Antipolysaccharide group-specific antibodies of Streptococcus pyogenes in children.

Evaluation of a new microtest for the detection of Streptococcus pyogenes group A antipolysaccharide antibodies in 996 control children and 562 streptococcal infections from 0 to 12 years. The case-list was divided in 4 groups, years 0-2. 2-4. 4-8. 8-12 for the evaluation of the age-related normality range. Under 2 years normal values between 60 and 120 U, from 2 to 12 years normal values under 240 U. In streptococcal infections identical patterns for the pathological values in the 4 age-ranges considered, with positivity percentage from 85% to 95%, thus confirming the same antibody response also in breast-fed children, unlike what occurs for ASO under 2 years, when the response is present only in 25% of the cases and in the 2-4 years age-range in 33.3%. Evident diagnostic superiority of MSK as compared with ASO in adenitis, pyodermic infections, bronchopneumopathies, acute tonsillitis at the onset of symptomatology. In rheumatic disease the percentage of positivity for MSK and ASO is similar, in post-streptococcal glomerulonephritis and in Schoenlein-Henoch syndrome the percentage of positivity for MSK is higher than for ASO. It is suggested the utility of insertion of MSK test in the routine assay for streptococcal infections diagnosis above all in children under 4 years and in infections with low or slow antigenic charge for 0-streptolysin.