- Take blood (3 to 5 mL) to prepare the serum.
- The early morning sample is preferred because of the diurnal variation in the iron concentration.
- Take the sample in the morning (around 10 am) because the level of iron varies during the day.
- The specimen may be collected as serum without anticoagulant.
- Can use plasma with heparin.
- Reject the hemolysed sample.
- Do not use anticoagulant like oxalate, citrate, or EDTA, because these binds iron, so are unacceptable.
- 12 hours fasting is preferred.
- Water intake is allowed.
- Stop taking the iron-containing supplements before 24 to 48 hours.
Purpose of the test
- This is done to diagnose the anemias.
- Others test needed are Total iron and Transferrin.
- This helps in iron metabolism.
- Iron is a most abundant trace element in the body.
- 65% is bound to Heme.
- Measurement of the iron concentration refers specifically to the Fe +++ bound to the transferrin and not to the iron circulating as free hemoglobin in the blood.
- Iron is constituents of:
- Several enzymes.
- Iron in the food is absorbed by the intestinal epithelium.
- Iron is ingested as Fe +++ form and is converted to Fe ++ form for the absorption.
- The conversion of Fe +++ to Fe ++ form takes place in the stomach where gastric acid HCL provides the acidity to reduce the iron.
- Ferric (Fe+++) iron is reduced to Ferrous (Fe++) by vit.C and this ferrous form is absorbed very easily.
- Milk and antacid bind iron and reduce its absorption.
- Iron 1 mg/day is lost in the urine, sweat, bile and epithelial cells.
- In the blood, this absorbed iron attaches with the transport protein (Transferrin).
- So transferrin may indirectly represent the TIBC.
- Ferritin represents stored iron.
- 10 to 20% to 30% of the total iron is stored as Ferritin.
- Iron is stored as ferritin in the body in liver, spleen and bone marrow.
- Or stored as Ferric (Fe +++) bound to an apoferritin protein molecule.
- When iron is needed then it is released from the Ferritin and is then bound to β1 globulin molecule, transferrin.
- Serum Ferritin is the best diagnostic test for the iron deficiency anemia.
- Because ferritin is the measure of the iron stores in the body.
- In an iron deficiency anemia, the ferritin level is <15 µg/L as compared to the normal level of 20 to 250 µg/L.
- In children <6 µg/L compared to the normal value of 7 to140 µg/L.
- In baby <12 µg/L compared to the normal values of 50 to 200 µg/L.
- Ferritin is the acute phase protein, so its value may increase in infections, SLE, liver diseases, malignancies, and chronic renal failure.
- Transferrin represents the major protein which binds to iron. Majority of the iron is bound to transferrin.
- Transferrin is a beta-globulin (β1-globulin).
- Transferrin capacity to bind iron in normal plasma is 240 to 360 µg/dL.
- Transferrin also acts as an acute phase protein.
- This is a transport protein synthesized in the liver.
- This regulates iron absorption.
- Transferrin also called siderophilin.
The cellular uptake of iron is mediated by the cell surface transferrin receptor (TR).
- Total iron + TIBC + Transferrin when done together help in the differential diagnosis of anemia.
Transferrin saturation is the percentage of transferrin and other iron binding proteins.
- The number of transferrin receptors depends upon the needs of the cell for the iron.
- In the case of apoferritin deficiency, an excess of the iron is deposited as small granules as Iron-oxide, called hemosiderin.
Total iron binding capacity (TIBC) is the capacity of transferrin to bind to iron.
- Transferrin saturation is calculated as follows.
- Transferrin saturation (%) = serum iron level (µg/dL) / TIBC (µg/dL) x 100
- Normal value for transferrin saturation is 20 to 50%.
- This may vary with age and sex.
- Transferrin saturation is helpful to find the cause of abnormal iron and TIBC level.
- Transferrin saturation is decreased below 15% in a patient with iron deficiency anemia.
- Transferrin saturation is increased in patients:
- Hemolytic anemia.
- Sideroblastic anemia.
- Megaloblastic anemia.
- Patient with iron overload or iron poisoning.
- TIBC is an indirect measurement of Transferrin concentration.
- TIBC measure the total amount of iron that apotransferrin has the capacity to bind.
- TIBC refer to the amount of iron that could be bound by saturation of transferrin and other minor iron-binding proteins present in the serum or plasma.
- TIBC is the sum of all protein bound to iron.
- TIBC increases in 70% of the patients with iron deficiency anemia.
- When serum iron falls then TIBC increases.
- TIBC is increased in the presence of iron deficiency but may be normal or low in chronic diseases.
- TIBC may be calculated from the direct measurement of serum transferrin by the following formula:
- TIBC µg/dL = serum transferrin mg/dL x 1.2521.
- A small proportion of the iron is bound to other proteins, so the above equation underestimates the TIBC.
- The unsaturated iron-binding capacity, the amount of apotransferrin is still available to bind the iron, can be measured.
|0 to 4 days
||130 to 275
|3 months to 16 years
||203 to 360
|16 to 60 years
||215 to 365
||250 to 380
|60 to 90 years
||190 to 375
||186 to 347
|Maternal at term
- To convert into SI units x 0.01 = g/L
Total Iron binding capacity (TIBC)
Iron saturation (%Transferrin saturation)
- Male = 20 to 50%
- Female = 15 to 50%
- To convert into SI units x 0.01 = Fraction saturation
- 250 to 400 µg/dL.
- It decreases in the older people around = 250 µg/dL.
- (This value varies from one reference to other)
- Adult = 250 to 425 mg/dL.
- Children = 203 to 360 mg/dL.
- Newborn = 130 to 275 mg /dL.
- Male = 20 to 50 %.
- Female = 15 to 50 %.
- Adult male = 12 to 300 ng/mL (12 to 300 µg/L).
- Adult female = 10 to 150 ng/mL (10 to 150 µg/L).
- Newborn = 25 to 200 ng/mL.
- One month old = 200 to 600 ng/mL.
- 2 to 5 months old = 50 to 200 ng/mL.
- 6 months = 7 to 142 ng/mL.
Increased TIBC is seen in:
- Iron deficiency.
- Acute hepatitis.
- Acute and chronic blood loss.
The decreased TIBC is seen in:
- Hypoproteinemia in malabsorption.
- Renal diseases like nephrosis etc.
- Chronic diseases.
- Non- iron deficiency anemia
The increased Transferrin is seen in:
- Iron deficiency anemia.
- Estrogen therapy.
The decreased Transferrin is seen in:
- chronic infections.
- Microcytic anemia due to chronic diseases.
- Protein deficiency in malabsorption and burns.
- Liver disease, acute.
- The renal disease like nephrosis.
- Genetic deficiency of transferrin.
||Decreased or Normal
- Please see more details in Total Iron.
Possible References Used
Back to tests