A girl comes with symptoms of involuntary movements. Sydenham's chorea and acute rheumatic fever is suspected. Other major criteria of rheumatic fever (ahritis, skin rashes, subcutaneous nodules and carditis) were absent. No evidence of sore throat. Best investigation to prove rheumatic etiology is:

Ans: B. Antistreptolysin OAntistreptolysin O(ASLO):Marker for recent streptococcal infection.Best investigation to prove rheumatic etiology. Suppoing evidence:Preceding streptococcal infection within last 45 days.Elevated or rising anti-streptolysin O/other streptococcal antibodies.A positive throat culture.Rapid antigens test for group A streptococcus.Recent scarlet fever."Revised Jones" criteria do not include recent scarlet fever as suppoing evidence of recent streptococcal.