Iron Metabolism
Iron Metabolism Plot according to Thomas
The conventional biochemical markers for iron metabolism - ferritin, transferrin, and transferrin saturation - provide insufficient results for differential diagnostics of iron deficiency in context with anaemia caused by chronic diseases and during erythropoetin therapy.
One good option to close this diagnostic gap is offered by the ferritin index as an indicator of the iron supply for erythropoiesis in combination with reticulocyte haemoglobin (Ret-He) that is lowered in case of functional iron deficiency.
The graphic depiction in the "diagnostic diagram" according to Thomas et al. (the so-called "Thomas Plot") allows for a differential diagnosis that distinguishes between stored iron and functional iron deficiencies and provides evidence for adequate therapy at the same time.
Since the ferritin index, that is calculated as the quotient of the soluble transferrin receptor (sTfR) divided by the logarithm of ferritin (log Ferritin), is influenced by inflammatory reactions (CRP >0.50 mg/dl), this parameter is included in the construction of the plot.
- Thomas L, Thomas C, Heimpel H Neue Parameter zur Diagnostik von Eisenmangelzuständen. Dtsch Arztebl 2005; 102:A 580–586
- Thomas C, Thomas L Biochemical Markers and Hematologic Indices in the Diagnosis of Functional Iron Deficiency. Clin Chem 2002; 48:7 1066–76
- Thomas L, Thomas C, Heimpel H Neue Parameter zur Diagnostik von Eisenmangelzuständen. Dtsch Arztebl 2005; 102:A 580–586
- Thomas C, Thomas L Biochemical Markers and Hematologic Indices in the Diagnosis of Functional Iron Deficiency. Clin Chem 2002; 48:7 1066–76