Lecture 6: Clinical Approach to the Patient with Anaemia Flashcards
What are 2 ways of classifying anaemia?
1) Basic mechanism
- Impaired production vs blood loss/haemolysis
2) Morphological
- Based on the appearance of the red cells
Describe the different physiological causes for Anaemia
1) Ineffective production
- Deficiency of s_ubstances essential for red cell production_
- e.g. iron, vit 12, folate
-
Genetic defect in red cell production
- e.g. thalassaemia
-
Failure of the bone marrow
- e.g. infiltration
- leukaemia
- irradiation
- drug damage
- e.g. infiltration
2) Impaired red cell survival
- _Blood Los_s
- Usually acute e.g. trauma, surgery
-
Haemolysis
- Shortened survival of the red cell (where the body breaks down RBC)
- Often jaundiced
- Shortened survival of the red cell (where the body breaks down RBC)
If someone is anemic and jaundiced, what type of anaemia is it likely to be?
Haemolytic Anaemia
(lots of breakdown of RBC, so build up of bilirubin)
Describe the Morphologic approach to anaemia
Uses mean cell volume, average cell Hb concentration and blood film comment
-
Microcytic hypochromic anaemia (MCV <76)
- Small RBC, pale anaemia
- Normochromic normocytic anaemia (MCV 76-96)
-
Macroytic anaemia (MCV>96)
- Large RBC
What are the Red Cell Values that we are interested in?
1) Haemoglobin: g/L
2) Red Cell Count
3) Haematocrit or Packed Cell Volume (% of Red cell volume to the whole blood volume)
4) Red Cell Absolute Values
- Mean cell volume
- Mean cell Hb
- Mean cell Hb concentration
What sort of investigations should you do to determine the cause of anaemia?
1) Red Cell values e.g. Hb, Red cell count, Haematocrit, Red cell absolute values
May also look at
2) WBC and platelet count
3) Reticulocyte
4) Examination of the blood film
5) Bone marrow examination
Describe Microcytic Hypochromic Anaemia
Caused when something intereferes with the haemoglobin production
RBC is pale and smaller.
1) Iron deficiency
2) Chronic Illness
- Iron block
3) Genetic
- Thalassaemia
Describe the causes of Microcytic anaemia
explain which part of the RBC each of the causes effects
Iron + Protoporphyrin -> Haem
Iron deficiency, or _chronic inflammatio_n or malignancy can result in less haem = Microcytic Hypochrommic Anaemia
Thalassemia affects the Globin part = Microcytic Hypochrommic Anaemia
How do you diagnose Iron Deficiency? (after finding out that someone has microcytic anaemia)
1) Measure serum iron, ir_on binding capacity (transferrin_), and iron stauration
- *see pic
- Blue(red dots) = Serum ion,
- All = Iron binding capacity/Transferrin level
- Normal
- Iron deficiency
- More transferrin and less ferritin than anaemia of chronic disorders
- Anaemia of chornic disorders
- Different to iron deficiency by looking at the low ferittin levels and the iron transport proteins
- Iron overload
2) Measure serum ferritin
- Soluble storage form of iron
- In iron deficiency, this will be low
3) Rarely examine iron stores in bone marrow
What are the different outcomes of Iron studies?
How can you tell by looking at the blood test if someone has normal, iron deficiency, anaemia of chronic disorders (inflammation) or iron overload?
- Blue = Serum Ion
- Pink = Iron binding proteins/Transferrin
- Green = Serum ferritin
- Normal
-
Iron deficiency
- More transferrin and less ferritin than anaemia of chronic disorders
-
Anaemia of chornic disorders (e.g. oestomylitis, arthritis)
- Lower transferrin and more ferritin than iron deficiency anaemia
-
Iron overload
- No Serum ion
- High ferritin
Explain this lab result
- HB = 50 (anaemia)
- MCV = 62 (mycrocytic)
- MCH = 14 (hypochromic)
- Serum ferritin = low
- Serum iron = low
- IBC (iron binding capacity) = high
- Saturation = low
This indicates low iron stores
Is iron deficiency a diagnosis?
No. We must identify the cause of the deficiency
Anaemia occurs late in iron deficiency
_______ occurs late in _____ deficiency
Anaemia occurs late in iron deficiency
What are the causes of iron deficiency?
1) Diet
- e.g. vegetarian
2) Malabsorption
- proximal small bowel (jejunum)
3) Increased demands
- e.g. pregnancy and breastfeeding
4) Chronic blood loss
- GI or Gu tract
- Doesn’t necessarily present with melena (dark black, tarry feces that are associated with upper gastrointestinal bleeding.)
What are the common causes of iron deficiency in…
1) Children
2) Pre-menopausal females
3) Males and post menopausal females?
Children- Deficient dietary intake
Pre-menopausal females- imblanace between diet intake and menstrual loss
Males and post menopausal female - occult blood loss
How do you treat iron deficiency?
1) Treat underlying cause
2) Iron replacement therapy
-
Oral tablets e.g ferogrradumet
- May be difficult to tolerate
- IV infusion e.g. ferric carboxymaltose
-Haemoglobin concentration increases ~20g/L every 3 weeks
Describe anaemia of chronic inflammation
Sometimes called functional anaemia or I_ron block_
Mild anaemia e.g. 90-100g/L
Normochromic to midly hypochromic
These patients have adaequate amount of iron stores, but i_ron is retained in the macrophages and the marrow_ and not passed into the erythroid cells. It is probably an evolution mechanism, because lots of bacteria use free iron- so we try to reduce these free iron.
Iron studies
1) Normal or raised ferritin
2) Low normal ferritin
3) Low normal TIBC
4) Normal saturation (% of bound and unbound iron)
What is the treatment for Chronic inflammation or malignancy?
Usually Hb doesn’t drop down to the levels where the patient is symptomatic
What is Thalassemia?
One of the causes of microcytic hypochromic anaemia
When there is an i_nherited mutation_ within the a_lpha globin_ or beta globin gene so you have less alpha globin or beta globin chains
= less Hb and they are microcytic and hypochromic.
Heterozygote = Mild anaemia
Homozygous = Severe anaemia
How do you diagnose Thalassaemia?
Lab diagnosis
- Basic haematology, Iron studies, Phenotypic analysis can provide dignosis for either a or B thalassaemia
- Red Cell indices (Hb, RBC, MCH, MCV)
- Haemoglobin protein analysis (Hb electrophoresis, HPLC)
Haemoglobinopathy screen and in selected cases, genetic testing
What are the causes of Macrocytic anaemia?
1) B12 or folate deficiency (megaloblastic anaemia)
2) Liver disease
3) Alcohol
4) Primary bone marrow disorders
5) Hypothyroidism
Describe Megaloblastic anaemia
Due to Vit B12 or Foalte deficiency
Note that the RBC are macrocytic, oval, and there is no effect on the production of haemoglobin.
If it goes on for long enough, can affect other cells e.g. neutrophils (have ore than 3/4 lobes = become hypersegmented)
Describe Vit 12/Folate deficiency
1) impaired DNA synthesis
2) May affect all cell lineages if severe
Diagnosis: measure serum vitamin B12 and folate levels
Need to determine cause of low vit 12 or folate level
What are the causes of low vit B12?
Diet
- vegans
Malabsorption
- Gastrectomy
- Immune (pernicious anaemia)
- There are antibodies against parietal cells and/or intrinsic factor, leading low intrinsic factor
- Terminal ileum disease
- Where intrinsic factor is absorbed
Note that the body has stores for 3-4 years
What are the causes of low folate levels?
1) Diet
- lack of veges
2) Malabsorption
- e.g. coeliac disease
3) Increased demands
- e.g. pregnancy, haemolytic anaemia
Describe Haemolytic Anaemia
1) Shortened survial of red cells
2) Intrinsic defect in te red cell
- E.g. inheritied defect in red cell membrane
3) Envrionmental or extrinsic
- E.g. autoimmune destruction of red cells
Features
- Increased red cell destruction
- Anaemia
- Mild jaundice
- Increase in spleen size
- Increased red cell production
- Raised retriculocyte count
