of erythrocytes by the bone marrow
S (L) = Survival (loss) of erythrocytes

Anaemia can be due to a lack of the raw materials necessary for erythrocyte production (eg. iron, vitamin B12 or folate) or because of the presence of chemicals / drugs which affect the stem cell.
A decrease in "M" leads to anaemia.
An increase in "P" = increased erythropoiesis. The marrow can increase production 6-8x to compensate for an anaemic condition.
An increase in "L" can be due to an increase in haemolysis eg. haemolytic anaemia, or because of haemorrhage.

  • Acute Haemorrhage
    • 20% (1000mL) loss with no resting clinical anaemic signs
    • 30-40% (1500-2999mL) loss leads to circulatory collapse and shock
    • 50% loss - death
  • Chronic Haemorrhage
    • eg. Ulcer
    • The body adapts slowly using mechanisms that allow organ function with up to 50% haemoglobin loss. These mechanisms include:
      • Increased Oxygen Flow to Tissues
        • Increase the cardiac output, cardiac rate and circulation rate by decreasing viscosity and peripheral resistance together with preferential blood delivery.
      • Increased Oxygen Flow to Tissues
        • Increase 2,3 DPG producing a shift to the right in the oxygen dissociation curve
The Haematology Profile (HP)
To determine whether the patient is anaemic or not
Factors affecting the components of the HP include...

Haemoglobin (Hb)
Values are higher for a standing patient or if a tourniquet has been applied for too long resulting in haemoconcentration
Decreases after 65yrs, in 2nd and 3rd trimesters of pregnancy and in females

Red Cell Count (RCC)
Varies according to altitude (usually increasing proportionally), age (usually decreasing with increasing age) or smoking (usually increasing)

Haematocrit (Hct)
An absolute increase in plasma volume or an absolute decrease in red blood cells (RBC) may give a low Hct
An absolute decrease in plasma volume with a normal RBC volume may give an elevated Hct
Acute haemorrhage (decreased RBC and plasma volume) may appear normal

Mean Cell Volume (MCV)
Reliable
Relating volume to diameter - spherocytes may have anormal volume but appear with a much smaller diameter

Mean Cell Haemoglobin (MCH)
Does not take into account the size of the cell
Best used with MCV

Mean Cell Haemoglobin Concentration (MCHC)
Concentration of haemoglobin relative to its size
Hb / Hct = Hb / (MCV+RCC) Therefore if increased MCV, MCHC decreases and if decreased MCV, MCHC increases
RBC clumps produce increased MCHC, MCH and MCV with a decreased RCC, and a normal Hb, ie a smaller cell will show a smaller central pallor (hyperchromic-the only cell described as this is the microspherocyte) whilst a larger cell will show a larger central pallor (hypochromic), with a constant Hb
Microspheocytes have decreased MCV and therefore an increased MCHC (constant Hb)

Red Cell Distribution Width (RDW)
Equivalent to anisocytosis in a blood film

White Cell Count (WCC)

A leukaemia can crowd out RBC production leading to anaemia

Validation and Description

Check the results with the request film and the blood film
X10 Power
Scan for evidence of errors in the blood film production
Estimate WCC (1field/4 or 5 fields/20)
X40 Power
Differential
If normal, may stop here
If immature cells are present:
  • Anisocytosis - compare to RDW - Normocytic? (7um), Macrocytic? (>9um), Microcytic? (6um)
  • Poikilocytosis - slight, moderate, marked
  • Haemoglobinisation - colour of RBCs in relation to central pallor (1/3 of area = normal)
  • Immature Forms - NRBC's (nucleated red blood cells); polychromasia -reticulocytes
  • Inclusion Bodies
    • Basophilic Stippling - aggregated ribosomes visualised as bluish-black granular inclusions throughout cellular volume. Can be proportional to chain precipitation in thalassaemia
    • Sideroblastic anaemia
    • Lead poisoning
    • Thalassaemia
    • Abnormal haemoglobin synthesis
    • Enzyme deficiencies
    • Heinz Bodies
       Precipitated or denatured Hb
       Visible fresh as refractile bodies
       Visible in methyl violet/brilliant cresyl  blue/new methylene blue/crystal violet  (supravital stains)
       Invisible with Romanowsky stain
    • Howell Jolly Bodies - dark purple/violet,  spherical, nuclear remnants in RBC  (usually 2 or less, resulting from mitotic  problems)
    • Pappenheimer bodies - small, irregular,  iron containing granules seen with  Romanowsky staining, confirmed with  Prussian blue staining
    • Malarial parasites
New look for June 2003