The prevalence of streptococcus group A infection among Ha Noi pupils and error leading to misdiagnosis

1266 school children aged 6-15 years at 10 schools in Hanoi were enrolled into an investigation on Streptococci group A infection. At the pharynx a prevalence of 15.3% was shown. Predominant titre of antibody against streptolysine O was from 25 to 100 Todd units and only 9% had got the titre over 240 units. Alpha hemolytic Streptococcus viridans could be wrongly identified with beta hemolytic one leading to an error to 60% in bacitracine tests. Pseudo-positive identification may happened in ASLO test if the sample of serum had been infected