Anti-DNase B

The anti-DNase B test may be used to help determine whether a recent strep infection with group A Streptococcus:

• Is the cause of a person's glomerulonephritis, a form of kidney disease
• Caused rheumatic fever in a person with signs and symptoms

The test may be ordered with an ASO, another test used to detect prior strep infections.

In most cases, throat and skin strep infections are identified and treated with antibiotics and the infections resolve. In cases where the infections do not cause identifiable symptoms and/or go undiagnosed and untreated, however, complications (sequelae), namely rheumatic fever and glomerulonephritis, can develop in some people, especially young children.

If not diagnosed and treated appropriately, group A streptococcal throat infections (strep throat) can lead to either rheumatic fever or glomerulonephritis, while strep skin infections can lead to glomerulonephritis. The ASO test is ordered if a person presents with symptoms suggesting rheumatic fever or glomerulonephritis and has had a recent history of sore throat, characteristic skin infection, or a confirmed streptococcal infection.

The anti-DNase B test may be ordered by itself, or along with another streptococcal antibody test such as an antihyaluronidase, if the ASO test is negative. A small percentage (10-15%) of those with a post-streptococcal complication will not have an elevated ASO but may have an elevated anti-DNase B or antihyaluronidase titer. This is especially true with glomerulonephritis linked to a previous skin strep infection.

Since the incidence of post-streptococcal complications has dropped in the U.S., so has the use of the ASO test and anti-DNase B test.

The anti-DNase and ASO test are ordered when a person has symptoms that a health practitioner suspects may be due to an illness caused by a previous strep infection. They are ordered when the symptoms appear, usually in the weeks following a sore throat or skin infection when the bacteria are no longer present in the throat or on the skin.

An anti-DNase B and another streptococcal antibody test, such as an antihyaluronidase test, may be ordered when an ASO test is negative to seek confirmation of a previous strep infection.

Some symptoms of rheumatic fever may include:

• Fever
• Joint swelling and pain in more than one joint, especially in the ankles, knees, elbows and wrists, sometimes moving from one joint to another
• Small, painless nodules under the skin
• Rapid, jerky movements (Sydenham's chorea)
• Skin rash
• Sometimes the heart can become inflamed (carditis); this may not produce any symptoms but also may lead to shortness of breath, heart palpitations, or chest pain

Some symptoms of glomerulonephritis may include:

• Fatigue, decreased energy
• Decreased urine output
• Bloody urine
• Rash
• Joint pain
• Swelling (edema)
• High blood pressure

However, these symptoms can be seen in other conditions.

Anti-DNase B testing may be performed twice, with samples collected about two weeks apart, for acute and convalescent titers. This is done to determine if the antibody level is rising, falling, or remaining the same.

Anti-DNase B and ASO antibodies are produced about a week to a month after an initial strep infection. The amount of anti-DNase B antibody (titer) peaks about 4 to 6 weeks after the illness and may remain elevated for several months. They typically remain elevated longer than ASO antibody titers.

Negative anti-DNase B and ASO tests or these antibodies present at very low titers means that the person tested most likely has not had a recent strep infection. This is especially true if a sample taken 10 to 14 days later is also negative.

An elevated antibody titer of anti-DNase or ASO, or rising titer of these antibodies, means that it is likely that the person tested has had a recent strep infection. A small percentage (10-15%) of those who have a complication related to a recent strep infection will not have an elevated ASO titer. This is especially true with glomerulonephritis that develops after a skin strep infection. These people may, however, have an elevated anti-DNase B titer and/or an elevation in another streptococcal antibody such as an elevated antihyaluronidase titer.

The anti-DNase B and ASO tests do not predict if complications will occur following a streptococcal infection, nor do they predict the type or severity of the disease. If symptoms of rheumatic fever or glomerulonephritis are present, an elevated anti-DNase B and/or ASO titer may be used to help confirm the diagnosis.

If a person has an elevated and/or rising ASO titer, it is not necessary to test for anti-DNase B.However, if the ASO level is negative, then the anti-DNase B can be valuable for identifying previous strep infections in those people who either do not produce ASO or only produce minimal amounts of it.