Streptococcal antibodies

Microbiology

Notes

 Gram stain of Streptococcus pyogenes

  • 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. link to an external site

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 

8.5mL BD Vacutainer 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


Page last reviewed: 15/10/2013