True statement about Antistreptolysin ‘0’ titre is ?
The question is asking for a true statement about the ASO titre. The correct answer would likely relate to its clinical use or interpretation. Let me think about the options. Since the options aren't provided, I'll have to infer common distractors. Common incorrect options might include things like ASO being used for other pathogens, or confusion with other streptococcal tests like anti-DNase B.
The correct answer is probably that a rising ASO titre indicates a recent infection. I need to explain why that's right. ASO antibodies take a few weeks to develop, so a single elevated titre isn't enough; a fourfold increase in titers over time is significant. Also, ASO isn't effective for diagnosing acute infections because it lags behind clinical symptoms and PCR methods are faster.
Now, the wrong options: One might say ASO is used for diagnosing acute infection (wrong because it's delayed). Another could claim it's a direct test for streptococci (no, it's an antibody test). Another might mix it up with other tests like ASLO (but ASO is the same as ASLO). Also, maybe an option about ASO being useful in all streptococcal infections (but it's specific to Group A).
Clinical pearls: Remember that ASO is useful for recent infections but not for immediate diagnosis. It's part of the Jones criteria for rheumatic fever. Also, ASO levels peak in 3-5 weeks and decline over months.
Putting it all together, the correct answer should state that a rising ASO titre is diagnostic of a recent Group A Streptococcus infection. The explanation needs to highlight the delay in antibody response and compare it with other tests. Each wrong option should be addressed with why it's incorrect, like not being a direct test, not used for acute cases, etc. The clinical pearl reinforces the time lag and its use in specific conditions.
**Core Concept**
Antistreptolysin O (ASO) titre measures IgG antibodies against streptolysin O, a hemolysin produced by *Streptococcus pyogenes* (Group A Streptococcus). It is used to detect **recent or past streptococcal infections**, particularly in conditions like acute rheumatic fever or post-streptococcal glomerulonephritis. The titre rises **2–3 weeks post-infection** and declines over months.
**Why the Correct Answer is Right**
A true statement about ASO titre is that it reflects **recent streptococcal infection**. The antibody response lags clinical symptoms, making it **diagnostically delayed** compared to rapid antigen detection tests. A **fourfold increase in titre between acute and convalescent samples** is confirmatory. ASO