![]() ![]() Problems in interpretation of serum transferrin levels in relation to body iron stores – Concurrent acute or chronic inflammation – Recent iron medication, possibly unappreciated as a component in vitamins with mineral supplements Problems in interpretation of serum iron levels in relation to body iron stores Estimation of serum iron alone in the investigation of anaemia is consequently inadvisable. Unfortunately, a low serum iron level in this setting is frequently misinterpreted as evidence of iron deficiency, a major diagnostic error that can be avoided by simultaneous examination of the transferrin level, which in this context is subnormal or in the low normal range. The effect on iron and transferrin levels persists as long as the inflammatory process is sustained, and is classically associated with the development of anaemia of chronic disease. This response can produce a marked decrease within a day, especially in the serum iron level. The concentrations of iron and transferrin in the serum are significantly affected, and fall rapidly as part of the acute phase response after the onset of the inflammation irrespective of the status of the iron stores in the body. The diagnostic specificity of a low serum iron for iron deficiency is lost in the presence of inflammatory processes and certain other forms of chronic disease (Tables 2 and 3). A subnormal level of iron in association with a supranormal level of transferrin is very strong evidence of iron deficiency (Table 1). The concentration of transferrin rises under these circumstances towards, or above, the upper limit of the normal range. The serum (or plasma) iron concentration falls progressively below the normal range (14-32 micromol/L) when the amount of iron in the body decreases after the reserves of iron have become exhausted. Endoscopy is appropriate only if there is evidence of iron deficiency not explained by other causes, or highly suggestive clinical indications of gastrointestinal disease. However, currently available tests provide a reliable index of iron status sufficiently frequently that it is not appropriate to perform endoscopic examinations merely because a patient has anaemia, especially normocytic anaemia. This gives a more reliable overview of the situation than is provided by any individual test. The impact of these factors can be recognised by combining the results of currently available tests. This is important to recognise as such distorted results may give a misleading view of the patient's iron stores. The results of tests of iron status are relatively frequently distorted by other clinical factors. It can also occur in some patients with anaemia secondary to chronic infection, inflammation, or malignancy (anaemia of chronic disease), even though the majority of these patients have a normal mean corpuscular volume (MCV). Microcytic anaemia is most commonly due to iron deficiency, but is also caused by thalassaemia. In my practice, I look for iron deficiency and interpret iron overload as indicative of inflammation.-and, less commonly, in cases of first relatives diagnosed with haemachromatosis.Biochemical tests for iron deficiency help to evaluate the cause of microcytic anaemia (a mean red cell corpuscular volume Levels 100 ug/l generally excludes iron deficiency Is now well established in assessment of iron stores, Normal range 15 – 300 ug/l (reference ranges vary depending on the method used). Serum ferritin: Small amount of circulating serum ferritin reflects body iron stores. The level of transferrin saturation is particularly helpful if assessment of early stages of iron overload with levels > 55% for males and > 50% for females indicative of iron overload (should be fasting level for more accurate assessment) (In my practice, I use this to have extra evidence of inflammation. Transferrin levels are reduced in inflammation. Total iron binding capacity (TIBC) is a direct measure of level of transferrin. ![]() Iron is bound to transferrin in the plasma. Serum transferrin (or total iron binding capacity TIBC) / Transferrin saturation. Serum iron Considerable variation occurs within a day in individuals and assessment of serum iron alone provides little helpful clinical information. If initial serum iron is low I repeat the test to identify if low serum iron is a chronic or long standing event. The following figures on Iron Studies are taken from Melbourne haematology guidelines. Iron studies require detailed interpretation. ![]()
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