Red Cells - Part 2 Flashcards
What is anaemia?
Hb below normal range for age and sex
What factors influence reference intervals in range?
Age, sex, ethnic origin, time of day sample taken and time for analysis
What are the reference intervals for haemoglobin for normal?
Male 12-70 yrs is 140-180
Male over 70 yrs is 116-156
Female 12-70 yrs is 120-160
Female over 70 yrs is 108-143
What are the clinical features of anaemia?
Tiredness, pallor, breathlessness, swelling of ankles, dizziness and chest pain
Relating to underlying cause - evidence of bleeding, malabsorption, jaundice and splenomegaly/ lymphadenopathy
Describe the pathophysiology of anaemia
Bone marrow - cellularity, stroma and nutrients
Red cell - membrane, haemoglobin and enzymes
Destruction loss - blood loss, haemolysis and hypersplenism
What are red cell indices?
Automated measurement of red cell size and haemoglobin count
MCH - mean cell haemoglobin
MCV - mean cell volume
What are the morphological descriptions of anaemia?
Hypochromic microcytic - cells are pale and small
Normochromic normocytic
Macrocytic
What tests are done for each morphlogical anaemia type?
Hypochromic microcytic - serum ferritin
Normochromic normocytic - reticulocyte count
Macrocytic - B12/ folate and bone marrow
Describe serum ferritin results
Low - iron deficiency
Normal or increased - thalassaemia secondary anaemia and sideroblastic anaemia
Describe iron metabolism
Absorbed iron - bound to mucosal ferritin + sloughed off or transported across the BM by ferroportin
Then bound to transferrin in plasma
Stored as ferritin mainly in liver
Describe the role of hepcidin
Synthesised in hepatocytes in response to increased iron levels and inflammation - blocks ferriportin so reduced intestinal absorption of iron and mobilisation from RE cells
Describe iron deficiency anaemia
Commonest cause
Description not a diagnosis
Think about bleeding, diet and increased requirements (pregnancy)
What are some clinical features of iron deficiency?
Koilonychia - spoon shaped nails
Atrophic tongue and angular cheilitis
What are causes of iron deficiency anaemia?
GI blood loss, menorrhagia and malabsorption (gastrectomy and coeliac disease)
What is the management of iron deficiency?
Oral iron or IV iron if intolerant
Blood transfusion is rarely indicated
Correct the cause
What can reticulocyte count results show?
Increased - acute blood loss and haemolysis
Normal or low - secondary anaemia, hypoplasia and marrow infiltration
Describe secondary anaemia
70% normochromic normocytic and 30% hypochromic microcytic
Defective iron utilisation - increased hepcidin in inflammation and ferritin normal/ elevated
Identifiable underlying disease - infection, inflammation, malignancy and renal impairment
Describe haemolytic anaemia
Accelerated red cell destruction so decreased Hb
Compensation by bone marrow so increased reticulocytes
Level of Hb - level of red cell production and destruction
Can be extravascular and intravascular
What are the congenital causes of haemolytic anaemia?
Hereditary spherocytosis, enzyme deficiency and haemoglobinopathy
What are some acquired causes of haemolytic anaemia?
Auto-immune haemolytic anaemia - extravascular
Mechanical (artificial valve), severe infection/ DIC and PET/ HUS/ TTP - intravascular
Describe direct antiglobulin test (immune haemolytic anaemia)
Detects antibody or complement on red cell membrane
Reagent contains anti-human IgG or anti-complement
Reagent binds to Ab on red cell surface and causes agglutination in vitro
Explain DAT results
Positive - immune mediated
Negative - non-immune mediated
What does the antibodies in immune haemolysis mean?
Warm auto-antibody - autoimmune, drugs and CLL
Cold auto-antibody - CHAD, infections and lymphoma
Alloantibody - transfusion reaction
What does blood film look like in immune haemolysis?
Spherocytes on film and agglutination in cold
Mostly extravascular
How does intravascular haemolysis look on blood film?
Red cell fragments - schistocytes seen
How is haemolytic anaemia diagnosed?
FBC, reticulocyte count and blood film
Serum bilirubin and LDH
Serum haptoglobin - low
Direct antiglobulin test (DAT)
Urine for haemosiderin/ urobilinogen
What is the management for haemolytic anaemia?
Support marrow function - folic acid
Correct cause - steroids for autoimmune, treat trigger, splenectomy, treat sepsis/ leaky valve and consider transfusion
What does B12/ folate assay results show?
Megaloblastic - B12 deficiency and folate deficiency
Non-megaloblastic - myelodysplasia, marrow infiltration and drugs
What does B12 deficiency cause?
Macrocytic anaemia
Neuro symptoms
Can be pernicious anaemia and gastric/ ilial disease for B12
Folate - dietary, increased requirements and GI pathology
How is vitamin B12 absorbed?
Binds to IF secreted by parietal cells
Complex attaches to IF receptors in distal ileum
Found bound to transcobalamin II in portal circulation for transport to marrow and other tissues
What are the features of megaloblastic anaemia?
Lemon yellow tinge - bilirubin, LDH and red cells friable
Describe pernicious anaemia
Autoimmune disease
Antibodies against intrinsic factor and gastric parietal cells
Malabsorption of dietary B12
Symptoms and signs take 1-2 years to develop
What is the treatment for megaloblastic anaemia?
Replace vitamin - B12 IM injection or oral if not pernicious anaemia
Oral folate
Ensure B12 replaced first if both reduced
What are other causes of macrocytosis?
Alcohol, drugs (methotrexate), disordered liver function, hypothyroidism and myelodysplasia
