True statement about Antistreptolysin ‘O’ titre is:

Retrospective Diagnosis of Streptococcal infection ASO (Anti Streptolysin ‘O’) titre : – Estimation of antibody aganist streptolysin is a standard serological test for retrospective diagnosis of streptococcal infection. – ASO titre > 200 are indicative of prior streptococcal infection. – Raised after throat infection only – Acute rheumatic fever : - High level of ASO titre are usually found - Titres > 300 or 350 are taken as significant. – Acute glomerulonephirits : - ASO titres are often low. Streptozyme test – Passive slide hemaglutination test Becomes positive after nearly all types of streptococcal infection whether of throat or skin. Anti DNA ase B and Antihyaluronidase – Useful for retrospective diagnosis of Streptococcal Pyoderma or for acute glomerulogephritis for which ASO titre is of much less value