This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
Antistreptolysin O test is diagnostic in 
Select and explain. 
A. Acute rheumatic fever, B. SLE, C. SBE, D. Rhematoid ahritis
A: Acute rheumatic fever
Answer: A: Acute rheumatic fever 
Explanation: In rheumatic fever, a retrospective diagnosis of streptococcal infection may be established by demonstrating a high level of antibody to the streptococcal toxin. The standard test is Antistreptolysin O titration: ASO titer higher than 200 is indicative of prior streptococcal infection. Usually, high levels are found in acute rheumatic fever but in glomerulonephritis, titers are often low. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 218