A 7-year-old boy develops periorbital oedema and haematuria two weeks after treated impetigo. Urine shows red cells and casts. His ASO titre is within normal limits. Which test would be MOST appropriate to demonstrate preceding streptococcal infection in this setting?

• A Repeat ASO titre on convalescent serum only
• B Anti-streptozyme panel for rheumatic fever follow-up
• C Throat swab culture
• D Anti-DNase B titre ✓

Explanation

After streptococcal pyoderma, ASO titres are often low or absent because skin lipids inhibit the immune response to streptolysin O. Anti-DNase D rises reliably after both pharyngeal and cutaneous streptococcal infection and persists longer, making it the preferred test for confirming antecedent streptococcal skin infection in post-streptococcal glomerulonephritis. Throat cultures are usually negative by this stage since the infection was cutaneous.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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