week 1B Flashcards
what is macrocytosis
enlarged RBCs
what is macrocyclic anaemia
anaemia where RBCs are bigger than normal
MCV
mean corpuscular volume
MCV unit
femtolitres (fl)
MCV measures what and why
measures mean RBC volume, tell sis if its macro, normo or micro anaemia
what is a normal MCV of a RBC
80-100 fl
on blood film how can you tell if there is macrocyclic anaemia
there will be lymphocytes on film, if RBC is bigger than lymphocyte nucleus there is macro. also see paler RBCs
in amcrocytic anaemia what might FBC show
low Hb
low RBC
low HCT
high MCV
2 true causes of microcytosis
megablastic
non-megaloblastic
stages of erythropoiesis (6)
pronormobast > early normoblast > intermediate normoblast > late normoblast > reticlocyte > erythrocyte
at what stage of erythropoiesis does the cell begin to enucleate
between late normoblast and reticulocyte
at what stage of erythropoiesis do RBC start to appear in blood
reticulocyte
what does megaloblastic mean
an abnormally large nucleated RBC precursor with an immature nucleus
megaloblastic anaemia is characterised by what
defect in DNA synthesis and nuclear maturation with preservation of RNA and haemoglobin synthesis
why are RBCs bigger in megablastic anaemia
cytoplasm develops as normal (get big enough to divide) but nucleus is still immature. CELL FAILS TO BECOME SMALLER
macrocytosis id when HCV is >____fl
> 100 fl
Causes of megaloblastic anaemia
B12 deficiency
Folate deficiency
drugs
rare inherited shit
why do B12 an folate deficiency cause megaloblastic anaemia
enable chemical reactions that provide nucleosides for DNA
cycle that uses B12
methionine cycle
cycle that uses folate
folate cycle
2 important biochemical pathways that interact and use B12 and folate
methionine cycle (B12) folate cycle
why must stomach be acidic for b12 absorption
removes colbamine (B12) from animal protein
what is secreted in stomach that is needed for B12 absorption
intrinsic factor
what things can reduce intrinsic factor in stomach
pernicious anaemia
gastric atrophy
gastric bypass
B12 absorption pathway
in meat > cleaved from meat by acids > binds haptocorin > moves to duodenum > pancreatic juices cleve off haptocorin . binds intrinsic factor > moves to terminal ileum where cubulin cleaves of intrinsic factor and B12 absorbed
things that can affect B12 in duodenum
chronic pancreatitis
things that can affect B12 in small bowel
coeliacs, crohns, resection, bacterial over growth
folate is converted into
mono glutamate
where is folate (monoglutomate) absorbed
jejunum and duodenum
sources of B12
animal
sources of folate
leafy veg, yeast
body stores of B12 last how long
2-4 years
body stores of folate last how long
4 months
daily requirements of B12
1-3ug/day
daily requirements of folate
100ug/day
why is inadequate folate intake more likely than B12
lesser stores
what can cause malabsorption of folate
coeliacs and crohns
features of B12/folate deficiency
anaemia
weight loss, diarrhoea, infertility, sore tongue, jaundice
feature of B12 deficiency alone
neurological problems
what is pernicious anaemia
autoimmune resulting in destruction of gastric parietal cells
what will pernicious anaemia blood film show
- microcytic anemia
- blood film will show hyperhsegmented neutrophils (normally 3-5, so >5) megaloblastic
what lab tests can you do for pernicious anaemia
- assay B12 and folate (can be wrong)
- check for auto-antibodies against gastric parietal cells) and anti-intrinsic factor
how do you treat megaloblastic anaemia
- treat cause
- give vit B12 injections (for life in pernicious anaemia)
- folic acid tablets (5mg day)
- transfusion if life-threatening anaemia
dose of folate you give
5mg day orally
type of B12 given IV
hydroxycobalamin
2 cause categories of macrocytosis are:
genuine or spurious
what can cause spurious macrocytosis
1) reticulosis: marrow response to acute bleeding or haemolysis
2) cold-agglutinin disease: RBCs agglutinate, analyser registers this as a single large RBC
what things can you measure for anaemia
haemoglobin concentration
haematocrit
normal Hb for man
Hb 130g/L
normal Hb female
Hb 120g/L
normal haematocrit for man
Hct 0.38 - 0.52
normal haematocrit for woman
Hct 0.37 - 0.47
what cell ‘nurses’ erythroid precursors
central nursing histiocyte
how is Hb measured
lyse RBCs, and measure optical density, measure OD proportional to concentration (beer’s law)
how do you measure haematocrit
as a proportion of settles blood sample
when is Htc and Hb not good measures of anaemia
if rapid blood loss, can lose half volume of blood but sample will still appear normal….until you give fluids that will then dilute down remaining BRCs
or if you give fluids which then increase volume and cause dilution
what is reticulocytosis
high number of reticulocytes in blood due to large RBc production in response to haemolytic anaemia or blood loss
what do kindeys sense to then cause EPO release
reduced oxygen carrying capacity
what will reticulocytes have visible in them, what is this called, and how will it change appearance
RNA remnants, called polychromasia, cells will have blue/gray appearance
MCH
mean cell hemoglobin concentration
normal HCV values
80 - 96
