Demonstration of acute or recent streptococcal infection using anti-DNase B titer.
<5 years: <=250 U/ml
5-17 years <=375 U/ml
>=18 years: <=300 U/ml
Elevated values are
consistent with an antecedent infection by group A streptococci. Although the
antistreptolysin O (ASO) test is quite reliable, performing the anti-DNase is
justified for 2 primary reasons.
First, the ASO
response is not universal. Elevated
ASO titers are found
in the sera of about
85% of individuals with rheumatic fever;
ASO titers remain normal in about 15% of individuals
with the disease. The same holds true for other streptococcal antibody
tests: a significant portion of individuals with normal antibody
titers for 1 test
will have elevated
antibody titers for another test.
Thus, the percentage of false negatives can be reduced
by performing 2 or more
antibody tests. Second,
skin infections, in contrast
to throat infections, are associated with a poor ASO response. Patients with
acute glomerulonephritis following skin infection (post-impetigo) have an
attenuated immune response to streptolysin 0. For such patients, performance of
an alternative streptococcal antibody test,
such as this
assay, is recommended.