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Flashcards in B 12 Deck (25):
1

Holotranscobalamin - what is

Transcobolamin bound to b12
Active
25% b12

2

What is haptocorrin

Glycoproteins binds 75% b12
Holohaptocorrin

3

What Changes total B 12

Change in binding protein

4

Metabolic function of b12

Last step in fatty acid digestion-
2 methylmalonyl A to succinyl co A
If this doesn’t happen in mitochondria- mma leaks out
2- making methionine w homocysteine- this will also be elevated in folate def

5

Genetic haptocorrin def

Low total b12 bug normal tissue b12(Holo TC)
No clinical manifestation b12
Found in 15% w low total b12

6

Clinical indications for b12 testing

Macrocytic anaemia
Anaemia of chronic kidney diseases
Cognitive de
Dementia
Polyneuropathy
Chronic fatigue syndrome

7

What is good negative predictor of b12 def

Normal mma/homocysteine

8

Plasma homocysteine limitations

Non fasting
Ageing/rénal impairment
Smoking, coffee wine
Low folate/Vit B6
Hyper proliferation d/o
Genetic defect

High npv

9

Mla limitations

Elderly
Rénal failure
Urine mma more influenced by good than plasma
Hypocolaemia

10

Anti if ab

Near 100% spec for PA
50-70% sens

11

Transferrin sat < 15%

Latent iron deficiency

12

Timing iron studies

Early am fast
Because dietary iron can inc iron- this is used in calculation of t sat gives false result

13

sTFr in fe def

Increased
Not affected by infection

14

sTFr in pgy

Increased due to inc stimulation of eryhtropoeisis and inc iron requirements by iron dependant cell proliferation
Can be used in pgy
Not affected by post partum inflammation like ferritin
Useful I'm unclear situations in pgy

15

McV in pgy

Falsely high due to inc erythropoeisis so not reliable for fe def

16

TIBC in pgy

Raised

17

What can lower tibc

Infl
Chronic infxn
Malignancy
Liver disease
Nephrotic syndrome
Malnutrition

18

sTFr

86% sen 75% spec
Not standardised
Is a truncated fragment of membrane receptor

19

Hepcidin in iron homeostasis

Inhibits iron entry into plasma from gut, macrophages
Deficiency causes iron overload
Interacts w ferroportin to control iron flow- causes it to internalise and degrade

20

Iron excess causes ? Hepcidin

Inc production

21

Iron

Colorimetric assay
Ferrizyme binds to iron and get colour change

22

False high iron

Haemolysis

23

Transferrin assay

Immunoturbidometric
Human t ferrin forms precipitate w antiserum which is determined turbidemetrically
Measure might- more précipitante there is less light so inv proportional to ferritin

24

Interférence w ferritin

High level paraprotein
Biotin

25

Ferritin assay

Colourimetric sandwich assay
Solid phase