Anti-DNase B

• Illustrations
• Definition
• How the test is performed
• How to prepare for the test
• How the test will feel

• Why the test is performed
• Normal Values
• What abnormal results mean
• What the risks are
• Special considerations

Definition    Return to top

This is a blood test used to detect antibodies against antideoxyribonuclease B (anti-DNase B), an antigen produced by group A streptococci.

How the test is performed    Return to top

Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test    Return to top

No special preparation is necessary.

For infants and children:

The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics:

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How the test will feel    Return to top

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed    Return to top

This test is most often used to confirm a previous streptococcal infection.

Normal Values    Return to top

A "negative" test is normal.

• adults: less than 85 Todd units/ml
• school-age children: less than 170 Todd units/ml
• preschool children: less than 60 Todd units/ml

What abnormal results mean    Return to top

Elevated DNase B levels may indicate:

• rheumatic fever
• post-streptococcal glomerulonephritis after strep throat or streptococcal skin infections

What the risks are    Return to top

• excessive bleeding
• fainting or feeling light-headed
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations    Return to top

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

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.