Iron Deficiency Evaluation

Introduction to TSAT

The normal range of transferrin saturation (TSAT) in adults is between 20% and 50%, which is the accepted standard for evaluating iron status in the body, according to Clinical Nutrition guidelines 1
TSAT is a parameter that indicates the percentage of total iron-binding capacity being used, calculated by the formula: TSAT (%) = (Serum iron × 100) ÷ Total iron-binding capacity (TIBC) 1

A TSAT <20% suggests available iron deficiency for erythropoiesis, as indicated by the American Journal of Kidney Diseases 2
In patients with chronic kidney disease, a TSAT <20% along with ferritin <100 ng/mL indicates absolute iron deficiency, according to Kidney International Supplements guidelines 3
A TSAT >50% may indicate iron overload, with half of the transferrin binding sites occupied by iron, as suggested by the American Journal of Kidney Diseases 2

Inflammation can alter TSAT values, decreasing them despite adequate iron stores, as noted by Clinical Nutrition 1
Diurnal variations in serum iron can affect TSAT values, but serial measurements taken at the same time of day minimize this effect, according to the American Journal of Kidney Diseases 2
In the presence of inflammation, hepcidin may be a more accurate indicator of iron status than TSAT, as indicated by Clinical Nutrition guidelines 1

In patients on hemodialysis, it is recommended to maintain TSAT >20% to optimize response to erythropoiesis-stimulating agents, according to Kidney International Supplements guidelines 3
The American Journal of Kidney Diseases suggests that deficiencia absoluta is characterized by TSAT <20% with ferritin <100 ng/mL, while deficiencia funcional is characterized by TSAT <20% with normal or elevated ferritin (100-700 ng/mL) 2

There is no universal standardized method for determining serum iron, so reference ranges may vary depending on the laboratory, as noted by Clinical Nutrition 1
The American Journal of Kidney Diseases recommends considering the context of the patient, including other parameters such as serum ferritin, hemoglobin, and clinical context, for a complete evaluation of iron status 2