A chart to aid in the interpretation of iron studies. These are set of blood tests which may include ferritin, serum iron, transferrin, transferrin saturation and TIBC.
Means ferric ions Fe3+ bound to serum transferrin Only 0.1 % of total body iron is bound to transferrin at any one time Little value if tested on its own as levels may fluctuate through the day. Serum iron would be decreased in Genuine iron deficiency Inadequate Fe absorption Chronic blood loss Pregnancy 3 rd trimester Chronic illnesses like SLE , Rh arthritis.
Serum iron increased in – Haemolysis Iron overdose Lead toxicity Hepatic necrosis Haemochromatosis
Major iron binding protein – carries iron from the liver to the bone marrow A beta globulin which is also an acute phase protein Synthesized in liver and regulates iron absorption Transferrin increases in iron deficiency to maximise the utilsation of available iron Also known as siderophilin
Transferrin reduced in chronic infections microcytic anaemia as a result of chronic diseases protein deficiency liver damage haemochromatosis kidney injury – loss of transferrin in urine malignancy atransferrinemia – genetic mutation
Transferrin elevated in Iron deficiency anaemia Pregnancy
Percentage of transferrin and other iron binding proteins Helps find the cause of abnormal iron and TIBC levels Typically transferrin is 30 % saturated with iron Transferrin saturation rises in iron overload and falls in iron deficiency A rise in serum iron due to dietary iron intake can cause raised transferrin saturation. Transferrin saturation reduced in Iron deficiency anaemia Anaemia of chronic disease Acute phase response.
Transferrin saturation elevated in haemolytic anaemia sideroblastic anaemia megaloblastic anaemia patient with iron overload or iron intoxication Haemochromatosis
Total iron binding capacity (TIBG)
Indicates the availability of iron binding sites on transferrin It is an indirect measure of transferrin concentration It is the sum of all the protein bound to iron TIBC would be elevated in 70 % of of patients with Fe deficiency anaemia. It is reduced in Haemochromatosis Hypoproteinaemia in malabsorption Burns Cirrhosis Renal disease Thalassemia Hyperthyroidism Non-iron deficiency anaemia.
TIBC elevated in Pregnancy Iron deficiency Acute hepatitis Acute and chronic blood loss.
Isolated elevated transferrin saturation- repeat a fasting sample. If consistently raised consider HFE gene analysis with pre-test counseling
Acute hepatic injury can present as raised iron , transferrin ,transferrin saturation and ferritin . This is due to leakage of hepatic content and can be easily confused with iron overload
- Interpreting iron studies BMJ 2017;357:j2513 ( 2017 , June 15)
- Melbourne haematology A guide to the interpretation of iron studies – Overview
- Deranged Physiology Interpretation of iron studies via www.derangedphysiology.com
- Ogun AS, Adeyinka A. Biochemistry, Transferrin. [Updated 2019 Jan 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019
- TIBC , Transferrin and Transferrin saturation from www.labpedia.net
- www.Irondisorders.org- How do I know if I am anaemic