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OutiLaine

MarjattaSinisalo

Assessment of Anaemia in Adults

Anaemia is the most common blood-related finding encountered in outpatient care, iron deficiency anaemia is the most common form of anaemia, and anaemia associated with a chronic disease (secondary anaemia) is the next most common form.
The essential questions in the assessment of anaemia are:
- What is the type of anaemia (according to automated MCV determination)?
  - Microcytic (MCV < 80 fl)
  - Normocytic (MCV 80-100 fl)
  - Macrocytic (MCV > 100 fl)
- What is the mechanism (decreased production or increased destruction of red cells)?
- What is the diagnosis: the pathophysiology and underlying cause of the anaemia?
See picture Assessment of Anaemia in Adults.

The prevalence of anaemia varies considerably, depending on the population studied. It is more common in women and often a "side diagnosis". The WHO criteria for anaemia are as follows:
- children; blood haemoglobin < 110 g/l
- women; blood haemoglobin < 120 g/l, during pregnancy < 110 g/l
- men; blood haemoglobin < 130 g/l
However, even the lower haemoglobin levels may be normal. For instance, in Finland the following reference ranges are used: 117-155 g/l for women and 134-167 g/l for men.
In many patient series, iron deficiency is found to be the most common mechanism of anaemia (about 50% of patients in ambulatory care). The cause of iron deficiency must be identified.
Anaemia is not a final diagnosis, but rather a symptom of an illness/disorder.
The lowering of a patient's haemoglobin value by more than 20 g/l from his/her normal level can similarly be regarded as a symptom, even if the haemoglobin value is still within reference range.

Anaemia may result from increased destruction of red cells (haemorrhage or haemolysis), poor production of red cells in the bone marrow or both.

Morphological classification of anaemias according to the mean corpuscular volume of erythrocytes (MCV) is a simple and practical approach to the assessment of anaemia.

Microcytic anaemias (MCV < 80 fl)
- Iron deficiency
- A small share of anaemias of chronic disease (ACD)
- Thalassaemias
Normocytic anaemias (MCV 80-100 fl)
- Most cases of ACD
- Most cases of haemolytic anaemia
- Acute haemorrhage
- Aplastic anaemia or bone marrow infiltration
Macrocytic anaemias (MCV > 100 fl)
- Vitamin B₁₂ deficiency
- Folate deficiency
- Blood loss (bleeding or haemolysis that has occurred > 2 days ago causes reticulocytosis that is manifested as mild macrocytosis)
- Liver disease
- Heavy alcohol consumption
- Other causes (myelodysplasia, haematologic malignancy, hypothyroidism)
- Macrocytosis without anaemia, see Macrocytosis (Increased MCV).

If the anaemia is microcytic, no chronic disease can be found and ESR is not elevated, iron deficiency anaemia is most probableIron Deficiency Anaemia. The prevalence of thalassaemia syndromes must however be taken into account.
Full blood count should be performed, except in clear cases of iron deficiency anaemia.
Macrocytosis associated with anaemia often suggests megaloblastic anaemia Megaloblastic Anaemia.
The most common normocytic anaemia is the anaemia of chronic disease, i.e. secondary anaemia Anaemia of Chronic Disease (ACD). In normocytic anaemia, reticulocytosis strongly suggests bleeding or haemolysis Haemolytic Anaemia whereas reticulocytopenia suggests impaired erythrocyte production (e.g. secondary anaemia or disturbance of production in bone marrow).
Bone marrow examination is seldom needed in the assessment of anaemia if there are no other cytopenias. If the aetiology of the anaemia is not revealed by complete blood count, by the concentrations of ferritin, transferrin saturation, transferrin receptors, vitamin B₁₂ and serum folate, or by tests for haemolysis, and the patient does not have any systemic disease that would explain for chronic anaemia, bone marrow examination is indicated.