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DNase B is an enzyme produced by almost all strains of beta hemolytic Group A and a few strains of Group C and G streptococci. Patients infected with these strains of streptococci form antibodies against DNase B. Serologic tests for anti-DNase B are helpful in confirming the diagnosis of streptococcal infections. The anti-DNase B test is an enzyme neutralization test, measuring the ability of specific antibodies to inhibit the depolymerization of DNA. Various dilutions of serum are tested. The reciprocal of the highest dilution of serum showing inhibition is the anti-DNase B titer. Elevated titers are found in approximately 80% of acute rheumatic fever cases. An elevated anti-DNase B titer is helpful in diagnosing acute rheumatic fever in the 20% of patients who do not have elevated ASO titers. Anti-DNase B titers rise more slowly than ASO titers, peaking four to eight weeks after infection. They also decline much more slowly, remaining elevated for several months. Following streptococcal pyoderma, which may result in poststreptococcal glomerulonephritis, less than 50% of patients develop elevated ASO titers. In contrast, most patients develop elevated anti-DNase B titers, which remain elevated for many months. Therefore, anti-DNase B is the preferred serological test. Because of its prolonged elevation, anti-DNase B may also be helpful in diagnosing the delayed sequelae of Sydenham's chorea. The reference range is age specific:
Specimen requirement is one plain red top or SST tube of blood. SST tube needs to be centrifuged within 30 minutes of drawing and refrigerated. |
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