Approach to Anaemia Diagnosis Flashcards
What is anaemia?
Reduced haemoglobin concentration that is not optimal for that individual
(usually <95% range for the population)
What are the normal Hb concentrations in children?
6 months - 6 years = 110g/L
6-14 years = 120 g/L
What is the difference in normal Hb concentrations between females who are and are not pregnant?
Not pregnant - 120
Pregnant - 110
What would you identify in a patient’s blood count if the anaemia is part of a wider bone marrow production problem?
Check rest of the blood count for pancytopenia
How can anaemia be classified
Decreased production
- Hypoproliferative (decreased erythropoiesis)
- Maturation abnormality (cytoplasm/nuclear)
Loss/destruction of RBCs
- Bleeding
- Haemolysis
What type of blood count can show there is increased red cell production due to stress on bone marrow?
Reticulocyte count
- shows RBCs trying to regenerate due to depletion
Loss or destruction of RBCs will induce a reticulocytosis. What should you look for to distinguish between these two causes for a high retic. count?
Blood breakdown products
- bilirubin
- urinary urobilinogen
- this tells you haemolysis is occurring
By how much can the bone marrow increase its normal level of cell production?
3-4 fold
By how much can reticulocyte count be increased from normal in times of need?
6-8 fold
What are the causes of a hypochromic microcytic anaemia?
Iron deficiency
Thalassemia (globin deficiency)
Prophyrin ring abnormality (lead poisoning)
Why does iron deficiency cause cells to be small?
- Less iron to make Hb
- Hb doesnt attach to RBC => required concentration of Hb NOT reached
- Hb conc. would normally cause the nucleus to leave the cell
- instead nucleus causes further cell divisions that make the cell smaller than normal
What are the potential causes of a macrocytic anaemia?
- Nuclear maturation defects - failure of cell division
- Nutritional - B12/folate (megaloblastic anaemias)
- Myelodysplasia
- Drugs eg chemotherapy (attempt to slow cell division)
What can cause an apparent or false macrocytosis?
- Agglutination => RBCs clump and are counted as one
- Reticulocytosis => larger than average mature RBC
What can cause a macrocytosis without significant anaemia?
- Hypothyroidism
- Alcohol
- Liver disease
WHat are the causes of a normocytic anaemia?
Hypoproliferative => Marrow failure => Hypometabolic (e.g. anorexia) => Marrow infiltration (malignancy) => Renal impairment => Anaemia of Chronic disease (inflammatory, infection, malignancy)
What is meant by a renal anaemia?
Anaemia due to reduced erythropoietin production
this may be considered an anaemia of chronic disease of the kidney
Explain how an anaemia of chronic disease occurs.
- disease flares
- inflammation occurs (+ cytokines released)
- increases hepcidin
- this binds to ferroportin and stops iron being released from cells
- iron therefore cant be used to make Hb
=> patient becomes anaemic
Why may some patients with an anaemia of chronic disease have a microcytic picture?
- reduced release of iron from macrophages ie failure of Hb synthesis
=> cells undergo extra divisions without Hb attached - low transferrin saturation BUT normal/raised ferritin
- These pts may respond to IV iron
Why are many reticulocyte counts not actually carried out in practice?
- Many anaemias hypoproliferative
- acute blood loss can usually be seen, which will in turn generate a high reticulocyte count
- a reticulocyte count can be used if suspecting haemolysis in a patient
HOw can patients have and MCV in normal range yet still have a microcytic anaemia?
Microcytosis can be a relative rather than absolute term
- iron deficient pts have normal range MCV (BUT not normal for the individual - it may be significantly lower than a previous result)
Why may it be difficult to distinguish what is causing a patient’s anaemia?
- more than one factor is present that could be the cause
E.g.
- Rheumatoid arthritis patient (anaemia of chronic disease)
- Taking Methotrexate (folate antagonist)
- Taking NSAID causes occult GI blood loss secondary to gastropathy (iron deficiency)
HOw can iron deficiency anaemia and anaemia of chronic diseas be distinguished by blood tests?
Iron deficiency:
- Normal/Increased amount of transferrin
- reduced ferritin stores
Anaemia of Chronic Disease:
- Normal/reduced transferrin
- Normal/Increased iron stores
In what order should you do investigations for anaemia?
- Name (gives indication of ethnicity)
- Age
- Presenting complaint and clinical findings
- FBC - check Hb, MCV, any other cytopenias?
- Reticulocyte count (if required)
- Blood film
- Haematinics (ferritin/B12/folate)
- Special tests, bone marrow
