This test helps determine whether you have had a recent strep infection with the bacteria group A Streptococcus.
This test can help to diagnose complications resulting from a recent strep infection, such as rheumatic fever or glomerulonephritis, a form of kidney disease.
What is a strep infection?
Viruses are the most common cause of a sore throat. However, strep throat is an infection in the throat and tonsils caused by bacteria called group A Streptococcus (group A strep).
Group A strep live in the nose and throat and can easily spread to other people. People who are infected spread the bacteria by talking, coughing, or sneezing, which creates small respiratory droplets that contain the bacteria. They can also spread the bacteria from infected sores on their skin.
It usually takes two to five days for someone exposed to group A strep to become ill with strep throat.
It is important to know that some infected people do not have symptoms or seem sick. People sick with strep throat are much more contagious than those who do not have symptoms.
People can get sick if they:
- Breathe in respiratory droplets that contain the bacteria
- Touch something with those droplets on it and then touch their mouth or nose
- Drink from the same glass or eat from the same plate as a person infected with group A strep
- Touch sores on the skin caused by group A strep or come into contact with fluid from the sores
Rarely, people can spread group A strep through food that is not handled properly.
What are possible symptoms of a strep infection?
When you have symptoms such as fever, chest pain, fatigue and shortness of breath that suggest rheumatic fever, or symptoms such as accumulation of fluid (edema) and dark urine that are associated with glomerulonephritis, especially when you recently may have had a group A streptococcal infection that was not diagnosed and treated appropriately.
What is Anti-DNase B?
Anti-DNase B (antideoxyribonuclease-B antibody) is one of the most common of several antibodies that are produced by the body’s immune system in response to an infection with group A Streptococcus (strep infection). The anti-DNase B test measures the amount of this antibody in the blood. It is typically done with or following an antistreptolysin O (ASO) test, another test to detect antibody to a streptococcal antigen.
Group A Streptococcus, primary and secondary conditions:
Group A Streptococcus (Streptococcus pyogenes), is the bacterium that causes strep throat and a variety of other infections, including skin infections (pyoderma, impetigo, cellulitis). In most cases, strep infections are diagnosed and successfully treated with antibiotics.
Sometimes a strep infection does not cause identifiable symptoms, goes untreated, or is treated ineffectively, and complications (sequelae), namely rheumatic fever and glomerulonephritis, can develop, especially in young children. These secondary conditions are uncommon in the U.S. because of routine strep testing and antibiotic treatment, but they do occur.
Rheumatic fever is a delayed immune response in which the body produces antibodies directed against itself (autoimmune). This can cause serious damage to heart valves and lead to symptoms such as swelling and pain in several joints, heart inflammation (carditis), skin nodules, rapid, jerky movements (Sydenham chorea), and skin rash.
Post-streptococcal glomerulonephritis, a condition affecting the kidneys, can develop a week or two after a strep infection. Your body produces antibodies to fight the strep infection, but these antibodies can eventually be deposited in the glomeruli, which are small, looping blood vessels within the kidneys that continually filter the blood. This can cause inflammation and kidney damage, affecting kidney function.
Negative anti-DNase B and ASO tests or very low titers means that it is unlikely you had a recent strep infection. This is especially true if a sample taken 10 to 14 days later is also negative. Your signs and symptoms are likely due to a cause other than a recent strep infection
People can get strep throat more than once. Having strep throat does not protect someone from getting it again in the future. While there is no vaccine to prevent strep throat, there are things people can do to protect themselves and others.
Good hygiene helps prevent group A strep infections
The best way to keep from getting or spreading group A strep is to wash your hands often. This is especially important after coughing and sneazingn and before preparing foods or eating.
To prevent group A strep infections, you should:
- Cover your mouth and nose with a tissue when you cough or sneeze.
- Put your used tissue in the waste basket.
- Cough or sneeze into your upper sleeve or elbow, not your hands, if you don’t have a tissue.
- Wash your hands often with soap and water for at least 20 seconds.
- Use an alcohol-based hand rub if soap and water are not available.
You should also wash glasses, utensils, and plates after someone who is sick uses them. These items are safe for others to use once washed.
Increased levels of DNase B levels indicate exposure to group A Streptococcus.
Anti-DNase B and ASO test results may be interpreted together. Anti-DNase B and ASO antibodies are produced about a week to a month after a 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.
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.
Elevated or rising antibody titers of anti-DNase or ASO means that it is likely you had a recent strep infection.
If your have signs and symptoms of rheumatic fever or glomerulonephritis, an elevated anti-DNase B and/or ASO titer can help confirm the diagnosis.
Doctors treat strep throat with antibiotics. Either penicillin or amoxicillin are recommended as a first choice for people who are not allergic to penicillin. Doctors can use other antibiotics to treat strep throat in people who are allergic to penicillin.
Benefits of antibiotics include:
- Decreasing how long someone is sick
- Decreasing symptoms (feeling better)
- Preventing the bacteria from spreading to others
- Preventing serious complications like rheumatic fever
Someone who tests positive for strep throat but has no symptoms (called a “carrier”) usually does not need antibiotics. They are less likely to spread the bacteria to others and very unlikely to get complications. If a carrier gets a sore throat illness caused by a virus, the rapid strep test can be positive. In these cases, it can be hard to know what is causing the sore throat. If someone keeps getting a sore throat after taking the right antibiotics, they may be a strep carrier and have a viral throat infection. Talk to a doctor if you think you or your child may be a strep carrier.
Complications can occur after a strep throat infection. This can happen if the bacteria spread to other parts of the body. Complications can include:
- Abscesses (pockets of pus) around the tonsils or in the neck
- Swollen lymph nodes in the neck
- Sinus infections
- Ear infections
- Rheumatic fever (a disease that can affect the heart, joints, brain, and skin)
- Post-streptococcal glomerulonephritis (a kidney disease)
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