The neurology

Anaemia is defi ned by the haemoglobin concentration in peripheral blood being below the normal 14 gm/dL (SD ± 2) for women, 16 gm/dL (SD ± 2) for men and 12 gm/dL (SD ± 2) for children. The number of red blood cells is also usually reduced, below the normal 4.8 × 10/mm (SD ± 0.6) for women and 5.4 × 10/mm (SD ± 0.9) for men. The haematocrit is the proportion of red blood cells in the blood – normally more than 40% for men and 37% for women. The other major red blood cell indices that may be helpful in the differential diagnosis of anaemia are: • the mean corpuscular volume (MCV), which is the average red blood cell size and is normally 87 u (SD ± 5); • the mean corpuscular haemoglobin (MCH), which is the amount of haemoglobin per cell, normally 29 pg of haemoglobin/cell (SD ± 2); • the mean corpuscular haemoglobin concentration (MCHC), which is the average concentration of haemoglobin per cell, normally 34% (SD ±2). Although these indices may be useful, they are only averages and complete evaluation requires microscopic examination of the peripheral blood smear which will reveal: • red blood cell size (macrocytosis, microcytosis) and shape, as well as their maturity (i.e. reticulocytes or nucleated cells); • the intensity of haemoglobin staining (hypochromia, normochromia or hyperchromia) • the presence of macrocytes, target cells, spherocytes, schistocytes or other abnormally shaped cells. In some situations, automated analysis of the erythrocyte indices may be normal, but the peripheral blood smear shows a dimorphic The neurology