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CLASSIFICATION OF ANAEMIAS AND POLYCYTHAEMIAS


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  • Anaemia in an individual is defined as a haemoglobin (Hb) concentration in blood that is below the expected value, when age, gender, pregnancy and certain environmental factors, such as altitude, are taken into account
  • Anaemia is defined based on haemoglobin concentration and not PCV

WHO Criteria for Anaemia, Based on Normal Haemoglobin Range at Sea

Level

 

 

Age/gender

Normal haemoglobin range

(g/dl)

Anaemic if Hb range less than: (g/dl)*

Birth (full-term)

13.5-18.5

13.5 (Hct 34.5)

Children: 2-6 months

9.5-13.5

9.5 (Hct 28.5)

Children: 6 months-6 years

11.0-14.0

11.0 (Hct 33.0)

Children: 6-12 years

11.5-15.5

11.5 (Hct 34.5)

Adult males

13.0-17.0

13.0 (Hct 39.0)

Adult females: non-pregnant

12.0-15.0

12.0 (Hct 36.0)

Adult females: pregnant

 

 

First trimester: 0-12 weeks

11.0-14.0

11.0 (Hct 33.0)

Second trimester: 13-28 weeks

10.5-14.0

10.5 (Hct 31.5)

Third trimester: 29 weeks-term

11.0-14.0

11.0 (Hct 33.0)

 

CLASSIFICATION OF ANAEMIA

  • Based on cause
  • Based on red cell indices

Classification Based on Cause

  • Inadequate production of red blood cells
    • Marrow failure e.g. aplastic anaemia
    • Nutritional deficiency – iron, folate, Vit B12
    • Metabolic disturbances – infections
    • Malignancies – acute leukaemia, lymphoma, etc.
  • Excessive loss of red blood cells
    • Haemorrhage – DIC[1], haemophilia, PPH
    • Haemolysis – sickle cell disease, autoimmune haemolytic anaemia, etc.

Classification Based on Red Cell Indices (Morphological Classification of Anaemia)

  • More useful than the classification based on cause of anaemia
  • It has 2 major advantages;
    • It suggests the nature of the underlying defect and therefore the particular investigations which would be most useful in confirming the diagnosis
    • Abnormal red cell indices may suggest an underlying abnormality before anaemia develops
  • Microcytic hypochromic anaemia (MCV < 76fl, MCH < 27pg)
    • Iron deficiency anaemia
    • Thalassaemia
    • Sideroblastic anaemia
    • Anaemia of chronic disorders
  • Normocytic normochromic anaemia (normal MCV and MCH)
    • Haemolytic anaemias
    • Acute blood loss
    • Mixed deficiencies
    • Bone marrow failure
  • Macrocytic anaemia (MCV > 96fl)
    • Megaloblastic anaemia (Folate or B12 deficiency)
    • Non-megaloblastic (alcohol, liver dx[2], MDS[3], aplastic anaemia)

GENERAL SYMPTOMS OF ANAEMIA

  • Shortness of breath particularly on exercise
  • Weakness
  • Lethargy
  • Palpitation
  • Headache
  • Visual disturbances secondary to retinal haemorrhage in very severe anaemia

GENERAL SIGNS OF ANAEMIA

  • Pallor of mucous membranes
  • Tachycardia
  • Bounding pulse
  • Cardiomegaly
  • Systolic flow murmur

POLYCYTHAEMIA

  • Polycythaemia is defined as an increase in the haemoglobin concentration above the upper limit of normal expected for the patient’s age and sex, usually accompanied by rise in red cell count and PCV
  • PCV is >48 or >54% in Female and Male respectively
  • Haemoglobin concentration is >16.5 or >18.5g/dl in Female and Male respectively
  • Increase in the proportion of blood volume that is occupied by red blood cells
  • Absolute polycythaemia – due to increase in the number of red blood cells
  • Relative polycythaemia – due to decrease in the plasma volume

 

  • Primary familial (congenital) polycythaemia – a rare condition in which there is a genetic mutation which creates abnormal oxygen sensing with increased erythropoietin production

Secondary

  • Due to compensatory Epo[4] increase (Hypoxic 2° Polycythaemia)
    • High altitude
    • Sleep apnoea
    • Chronic obstructive airway disease
    • Cyanotic congenital heart disease
    • High oxygen affinity haemoglobins
    • Methaemoglobinaemia
    • Red cell metabolic defects e.g. ↓ 2,3DPG
    • Chronic carbon monoxide poisoning e.g. heavy smoking
  • Due to inappropriate Epo secretion
    • Renal diseases e.g. renal cysts, polycystic kidneys, renal artery stenosis, hydronephrosis, renal tumours
    • Tumours such as uterine leiomyoma, hepatocellular ca[5], cerebellar haemangioblastoma
  • Miscellaneous causes of 2° Polycythaemia
    • Neonatal polycythaemia ü Androgen therapy
    • Cushing’s disease
    • Truncation of erythropoietin receptor
    • Hypertransfusion

Relative Polycythaemia (Pseudo or Apparent Polycythaemia)

  • Dehydration – water deprivation, vomiting
  • Stress
  • Diuretic therapy
  • Plasma loss – burns, enteropathy
  • Cigarette smoking
  • Giasbök syndrome – mild obesity, diastolic hypertension, ↓ in plasma volume

 

[1] Disseminated Intravascular Coagulation

[2] dx – disease(s)

[3] MDS – Myelodysplastic syndrome

[4] erythropoietin

[5] cancer