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: Medicine
A lady presents with complaints of abdominla pain. CECT shows bilateral papillary necrosis. Which of the following test shall not be done to investigate the cause of her papillary necrosis? 
Select and explain. 
A. Urine acidification test, B. Sickling test, C. Urine -PCR for TB, D. Bacterial culture of urine
A: Urine acidification test
Answer: A: Urine acidification test 
Explanation: Ans. a. Urine acidification test(Ref: Harrison 19/e p1860, 18/e p2372)Urine acidification test is mainly done to diagnose A (Renal tubular acidosis), not the causes of papillary necrosis.