This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Interstitial fluid volume can be determined by: 
Select and explain. 
A. Radioactive iodine and radiolabelled water, B. Radioactive water and radiolabelled albumin, C. Radioactive sodium and radioactive water, D. Radioactive sodium and radioactive labelled albumin
D: Radioactive sodium and radioactive labelled albumin
Answer: D: Radioactive sodium and radioactive labelled albumin 
Explanation: Ans: D. Radioactive sodium and radioactive labelled albumin(Ref Ganong 25/e p3, 24/e p2; Guvton I p309, 310)Fluid volumeIndicator usedTotal body water volumeDeuterium oxide: D20 (MC used)degTritium oxidedeg, Aminopyrinedeg, AntipyrinedegExtracellular fluid volumeInulin (most accurate)degs22Na, 1251-iothalamate, thiosulfatedegPlasma volumeEvans bluedegSerum albumin labeled with radioactive iodinedeg (1-125)Intracellular fluid(Calculated as total body water - extracellular fluid volume)Blood volume"Cr-labeled RBCsdeg, or calculated as blood volume = plasma volume/ (1 - hematocrit)Interstitial fluid(Calculated as extracellular fluid volume - plasma volume)