Investigation findings Flashcards
Define the following parameters on RBC indices:
- RBC Count
- Haemoglobin
- Haematocrit
- MCV
- MCH
- MCHC
- RDW
- RBC Count: concentration of RBCs in whole blood
- Haemoglobin: concentration of Hb in whole blood
- Haematocrit: % of blood volume that consists of intact RBCs
- MCV (mean cell volume): average volume of a single RBC
- MCH (mean cell haemoglobin): average amount of Hb in a single RBC
- MCHC (mean cell Hb concentration): average concentration of Hb in a single RBC (In contrast to MCH, MCHC correlates the hemoglobin content with the volume of the cell.)
- RDW (red cell distribution width): measure of variation in RBC size
Why is the red cell count not a useful parameter?
Does not reflect the oxygen-carrying capacity of the blood (this is better exemplified by haemoglobin)
Name and describe 2 pathologies that can raise the packed cell volume/haematocrit
Polycythemia: excess iron in the body
Haemochromatosis: excess haemoglobin in the body
Why does red cell distribution width change in inflammatory states?
Impaired erythrocyte maturation
What is the reticulocyte count? What does it indicate?
Number of immature RBCs. Indicates that more RBCs are being made (i.e. due to anaemia).
When is it inappropriate for the reticulocyte count to be normal?
When the iron studies show that someone is anaemic; in this situation, the reticulocyte count SHOULD be elevated because it is a normal physiological response to blood loss.
Makes you suspicious that something is suppressing the bone marrow.
Reticulocytes can contribute to a ____cytosis
Reticulocytes can contribute to a MACROcytosis
List the components of an iron study and explain what each represents
Serum iron: iron in the blood (not a useful marker as it fluctuates a lot)
Ferritin: iron storage protein (can hold thousands of molecules of iron). Also elevated as an acute phase reactant (inflammation).
Transferrin: transporter protein for iron
Transferrin saturation: proportion of transferrin currently bound to iron (how much is being utilised?)
Name the 2 types of polycythemia and give examples of the causes
- Polycythemia vera / primary polycythemia: problem is occurring within the bone marrow (e.g. bone marrow mutation that is producing excess RBCs, JACK-2 is most common)
- Secondary polycythemia: factors external to RBC production (e.g. COPD/smoking causing chronic hypoxemia, renal cell carcinoma impairing EPO production, EPO doping)
Name 6 markers that are raised during haemolysis
- Raised LDH (generic marker of cell turnover)
- Anaemia
- Increased free Hb (not inside a red cell)
- Haptoglobin
- Bilirubin
- DAT
What is haptoglobin? Why is it undetectable in significant haemolysis?
A protein produced by the liver which is designed to bind free Hb (Hb is toxic on its own).
Undetectable haptoglobin means that it is completely consumed due to haemolysis of RBCs and raised levels of free Hb.
Why is bilirubin raised in haemolytic states?
Bilirubin is released as haeme molecules are released and broken down
What is a DAT test? What does it show?
DAT = direct antiglobulin test.
Measures whether antibodies or complement are attacking the RBCs. Leads us to believe that there’s autoimmune haemolysis.
Name 3 broad categories of the causes of thrombocytopenia.
BONE MARROW CAUSES
SECONDARY SUPPRESSION OF BONE MARROW
PERIPHERAL CONSUMPTION / DESTRUCTION
Give examples of things which would fit into each of the following categories of thrombocytopenia:
BONE MARROW CAUSES
SECONDARY SUPPRESSION OF BONE MARROW
PERIPHERAL CONSUMPTION / DESTRUCTION
BONE MARROW CAUSES: nutrient deficiencies (e.g. B12, folate), haematological malignancy, aplastic anaemia
SECONDARY SUPPRESSION OF BONE MARROW: sepsis/bacterial suppresion, medications, inflammatory states
PERIPHERAL CONSUMPTION / DESTRUCTION: ITP, H. Pylori, DIC, chronic liver disease
What is an IPF? What is it useful for?
IPF = immature platelet fraction. IPF to platelets is what reticulocytes are to RBCs.
IPF indicates whether the bone marrow is appropriately responding to thrombocytopenia. If there is platelet destruction, we should see a rise in IPF as the body tries to compensate.
A normal IPF despite thrombocytopenia indicates that the bone marrow is NOT responding appropriately - there is some BM suppression or a diseased state.
Name and describe the 2 categories of thrombocytosis
Primary / Autonomous / Essential thrombocytosis (ET): genetic mutations causes bone marrow to over-produce platelets
Secondary / Reactive thrombocytosis: excess platelets due to another underlying condition (e.g. infection, malignancy, anaemia)
What is pancytopenia?
Deficiency of all 3 components of blood (red cells, white cells, platelets)
Name 3 causes of pancytopenia
BONE MARROW FAILURE (most common): e.g. leukaemia, lymphoma, aplastic anaemia
SEVERE NUTRITIONAL DEFICIENCIES: B12, folate (rare in developed countries)
PERIPHERAL DESTRUCTION OF CELLS: e.g. hypersplenism (all cells being consumed)
What is aplastic anaemia?
Rare condition in which the body stops producing new RBCs
List the causes of MICROCYTIC anaemia using the ‘TAILS’ acronym
T - thalassemia A - anaemia of chronic disease I - iron-deficiency anaemia L - lead poisoning S - sideroblastic anaemia
List the causes of MACROCYTIC anaemia using the acronym ‘FAT RBC’
F - foetus (pregnancy)
A - alcohol
T - thyroid disease (hypo)
R - reticulocytosis
B - B12 deficiency
C - cirrhosis and chronic liver disease
List the causes of NORMOCYTIC anaemia (AAAHH)
A - acute blood loss (haemorrhage) A - anaemia of chronic disease A - aplastic anaemia H - hypothyroidism H - haemolytic anaemia
What are megaloblasts?
Large, immature RBCs
https://www.youtube.com/watch?v=Vh1LZlLCfkU
When would the reticulocyte count be high?
Blood loss
Iron deficiency
Haemolysis
When would the reticulocyte count be low?
Bone marrow disorders, e.g. aplastic anaemia
List 3 causes of aplastic anaemia
Chemotherapy or radiotherapy Drugs (e.g. methotrexate, antibiotics) Autoimmune disorders Pregnancy Viral infection (e.g. EBV)
Name 3 causes of megaloblastic anaemia
B12 deficiency
Folate deficiency
Drug-induced
Name 4 causes of non-megaloblastic anaemia
Reticulocytosis (e.g. haemolysis)
Alcohol
Liver disease
Hypothyroidism
