This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chronic Kidney Disease & Diabetic Nephropathy, Subject name: Medicine
[{'content': 'Which is not a variable of MDRD (Modification of Diet in Renal Disease) formula? \nSelect and explain. \nA. Age, B. Gender, C. Race, D. Weight', 'role': 'user'}, {'content': 'Answer: D \nExplanation: TEST : 1. CKD - EPI - cystatin C method (BEST) ; Cystatin - C is produced by nucleated cells 2. Modification of diet in renal disease formula GFR= 186.3 x (serum creatinine level ( mg/dl))-1.154 x age-0.203 x ( 0.742 if female ) x (1.21 if black) 3. Cockroft Gault formula 4. Creatinine clearance 5. Inulin clearance', 'role': 'assistant'}]