Streptococcal antibodies (aso)
Microbiology
Notes
- This investigation comprises two tests: anti-streptolysin O antibodies (ASO) and streptococcal anti-DNase B (ADB) antibodies
- Guidance on interpretation can be found at the Public Health England website.
ASO antibodies
- Streptolysin O is produced by almost all strains of S.pyogenes (group A streptococci) and many group C and group G beta haemolytic streptococci
- May be used for diagnosis of recent streptococcal infections such as pharyngitis and tonsillitis but is unable to distinguish between infections with groups A, C and G streptococci. At best 80% of cases have positive ASO serology. The preferred method for acute sore throat is a bacterial throat swab for culture and sensitivity.
- Useful for acute rheumatic fever, 80% positivity
- Not very useful for infections such as impetigo and pyoderma
- False positives may occur in jaundiced patients with liver disease
- ASO rises 1 week after infection and peaks within 3-5 weeks returning to normal after 6-12 months
ADB antibodies
- DNase B is produced by group A streptococci and is therefore more specific than the ASO antibody test
- May be used to diagnose skin infections as well as pharyngitis. However, the preferred diagnostic method is a bacterial swab for culture and sensitivity.
- ADB titres peak later than ASO and may remain elevated for several months: therefore may be useful for after the event diagnoses e.g. Sydenham's chorea, but may be negative in recent/current infection
- >90% of patients with pyoderma, acute post streptococcal glomerulonephritis, acute rheumatic fever or other post streptococcal sequelae will have positive ADB antibodies
Sample requirements
Serum - paired samples not normally required
8.5ml of blood taken into a plain gel tube
Required information
- Relevant clinical details
- Date of onset
Storage/transport
Store at fridge temperature
Transport as soon as possible at ambient temperature
Turnaround time
Up to 8 days