ASO titire Is diagnostic in ?

Ref: R Alagappan - Manual of Practical Medicine 4th Edition.pg no:146-147 Essential Criteria Evidence for recent streptococcal infection as evidenced by: 1. Increase in ASO titre a. > 333 Todd units (in children) b. > 250 Todd units (in adults). 2. Positive throat culture for streptococcal infection. 3. Recent history of scarlet fever. Two major (or) one major and two minor criteria, in the presence of essential criteria, is required to diagnose Acute Rheumatic Fever. A Positive Rheumatic Fever history is usually elicited in only 50% of patient with Rheumatic Hea Disease.