Group A-beta-hemolytic Streptococcus produces several virulent factors--- streptolysin o,strptolysin s,streptokinase,Dnase B,hyaluronidase A pt infected with GABHS produces antibodies vs these virulent factors--- anti-streptolysin o(ASO),anti-sterptokinse,anti-hyaluronidase,anti- Dnase B. ASO titre takes 2 weeks to rise & remain elevated for 3-6 mo.
Four fold (two tube) increase in titre demonstrated over time(2-4 weeks apart) would suggest a recent steptococcal infection. Single ASO titre >200 IU in children 5-15 yrs.
A pt with fever,migratory polyarthritis +- cardiac murmer-- -to support diag. of acute rheumatic fever. A pt with oliguria,hematuria,HTN---post-streptococcal GN. In pts suspected to have neurological syndromes driven by a previous grp A streptococcal infection such as Pediatric auto immune neuropsychiatric disorders associated with streptococcal pyogenase(PANDAS) & rheumatic chorea. In pts suspected to have other grp A streptococcal infections such as scarlet fever,neonatal sepsis & osteomyelitis.
Diag. of ARF is clinical:Jone’s criteria(1 major+2 minor or 2 major criteria with supportive evidence of streptococcal infection). Elevation of ASO titre in non-ARF conditions:1) Post-streptococcal reactive arthritis(PSRA)2) Systemic onset Juvenile idiopathic arthritis3) SLE4) Takayasu d/s5) HSP6) Periodic fever syndrome
Anti-Dnase BIn ARF : ASO +ve in 80% Anti-Dnase B +ve in 82% ASO+Anti-Dnase B +ve in 92% Streptozyme test Lacks standarization & reproducibility Not reliable Throat swab
1. Latent period shorter (1 week) in PSRA.2. Arthritis is additive in PSRA rather than migratory.3. Relatively poor response to Aspirin in PSRA.4. Arthritis persists for mean period of 2 mo in PSRA.5. 6% of PSRA may develop mitral valve d/s. It is thus recommended that anti streptococcal prophylaxis be given for 1 yr & then discontinued if there is no evidence of cardiac involvement.