Iron Deficiency Anemia Flashcards
Why IV iron used to be contraindicated
“high molecular” weight iron dextran (HMW ID) was associated with anaphylaxis and shock, including fatal events, and which has been largely removed from the market. “low molecular” weight ID is different.
Which labs respond first following iv iron
Retic –> hgb –> MCV –> ferritin
Efficacy and differences among IV iron formulations
- efficacy is similar among all of them and safety is similar, except for high molecular weight IV dextran, so it just comes down to which is on formulary.
Typical IV iron formulation used
typically low molecular weight iron dextran (low cost + can be given in single dose)
Determining dosage of IV iron
In practice, there is no evidence that total doses above 1000 mg of elemental iron are clinically useful. We often give a fixed dose of approximately 1000 mg, which is generally sufficient to treat anemia (typical red blood cell iron deficit between 500 and 1000 mg) and provide additional storage iron without causing iron overload.
% saturation calculation
(serum iron over TIBC) x 100%
Situation in which you would never want to administer IV iron
active infection
Does iron deficiency absent anemia require treatment?
Yes
What is % saturation
% transferrin saturation
How to diagnose IDA in an inflammatory state
***soluble transferrin receptor (measures level of transferrin in blood, which isn’t sensitive to inflammation)
Gold standard for IDA diagnosis
BMB – Iron stain (Prussian blue stain) of a bone marrow aspirate smear to assess iron stores in bone marrow macrophages and erythroid precursors (sideroblasts) on marrow spicules.
Indications for IV iron
1) severe, ongoing blood loss
2) intolerance (GI SE’s)
3) malabsorption syndrome (bariatric surgery, celiac’s)
4) inflammatory state
5) concern for compliance
Percent saturation reference range
15% to 50%
Transferrin saturation suggesting iron deficiency
Less than 20%
Transferrin saturation suggesting iron overload
Greater than 50%
Goal for IDA
Normal ferritin and transferrin saturation
Causes of reduced iron absorption
Celiac disease
Autoimmune gastritis
H pylori infection
What to emphasize when ferritin and transferrin saturation are discordant
Transferrin saturation
What is TIBC measuring
Transferrin but in different units
Transferrin saturation is
serum iron/TIBC
What is soluble TfR a measure of? what direction does it go in in IDA?
- Erythropoeisis/erythropoetic rate
- Increases with iron deficiency
inflammatory regulator of hepcidin
primarily IL-6
Term for iron overload from a lot of transfusions
Transfusional iron overload
Other RBC morphologies with severe IDA
“pencil” and target cells
What to remember about thinking PRBC transfusion will give patient iron
Iron is bound to heme so it will take a while to be recycled and liberated and able to be used for hematopoeisis (so they will still need iron)
when to tell patients to take iron
Slower gut transit (will improve absorption)
How to test for absorption defect
Oral iron challenge test
How oral iron challenge test is performed
- measure serum iron pre and post 2 mg/kg oral ferrous sulfate
- serum iron should increase by 50-100 mg/dL at 90 minutes
Primary issue with LMW iron dextran
You have to give test dose
Cost of IV iron
cheap these days
Which IV iron to use
Check to see what’s on formulary and become familiar with it
Inherited form of iron deficiency anemia
IRIDA – iron refractory erythrodyspoeisis
Soluble transferrin receptor is a measure of
erythropoiesis
Lab features of early iron deficiency
no or borderline anemia (this is why iron deficiency needs to be treated)
- low transferrin sat
- low ferritin
- elevated RDW
- low relic
- high soluble transferrin receptor
how long do you treat IDA for?
Duration of treatment based on iron deficit, not normalization of hgb
Caveat about thinking transfusion will replete iron
iron isn’t immediately available (will have to be recycled and liberated)
Rule of thumb for how long it takes to replete iron stores
3-6 months
How oral iron test works
- Measure serum iron pre and post 2 mg/kg oral ferrous sulfate
- should increase by 50-100 mg/dl at 90 minutes
Venofer generic name
iron sucrose
Infed generic name
iron dextran
oral iron formulation with fewer GI side effects
Ferric maltol
what is “iron saturation” on lab report
That is transferrin saturation
What is transferrin saturation
Ratio of serum iron to TIBC
Iron transport protein (from inside to outside of cell)
Ferroportin
