Question

Glomerulonephritis following streptococcal infection is diagnosed by which of the following tests?

• A. Blood culture
• B. Throat culture
• C. ASO titre
• D. PCR

Hint:

The organism is cleared by the time disease appears, so use a serological antibody test.

Answer 1

The Correct Option is C

Step 1: Acute glomerulonephritis after a streptococcal sore throat or skin infection is a delayed immunological reaction, so the bug itself is usually gone when the kidney disease shows up.

Step 2: Because direct isolation fails, doctors look for the immune footprint of the infection. Antibodies against streptolysin O rise after infection, and measuring this antistreptolysin O level is the standard serological proof of preceding streptococcal disease. Values over 200 units are taken as significant.

Step 3: Throat and blood cultures are typically negative this late, and PCR is not used routinely here. Note that a raised ASO titre confirms recent streptococcal infection but does not by itself prove rheumatic fever. Hence the diagnostic test is the ASO titre.\[\boxed{\text{ASO titre}}\]