Red Cell Count (RCC)

Interpretation is required to be made in conjunction with the other red cell parameters below.

Packed Cell Volume (PCV)

PCV is reduced in anaemia and increased in erythrocytosis. In patients with erythrocytosis, the PCV correlates with blood viscosity.

Mean Cell Volume (MCV)

Macrocytosis (high MCV) is found in:

• Megaloblastic, aplastic, dyserythropoietic and sideroblastic anaemias
• Myelodysplastic syndromes, myeloma; liver disease, alcohol excess
• Chronic hypoxic lung disease
• Myxoedema; following renal transplant
• Cytotoxic drug therapy particularly hydroxyurea, therapy with Zidovudine (AZT).

Microcytosis (low MCV) is found in:

• Iron deficiency
• Anaemia of chronic disease
• Haemoglobinopathies (especially the thalassaemias).

Mean Cell Haemoglobin (MCH)

Arithmetically, MCH is Hb divided by RCC. The MCH is increased in macrocytic anaemias and decreased in microcytic anaemias. If the MCH is significantly abnormal then a blood film should also be requested.

Mean Cell Haemoglobin Concentration (MCHC)

Arithmetically, MCHC is Hb divided by PCV. There is a rough correlation between low MCHC and hypochromia and between high MCHC and the presence of spherocytes.

Red Cell Distribution Width (RDW)

The RDW may assist in the classification of anaemia, in association with the blood film, and the other red cell indices (MCV, MCH and MCHC). The RDW gives a quantitative assessment of the degree of variation in red cell size / volume (anisocytosis).

White Cell Count (WCC/TWDC)

The interpretation is required to be made in conjunction with the differential count of white cells below:

• Neutrophils
• Lymphocytes
• Monocytes
• Basophils
• Eosinophils
• Platelets