This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
Estimation of S. Ca2+ should be done only after- 
Select and explain. 
A. Urine calcium, B. Total plasma protein, C. S. Phosphate, D. S.K+
C: S. Phosphate
Answer: C: S. Phosphate 
Explanation: Ans is options 2 and 3 Factors affecting serum Calcium are Amount of protein present in blood pH of blood Ref Ganong 21/e p385