This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urology, Subject name: Surgery
A boy is suffering from acute pyelonephritis. Most specific urinary finnding will be: 
Select and explain. 
A. WBC cast, B. Leucocyte esterase test, C. Nitrite test, D. Bacteria in Gram stain
C: Nitrite test
Answer: C: Nitrite test 
Explanation: Sensitivity and Specificity of Urinanalysis in UTI: Tests Sensitivity (%) Specificity (%) Esterase 83 (67-94) 78(64-92) Nitrite 53(15-82) 98(90-100) Esterase or NItrite 93(90-100) 72(58-91) White blood cells 73(32-100) 81(45-98) Bacteria 81(16-99) 83(11-100) Any above 99.8 (99-100) 70(60-92) Ref: Smith 18th edition Pgno: 200