red blood cell parameters

Question 1

how is blood taken (2)

Answer 1

.venous sample

.finger/heel prick

Question 2

what is MCHC

Answer 2

Mean Cell Haemoglobin Concentration (g/l)

Question 3

what is Hct

Answer 3

haematocrit (packed cell volume). l/l

Question 4

what are the units for Hb

Answer 4

g/l

Question 5

how was WBC,RBC and platelet count traditionally calculated

Answer 5

done visually under microscope using a diluted blood sample

Question 6

how is WBC,RBC and platelet count now calculated

Answer 6

large automated instruments via enumerating (finding the number of) electronic impulses generated when cells flow between a light source/electric field

Question 7

how was Hb traditionally measured

Answer 7

.spectrometer
converting hb to a stable form
. then measuring light absorption at a specific wavelength

Question 8

how is hb now measured

Answer 8

automated instrument (same principle)

Question 9

how was Hct (haematocrit) measured

Answer 9

centrifuging blood sample

Question 10

what should a blood count be followed up with in diagnosis

Answer 10

clinical history and findings on physical examination

Question 11

define polycythaemia

Answer 11

too many RBC’s-increased Hb+Hct

Question 12

what is pseudo polycythaemia

Answer 12

reduced plasma volume

Question 13

what is true polycythaemia

Answer 13

increase in total volume of red cells in circulation

Question 14

give 4 causes of true polycythaemia

Answer 14

.blood doping/transfusion
Appropriately increased erythropoietin
inappropriate increase in erythropoietin (use/synthesis)
independent of erythropoietin

Question 15

give an example of appropriate erythropoietin increase

Answer 15

hypoxia

Question 16

what causes cyanosis

Answer 16

hypoxia

Question 17

what is cyanosis

Answer 17

blue lips/skin due to hypoxia

Question 18

give an example of inappropriate SYNTHESIS of erythropoietin

Answer 18

kidney (renal) inappropriately secretes erythropoietin

Question 19

give an example of inappropriate USAGE of erythropoietin

Answer 19

doping for a sport match

Question 20

give an example of true polycythaemia caused by a factor independent to erythropoietin

Answer 20

myeloproliferative disorders

Question 21

give a consequence of polycythaemia

Answer 21

.hyperviscosity (thick blood)

.vascular obstruction—>venous/atrial thrombosis

Question 22

how can the effects of polycythaemia be mitigated?

Answer 22

.venesection to reduce blood viscosity (remove blood)

.drugs to reduce bone marrow production of red cells

Question 23

define anaemia

Answer 23

reduction of the amount of haemoglobin in a given volume of blood (RBC+hct usually also reduced)

Question 24

give the formula for MCV

Answer 24

MCV(fl)=Hct(l/l)x1000/RBC (x10^-12)/l)

Question 25

how is MCV found in the modern era

Answer 25

indirectly by light scattering or interruption of an electric field

Question 26

causes of macrocytosis

Answer 26

lack of vitamin B12/folic acid (megoblastic anaemia)
ethanol toxicity/liver disease
haemolysis (polychromasia)
pregnancy

Question 27

causes of microcytosis

Answer 27

. deficiency in haem synthesis—>iron deficiency

.deficiency in globin synthesis

Question 28

what term is used to indicate defect in alpha chain globin synthesis

Answer 28

alpha thalassaemia

Question 29

what term is used to indicate defect in beta chain globin synthesis

Answer 29

beta thalassaemia

Question 30

give the formula for mean cell haemoglobin (MCH)

Answer 30

MCH(pg)=Hb(g/l)/RBC(x10^-12)

Question 31

give the formula for MCHC

Answer 31

MCHC(g/l)=Hb(g/l)/Hct(l/l)

Question 32

what is the difference between MCH and MCHC

Answer 32

MCH—>ABSOLUTE AMOUNT of hb in a RBC

MCHC—>CONCENTRATION of hb in a RBC

Question 33

true or false:MCH is related to the shape of the cell

Answer 33

false: MCHC is related to the shape of the cell

Question 34

true or false: MCHC is the average amount of hb in an individual cell

Answer 34

false: MCH is the average amount of hb in an individual cell

Question 35

true or false: REDUCED MCH AND MCHC is due to iron deficiency

Answer 35

true: REDUCED MCH AND MCHC is due to iron deficiency

Question 36

true or false: Reduce MCH and normal MCHC is due to thalassaemia trait

Answer 36

true:Reduce MCH and normal MCHC is due to thalassaemia trait

Question 37

true or false: Reduced MCHC but normal MCH is due to thalassaemia trait

Answer 37

false:Reduce MCH and normal MCHC is due to thalassaemia trait

Question 38

What Hb electrophoresis is observed due to iron deficiency

Answer 38

normal activity

Question 39

choose the best answer:
a) Hb A2 raised in electrophoresis due to Beta and Alpha Thalassemia trait

b) Hb A2 raised in electrophoresis due to Beta thalassemia trait
c) Hb A2 raised in electrophoresis due to alpha thalassemia trait
d) Hb A2 is raised in electrophoresis due to iron deficiency

Answer 39

b) Hb A2 raised in electrophoresis due to Beta thalassemia trait

Question 40

give 2 reasons why it is important to distinguish between iron deficiency and thalassaemia trait?

Answer 40

1) to replace iron when deficient and not incorrectly give iron supplements which won’t have effect on thalassaemia trait
2) To advice people with thalassaemia trait on potential risks to future offspring (genetic counselling)

Question 41

what further test may distinguish between thalassaemia trait and iron deficiency

Answer 41

iron studies e.g serum ferritin