Anti-streptococcal antibodies in the diagnosis of acute and poststreptococcal disease: streptokinase versus streptolysin O and deoxyribonuclease B

Abstract

To establish population normal values and compare the diagnostic value of antibodies against streptokinase (ASK), streptolysin O (ASO) and deoxyribonuclease B (ADNaseB) singularly and in combinations in acute and post-streptococcal disease. A retrospective analysis of serological results was performed to define population norms. Subjects with acute culture-confirmed infection and post-streptococcal disease were assessed using population norms, as were matched controls. The sensitivity and specificity of each antibody assay and of combinations of the different assays were calculated. Age specific population normal values were derived from 2,321 specimens. None of the three antibodies alone or in combination was a reliable marker of acute streptococcal infection. The sensitivity and specificity of a single antibody titre in post-streptococcal disease ranged from 70.5 to 72.7% and 86.4 to 93.2%, respectively. The combination of ASO and ADNaseB was the most sensitive and specific combination for identifying post-streptococcal disease (sensitivity 95.5%, specificity 88.6%). In the diagnosis of acute and post-streptococcal disease, the addition of ASK does not increase the sensitivity or specificity of serological testing. A combination of ASO and ADNaseB is required in post-streptococcal disease to achieve maximum sensitivity and specificity.