Lecture 21 Flashcards
Biochemical assessment of iron status II
Issues of Iron overload
- acute iron toxicity
- hereditary haemochromatosis
- african iron overload
- other iron overload conditions
hereditary haemochromatosis is a what condition
autosomal recessive condition
you have poor control of what when you have hereditary haemochromatosis
poor control of iron absorption
what happens in hereditary haemochromatosis
iron accumulates in liver, pancreeas and heart muscle which impacts their function
When should effective treatment start for hereditary haemochromatosis
treatment is very effective if started early
what are the biochemical indices that would indicate hereditary haemochromatosis (serum ferritin and transferrin saturation)
serum ferritin :
>300ug/L males
>200ug/L females
transferrin saturation :
>45% men and women
repeated in a fasting sample
Clinical assessment
a medical history and a physical examination are the clinical methods used to detect signs, (observations made by a qualified examiner) and symptoms (manifestations reported by the patient) associated with malnutrition
clinical assessment has to be done alongside …… why ?
alongside other measures of nutritional assessment because otherwise someone could be diagnosed as something that they don’t have
what are the individual level uses of iron status indicators
- screening
- clinical assessment
when looking at an individuals iron status that is close to but not below the cut offs what usually happens and how is that different to population status
they will usually be treated with iron medication, different to population level were cut offs are strictly used
population level uses of iron status indicators
- prevalence estimates of deficiency
- planning appropriate interventions
- evaluating impact of interventions
what is the context of individual assessment of Fe status
- availability of assay
- usefulness
- cost
what are the indices of individual assessment of Fe status
- haemoglobin
serum ferritin and C-reactive protein ?
serum Fe, transferrin saturation = if concerned about possibility of iron overload
what type of index data is most useful in population practice
combining indices to look at things such as iron deficiency anaemia etc, instead of things such as low haemoglobin
what are the factors affecting validity of cut offs
- method of blood collection
- fasting status / time of day
- assay / equipment used
- infection (inflammation)
- environment and other confounding factors
- genetics
what does fasting status / time of day affect validity of cut offs for iron
very highly changeable depending on the time of the day
transferrin saturation changes over the day, usually high in the morning and then decreases throughout the day
Inflammation what happens
-phase response to inflammation, infection and malignancy
- blocks the release of Fe from reticuloendothelial system
- increases translation of ferritin
- leads to shortage of Fe in bone marrow
when inflammation is present why does your body try store iron and remove it from circulation
because bacteria need iron in order to grow so your body doesn’t want iron to be where bacteria is
Iron indices and infection: Measure of infection
C-reactive protein
a-1-acid glycoprotein
a-1-antichymotrypsin
what are other sources of variation in iron indices
- oral contraceptive agents (decrease transferrin saturation)
- smoking (increases haemoglobin)
- altitude (increases haemoglobin)
- “sports anaemia” (decreases haemoglobin)
- dehydration (increases indices)
what is the main cause of anaemia
iron deficiency
anaemia can also be caused by
- infection (malaria, HIV)
- decreased erythropoiesis (bone marrow depression, B12 or folate deficiency)
- genetic disorders (thalassemia, sickle cell anaemia)
thalassemia presents
abnormal cell shapes
Microcytic blood cells
If you don’t have enough iron to make enough HB then you are going to have small cells
Mesoblastic blood cells
If a cell cant dividf when being formed then they are still going to have their nucleus apart of them they are much larger and there are less of them and it decreases the amount hemoglobin
if someone has
low haemoglobin,
normal mean cell volume,
low - norm transferrin saturation,
high-norm ZPP
high ferritin
what do they likely have
chronic disease
The cells you’ve got are fewer but they are normal
if someone has
low haemoglobin,
high mean cell volume,
high-norm transferrin saturation,
normal ZPP
normal ferritin
what do they likely have
macrocytic anaemia
These are big cells and iiron isnt the problem its make the RBC that is the problem
if someone has
low haemoglobin,
low mean cell volume,
high transferrin saturation, norm ZPP
norm ferritin
what do they likely have
thalassemia
Less heam and smaller cells
Low everything but high ZPP
IDA
the use of haemoglobin results alone is an
overestimate of prevalence of IDA
