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
True statement about Antistreptolysin ‘O’ titre is: 
Select and explain. 
A. In normal people the titre is <200, B. In acute glomerulonephritis the titre is low, C. ASO titre >200 indicate rheumatic fever, D. Streptozyme test is an active haemagglutination test
B: In acute glomerulonephritis the titre is low
Answer: B: In acute glomerulonephritis the titre is low 
Explanation: Retrospective Diagnosis of Streptococcal infection

ASO (Anti Streptolysin ‘O’) titre :

– Estimation of antibody aganist streptolysin is a standard serological test for retrospective diagnosis of streptococcal infection.
– ASO titre > 200 are indicative of prior streptococcal infection.
– Raised after throat infection only
– Acute rheumatic fever :
- High level of ASO titre are usually found
- Titres > 300 or 350 are taken as significant.
– Acute glomerulonephirits :
- ASO titres are often low.

Streptozyme test – Passive slide hemaglutination test

Becomes positive after nearly all types of streptococcal infection whether of throat or skin.

Anti DNA ase B and Antihyaluronidase – Useful for retrospective diagnosis of Streptococcal Pyoderma or for acute glomerulogephritis for which ASO titre is of much less value