L6: Clinical approach to patient w anaemia Flashcards
Basic mechanism approach to anaemia
Impaired production:
- Deficiency of substances essential for red cell production e.g. iron, vit B12, folate
- Genetic defect in red cell production e.g. thalassemia
- Failure of BM e.g. infiltration (leukaemia, irradiation, or drug damage)
Reduced red cell survival:
- Blood loss (usually acute e.g. surgery, trauma)
- Haemolysis (usually have mild jaundice)
Morphological approach to anaemia
Uses: MCV, average cell Hb conc and blood film comment
- Microcytic hypochromic anaemia = MCV < 76
- Normochromic normocytic anaemia = MCV 76-96
- Macrocytic anaemia = MCV > 96
Red cell values
- Haemaglobin: g/L
- Red cell count
- Haematocrit = PCV
Red cell absolute values: - Mean cell volume (MCV)
- Mean cell Hb (MCH)
- Mean cell Hb conc (MCHC)
Other investigations = WBC and platelet count, reticulocyte count, examination of blood film, bone marrow examination
Microcytic anaemia causes
- Iron deficiency
- Chronic illness - iron block
- Genetic - thalassemia
Diagnosis of iron deficiency
- Measure serum iron, iron binding capacity (transferrin) and iron saturation
- Measure serum ferritin
- Rarely examine iron stores in bone marrow
Classic pattern: low serum iron, high iron binding capacity and low ferritin
Causes of iron deficiency
- Diet e.g. vegetarian
- Malabsorption (proximal small bowel)
- Increased demands e.g. pregnancy
- Chronic blood loss (GI or GU)
Children: deficient diet intake
Pre-menopausal females: imbalance between diet and menstrual loss
Males and post-menopausal females: occult blood loss
Treatment of iron deficiency
Iron replacement therapy
- Oral tablets e.g. ferrogradumet
- IV infusion e.g. ferric carboxymaltose
= increase in Hb conc by 20g/L every 3 weeks
Anaemia of chronic inflammation
- “Iron block”
- E.g. underlying malignancy of inflammatory disease (e.g. rheumatoid arthritis)
- Mild anaemia e.g. 90-100g/L
- Normochromic to mildly hypochromic
- Iron studies: normal/raised ferritin, low normal iron, low normal TIBC, noraml saturation
- Treatment: of underlying condition
Thalassemia
- Inherited mutation within either a-globin or b-globin gene
- One or both alpha or beta chains reduced/absent = reduced Hb
- Autosomal recessive disorder
- Heterozygote: mild anaemia
- Homozygous: severe anaemia (transfusion-dependent)
- Lab diagnosis: haemoglobinopathy screen and in selected cases genetic testing
- Homozygous beta-thalassemia = enlargement of liver and spleen, skull changes
Diagnostic strategies for thalassemias
- Basic haematology, iron studies and phenotype analysis should provide initial diagnosis of alpha or beta
Red cell indices:
- Hb, RBC, MCH, MCV
- Blood film examination
Hb protein analysis:
- Hb electrophoresis
- HPLC: Hb A2, abnormal peaks
Causes of macrocytic anaemia
- B12/folate deficiency (megaloblastic anaemia)
- Liver disease
- Alcohol
- Primary bone marrow disorders
- Hypothyroidism
Megaloblastic anaemia
- Deficiency of B12 or folate
- Large, oval cells
- No effect on production of Hb, only reduced erythropoiesis
- If severe enough for a long time can affect other dividing cells (e.g. hypersegmented neutrophils)
- Impaired DNA synthesis
- Diagnosis: measure serum B12 and folate
- Treatment: treat underlying cause
Causes of low B12
Diet e.g. vegan Malabsorption: - Gastrectomy - Immune (pernicious anaemia - ABs against parietal cells or intrinsic factor) - Terminal ileum disease (body has stores for 3-4yrs)
Treatment = IM injections of B12 (unless diet)
Causes of low folate
- Diet e.g. lack of vege
- Malabsorption e.g. coeliac disease
- Increased demand e.g. pregnancy, haemolytic anaemia
Treatment = oral supplement
Haemolytic anaemia
- Shortened survival of red cells
- Intrinsic defect in red cell (e.g. inherited defect in cell membrane)
- Environmental or extrinsic (autoimmune destruction of red cells)
Features:
- Increased RBC destruction = anaemia, mild jaundice, increased spleen size
- Increased RBC production = raised reticulocyte count
