Definition

Anti-DNase B is a blood test to look for antibodies to a substance (protein) produced by group A streptococcus. This is the bacteria that cause strep throat.

When used together with the ASO titer test, more than 90% of past streptococcal infections can be identified.

Alternative Names

Strep throat - anti-DNase B test; Antideoxyribonuclease B titer; ADN-B test

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

No special preparation is necessary.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

This test is most often done to tell if you have previously had a strep infection and if you might have rheumatic fever or kidney problems (glomerulonephritis) due to that infection.

Normal Results

A negative test is normal. Some people have low concentrations of antibodies, but they have not had a recent strep infection. Therefore, normal values in different age groups are:

• Adults: less than 85 units/milliliter (mL)
• School-age children: less than 170 units/mL
• Preschool children: less than 60 units/mL

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different specimens. Talk to your health care provider about the meaning of your specific test results.

What Abnormal Results Mean

Increased levels of DNase B levels indicate exposure to group A streptococcus.

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks:

• Excessive bleeding
• Fainting or feeling lightheaded
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Bryant AE, Stevens DL. Streptococcus pyogenes. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 197.