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: Microbiology
Anti streptolysin 0 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: Ans. is 'a' i.e., Acute rheumatic fever . ASO titres higher than 200 are indicative of prior streptococcal infection. High levels are usually found in acute rheumatic fever.