Anti DNase B Antibody Test – Purpose, Procedure, and Normal Range

Overview

The Anti-DNase B Antibody Test is a blood test that measures antibodies produced by your immune system against an enzyme called Deoxyribonuclease B (DNase B). This enzyme is released by Group A beta-hemolytic Streptococcus bacteria — the same bacteria responsible for infections like strep throat and impetigo (skin infection).

Doctors use this test to determine if a person has had a recent or past streptococcal infection, especially when the infection itself is gone but has caused complications such as:

• Rheumatic fever (affects the heart, joints, and brain)
• Post-streptococcal glomerulonephritis (PSGN) (a kidney disorder)

This test is often performed when the ASO (Antistreptolysin O) test is negative, but a strep-related illness is still suspected.

What Is the Anti-DNase B Test?

The Anti-DNase B Test detects antibodies that target the bacterial enzyme DNase B.
When the immune system detects an infection caused by Group A Streptococcus, it produces these antibodies as a defense mechanism.

Even after the infection has cleared, Anti-DNase B antibodies can stay in the bloodstream for several weeks to months, making them useful for identifying past infections and delayed complications like rheumatic fever or kidney inflammation.

This makes the test particularly valuable in cases where:

• The infection symptoms have already disappeared.
• Throat cultures or swab tests are no longer positive.
• Doctors suspect post-streptococcal complications.

Where Are Anti-DNase B Antibodies Produced?

Anti-DNase B antibodies are produced by B lymphocytes (a type of white blood cell).
When the immune system detects the DNase B enzyme released by Group A Streptococcus bacteria, it begins producing antibodies against it.

Production sites include:

• Lymphoid tissues (like lymph nodes and tonsils)
• Bone marrow

These antibodies circulate in the blood to neutralize the bacterial enzyme and protect the body — but their presence later on indicates that a strep infection recently occurred.

Main Functions and Importance

These antibodies do not have any normal biological function in a healthy body.
However, they are very important from a diagnostic perspective.

Clinical Importance:

• Detects a recent streptococcal infection, even if bacteria are no longer present.
• Helps confirm post-streptococcal complications such as:
  • Rheumatic fever: affects the heart, joints, skin, and brain.
  • Post-streptococcal glomerulonephritis (PSGN): inflammation of the kidneys.
• Supports diagnosis when the ASO test (another strep antibody test) is negative.
• Helps distinguish between a current infection and a past one based on antibody levels.

Together with the ASO test, the Anti-DNase B test increases diagnostic accuracy for strep-related illnesses.

Causes of Low or Negative Levels

Low or negative Anti-DNase B levels generally mean:

• No recent Group A Streptococcal infection.
• The infection occurred too recently, and antibodies haven’t developed yet (test done too early).
• A mild infection that did not trigger a strong immune response.
• Antibody levels have declined naturally after a few months post-infection.

Symptoms of Low Levels

Low or negative Anti-DNase B levels do not cause symptoms.
They simply show that your immune system is not currently producing these antibodies — either because there was no infection or because the infection occurred long ago.

Causes of High Anti-DNase B Levels

Elevated Anti-DNase B levels indicate recent or ongoing immune response to a Group A Streptococcal infection.

Common causes include:

1. Recent strep infections:
   • Throat infections (Strep throat)
   • Skin infections (Impetigo)
2. Post-streptococcal complications:
   • Rheumatic fever
   • Post-streptococcal glomerulonephritis (PSGN)
3. Streptococcal carriers:
   Some people carry the bacteria in their throat or skin without showing symptoms but still have antibodies in their blood.

Symptoms of High Levels

High Anti-DNase B levels themselves don’t cause symptoms but usually appear after a streptococcal infection.
Patients may experience:

• Recent sore throat or skin infection (a few weeks earlier)
• Fever, fatigue, joint pain, and weakness
• Swelling or pain in joints (sign of rheumatic fever)
• Rash or nodules under the skin
• Heart symptoms: chest pain, shortness of breath (due to heart inflammation in rheumatic fever)
• Kidney issues: dark urine, puffiness around the eyes, or swelling in hands and feet — symptoms of PSGN

Reference Ranges

(Values may vary slightly among laboratories)

High levels should be interpreted alongside symptoms and other test results (like ASO, throat culture, or urinalysis).

Sample Type and Test Method

• Sample Required: Serum (blood sample)
• Tube Type: Serum Separator Tube (SST / Red Top)
• Test Method Used: Nephelometry or ELISA (Enzyme-linked immunosorbent assay)

This test measures the antibody concentration in units per milliliter (U/mL).

Test Preparation

• No fasting required.
• Inform your doctor about recent infections or antibiotics.
• If the test is done too early (within the first week of infection), it may not show high antibody levels.
  → In that case, the doctor may advise a repeat test after 2–3 weeks to see if levels rise.

When to Consult a Doctor

You should see a doctor if you experience:

• Joint pain, swelling, or stiffness after a throat/skin infection
• Fever, fatigue, or unexplained weakness
• Swelling around eyes, hands, or feet
• Dark-colored urine (possible kidney inflammation)
• Symptoms of rheumatic fever (chest pain, rash, nodules, joint pain)

The doctor may order:

• ASO test
• Urine test (for kidney function)
• ECG or echocardiogram (for heart function)
  to confirm and assess the extent of post-streptococcal complications.

Important Word Explanations

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