Quantitative Analysis of Antideoxyribonuclease B Concentrations in the Carriers of Beta-hemolytic Streptococci

ABSTRACT

Although throat culture is a gold standard to diagnose group A streptococcal (GAS) pharyngitis or its sequelae, antistreptolysin O (ASO) is useful to confirm the diagnosis. In case there is no elevation of ASO, it is necessary to add one or more serologic tests, such as antideoxyribonuclease (ADNase) B test. ADNase B levels were analyzed in the carriers of beta-hemolytic streptococci (BHS) in this study. ADNase B concentrations were determined quantitatively by nephelometry (Behring Nephelometer 100 Analyzer, Germany) on 157 sera of healthy elementary school children in Chungnam who were positive of BHS in the throat culture. ASO levels were measured previously by autoanalyzer (Hitachi 747, Japan). Mean ADNase B and ASO levels were compared according to serological group of BHS and number of colonies. The carriers of GAS had significantly higher ADNase B levels (mean 453 IU/ml) than those of non-A beta-hemolytic streptococci (NGAS, 278 IU/ml), while the difference of ASO levels between GAS (482 IU/ml) and NGAS (350 IU/ml) carriers was not so high. The carriers who had more than 10 CFU of BHS had significantly higher ADNase B or ASO levels than those who had less than 10 CFU. The correlation between ADNase B (Y) and ASO (X) was Y=0.4X+229 (r2=0.13). ADNase B test could discriminate GAS from NGAS more effectively than ASO test. The carriers who have more than 10 CFU might undergo asymptomatic infection, as their ADNase B or ASO levels were significantly high. Because distribution of ADNase B showed little correlation to that of ASO, ADNase B test could be used as a supplementary test to diagnose GAS infection.