This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pediatrics
Investigation of choice for confirming Henoch Schonlein Purpura is 
Select and explain. 
A. Serum IgA levels, B. CRP levels, C. Renal Biopsy, D. DTPA
C: Renal Biopsy
Answer: C: Renal Biopsy 
Explanation: Biopsy of the kidney may be performed both to establish the diagnosis or to assess the severity of already suspected kidney disease. The main findings on kidney biopsy are increased cells and IgA deposition in the mesangium (pa of the glomerulus, where blood is filtered), white blood cells, and the development of crescents.(Refer: Nelson's Textbook of Pediatrics, SAE, 1st edition, pg no. 1217 - 1218)