Which laboratory value is used to measure iron availability for ESA therapy?

• A. TSAT And Ferritin
• B. Sodium And Potassium
• C. Creatinine And BUN
• D. Vitamin D And Phosphate

Answer: (A)

Iron availability for ESA therapy is judged by looking at how much iron is circulating and how much iron is stored. Transferrin saturation (TSAT) shows the portion of transferrin bound with iron, reflecting the iron that’s immediately available for red blood cell production. Ferritin indicates the amount of stored iron. Together, TSAT and ferritin give a complete picture of iron status: enough circulating iron to support erythropoiesis and sufficient iron reserves so therapy isn’t blocked by iron deficiency. If iron is insufficient, ESA therapy won’t work well and iron supplementation is needed. The other lab pairs relate to different bodily systems—electrolyte balance (sodium/potassium), kidney function (creatinine/BUN), or bone-mineral metabolism (vitamin D/phosphate)—and do not measure iron availability for ESA.