The first and foremost investigation in any suspected case of anaemia is to carry out the hemoglobin estimation. Several methods are available but most reliable and accurate is the cyanmethaemoglobin (HiCN) method employing Drabkin’s solution and a spectrophotometer. If the hemoglobin value is below the lower limit of the normal range for particular age and sex, the patient is said to be anaemic.
Where there is neither reouleaux formation nor so thin as to cause red cell distortion. Such an area can usually be found towards the tail of the film, but not actually at the tail.
The following abnormalities in erythroid series of cells are particularly looked for in a blood smear:
1. Variation in Size (Anisocytosis):
Normally, there is slight variation in diameter of the biconcave disc shaped red cells from 6.7-7.7 mm (mean value 7.2 mm). Increased variation in size of the red cell is termed anisocytosis. Anisocytosis may be due to the presence of cells larger than normal (macrocytosis) or cells smaller than normal (microcytosis).
Sometimes both microcytosis and macrocystosis are present (dimorphic):
i. Macrocytes are classically found in megaloblastic anaemia; other causes are aplastic anaemia, other dyserythropoietic anaemia, chronic liver disease and in conditions with increased erythropoiesis.
ii. Microcytes are present in iron-deficiency anaemia, thalassaemia and spherocytosis. They may also result from fragmentation of erythorcyes such as in haemolytic anaemia.
2. Variation in Shape (Poikilocytosis):
Increased variation in shape of the red cells is termed poililocytosis. The nature of the abnormal shape determines the cause of anaemia. Poikiocyts are product in various types of abnormal erythropoiesis. e.g. in megaloblastic anaemia, iron-deficiency anaemia, iron-deficiency anaemia, thalassaemia, myelosclerosis and microangiopathic haemolytic anaemia.
3. Inadequate Haemoglobin Formation (Hypochromasia):
Normally, the intensity of pink staining of haemoglobin in a Romanowsky-stained blood smear gradually decrease from the periphery to the centre of the cell. Increased central pallor is referred to as hypochromasia.
It may develop either from lowered haemoglobin content (e.g. in iron-deficiency anaemia, chronic infections), or due to thinness of the red cells (e.g. in thalassaemia, sideroblastic anaemia).
Unusually deep pink staining of the red cells due to increased haemoglobin concentration is termed hyperchromasia and may be found in megaloblastic anaemia, spherocytosis and in neonatal blood.
4. Compensatory Erythropoiesis:
A number of changes are associated with compensatory increase in erythropoietic activity.
These are as under:
(i) Polychromasis is defined as more than one type of colour in the red cells. Polychromatic red cells are slightly larger, generally stain bluish-grey and represent reticuocyes and, thus correlate well with reticulocyte count.
(ii) Normoblastaemia is presence of nucleated red cells in the periphera blood film. A small number of normoblasts (or erythroblasts) may be normally found in cord blood at birth. They are found in large numbers in haemolytic disease of the newborn, other haemolytic disorders and in extra-medullary erythropoiesis. They may also appear in the blood in various types of sever anaemia’s except in aplastic anaemia. Normoblastaemia may also occur after splenectomy.
(iii) Punctate basophillia or basophilic stippling is diffuse and uniform basophilic granularity in the cell which does not stain positively with Perl’s reaction (in contract to Pappehneimer bodies which stain positively). Classica punctuate basophillia is seen in aplastic anaemia, thalassaemia, myelodysplasa, infection and lead poisoning.
(iv) Howell-jolly bodies are purple nuclear remnants, usually found singly, and are larger than basophilic stippling. They are present in megaloblastic anaemia and after splenectomy.
5. Miscellaneous Changes:
In addition to the morphologic abnormalities of red cells described above, several other abnormal red cells may be found in different haematological disorders.
Some of these are as follows (Fig. 23.2):
(i) Spherocytosis is characterized by presence of spheroidal ratherthan biconcave disc-shaped red cells. Spherocytes are seen in hereditary spherocytosis, autoimmune haemolytic anaemia and in ABO haemoytic disease of the newborn.
(ii) Schistocytosis is identified by fragmentation of erythrocytes. Schistocytes are found in thalassaemia, hereditary eliptocytosis, megaloblastic anaemia, iron-deficiency anaemia, microangiopathic haemolytic anaemia in severe burns.
(iii) Irregularly contracted red cells are found in drug and chemical-induced hemolytic anaemia and in unstable haemoglobinopathies.
(iv) Leptocytosis is the presence of unusually thin red cells. Leptocytes are seen in severe iron deficiency and thalassaemia. Target cell is a form of leptocyte in which there is central round stained area and a peripheral rim of haemoglobin. Target cells are found in iron deficiency, thalassaemia, chronic disease, and after splenectomy. Thalassaemia, chronic liver disease, and after splenectormy.
(v) Stick cells or drepanocytes are stickle-shaped red cells found in sickle cell disease.
(vi) Crenated red cells are the erythrocytes which develop numerous projections from the surface. They are present in blood films due to alkaline pH < presence of traces of fatty substances on the slides and in cases where the film is made from blood that has been allowed to stand overnight.
(vii) Acanthocytosis is the presence of coarsely crenated red cells. Acanthocytes are found in large number in blood film made from splenectomised subject, in chronic liver disease and in abetalipoproteinaemia.
(viii) Burr cells are cell fragments having one or more spines. They are particularly found in uraemia and in pyruvate kinase deficiency.
(ix) Stomatocytosis is the presence of stomatocytes which have central area having slit-like or mouth like appear ance. They are found in alcoholism or as an artifact.
(x) Ovalocytosis or elliptocytosis is the oval or elliptical shape of red cells. Their highest proportion (79%) is seen in hereditary ovalocytosis and elliptocytosis; other conditions showing such abnormal shapes of red cells are megaloblastic anaemia and hypochromic anaemia.