<prompt> All of the following are TRUE about ASO titre, EXCEPT:ASO can be increased in school childrenMay be negative in post streptococcal glomerulonephritisASO titre included in major criteria in jones criteriaMay not be elevated in 20 cases of carditis  <response>: The antistreptolysin O ASO titer is the most commonly used streptococcal antibody test to establish a recent streptococcal infection. It is not a major criteria but, suppoing evidence of antecedent group A streptococcal infection. An ASO titer of 240 Todd units or higher in adults or 320 Todd units or higher in children is considered modestly elevated. ASO titers above 500 Todd units are uncommon in healthy individuals and therefore would serve as evidence of a recent streptococcal infection. Ref: Jaggi P., Shulman S.T. 2013. Chapter 52. Rheumatic Fever. In J.B. Imboden, D.B. Hellmann, J.H. Stone Eds, CURRENT Diagnosis Treatment: Rheumatology, 3e. 