What is the HLA-B27 test?
The HLA-B27 is a blood test that is used to determine the level of a particular protein called human leukocyte antigen B27(HLA-B27), which is also a genetic marker. The protein is an antigen that is found on the surface of white blood cells that are fighting infection in the body. Its basic purpose is to help the immune system in differentiating between the body’s own healthy cells and the harmful foreign substances. The detection of the protein is generally associated with autoimmune disorders related to spondylitis and arthritis.
In case you are detected positive for the antigen it does not necessarily mean that you are affected by any of these diseases. The context and the medical background of the patient have to be considered before a diagnosis.
What does a high level of this protein indicate?
In general, a significant section of the population ranging around 6 to 8%will test positive for this protein. In some cases, the HLA-B27 protein can cause the immune system to attack the otherwise healthy cells of the body resulting in auto-immune diseases. In terms of statistics, only 10 to 15% of the individuals carrying this protein will end up getting affected by some form of spondyloarthritis.
But almost 80-90% of people with ankylosing spondylitis are found to be positive for HLA-B27. It is also to be noted that around 10-20% of patients with proven ankylosing spondylitis will test negative for HLA B27. So the negative results of a test do not indicate that someone is free from the disease.
Each person has a distinct combination of HLA antigens depending on his or her genetic structure. The conditions associated with the antigen are usually chronic in nature and found more widely in men than in women. These conditions are also progressive in nature and the first symptoms are often observed in the early 30s. It may take several years before the degenerative changes are visible in the bones and joints through standard x-ray imaging or an MRI.
Why do I need to undergo an HLA-B27 test?
In general, the test can be associated with the symptoms of joint pain, swelling or joint stiffness. This can happen in the back, neck, and chest or the eyes. In many cases, the test is needed when the doctor suspects the disease but the characteristic traces are not visible in a normal x-ray image. The following symptoms are generally associated with an auto-immune disorder related to HLA-B27.
– Chronic joint pain or inflammation of joints
– Inflammation of urethra accompanied by skin lesions.
– Swelling or stiffness of the vertebrae in the spine, neck or in the chest area.
– Recurring inflammation and swelling of the middle of the eye.
The doctor generally orders for the test when any one of the following diseases related to the auto-immune disorder is suspected.
– Ankylosing spondylitis
– Reactive arthritis or Reiter’s syndrome
– Sacroiliitis associated with psoriasis
– Sacroiliitis associated with inflammatory bowel disease
– Acute Anterior uveitis
– Juvenile rheumatoid arthritis (JRA)
– Isolated peripheral enthesitis
The test is also done during any organ transplant to match the donated tissue with that of the patient. The test is also used in paternity cases as in case the child and father have same the unusual HLA genotype, paternity can be proven. The test can also be ordered as a part of a group of tests which may include a rheumatoid factor (RF) with either an erythrocyte sedimentation rate (ESR) or a C-reactive protein (CRP) test.
How is an HLA-B27 test performed?
The test is performed by drawing a blood sample from the body. The drawing process is also called venipuncture as blood is drawn from a vein, generally located on the inside of the elbow or the back of the hand. The process involves the following steps.
– The area where the needle will be inserted is disinfected by an antiseptic. An elastic band is tied in the upper arm to make the vein swell with blood, thus making collection easier.
– A needle is inserted into the vein and blood is drawn through it in an attached tube. You may feel moderate pain, or only a prick associated with some stinging sensation as the needle is inserted.
– The needle is withdrawn gently and pressure is applied to the area to prevent any excess bleeding. The spot is then covered with a sterile bandage.
– Since the size of the veins and arteries vary from one person to the other, the collection process may be difficult for some and multiple punctures may be needed.
The process is safe and can be concluded within a few minutes. In some cases, there might be a blood clot or excessive bleeding in the puncture site. Chances of infection are rare but might happen in exceptional cases.
What is the price of an HLA-B27 test in India?
The price for the test in India ranges between INR 1000 to INR2000 depending on the center and the facilities.
When will I get the test results?
The test results are generally available within a day but some centers may take up to a few days.
What is the normal range for an HLA-B27 test?
The test will indicate either the presence or the absence of HLA-B27, i.e. it will indicate a positive or negative result. The doctor will interpret the results in association with the symptoms, age, the gender of the patient and health history.
What do the results mean?
A positive result of the test in a person who does not have any symptoms or a family history of any HLA-B27 related auto-immune disease is not clinically significant. A positive result associated with the right symptoms, especially in a male patient below the age of 40 can be a sign of any of the diseases mentioned in the earlier segment. If the test is negative there is no association between the symptoms and HLA-B27 but the particular disease might still be there.
The test is not an actual diagnostic test but is generally be combined with multiple other tests to confirm the suspicions about a particular disorder. So further tests can be ordered to evaluate the symptoms in more detail.
Do I need to fast for the HLA-B27 test?
Fasting is not necessary for this test.
What else do I need to know before I appear for an HLA-B27 test?
There are a few points that can be kept in mind before appearing for the test.
– The presence of HLA-B27 in individuals is genetically determined and in case you have a family history of diseases related to it, you have a greater risk of developing such a disease.
– The antigen is most strongly associated with ankylosing spondylitis.
– There are some general physical symptoms of ankylosing spondylitis and it involves chronic pain associated with immobility that worsens at night and during early morning hours. In some cases, the stiffness is eased by physical activity and exercise.
– In a few patients, the joint inflammation may also be accompanied by mild to moderate anemia.
– The exact reason for the origin of auto-immune disorders is still not clear. In some cases, it is believed that the similarity between the HLA-B27 antigen and the antigens found on the cellular surface of the invading microorganisms trigger the immune system to act against both the healthy and disease-causing cells.
– The HLA-B27 can be divided into multiple subtypes and up to 105 different subtypes have been found. The exact relation between these types and the auto-immune diseases is not yet known.
Can pregnant women undergo an HLA-B27 test?
The test can be conducted on a pregnant woman without any restrictions.
Is the HLA-B27 test possible for new-born babies?
The test can be conducted on new-borns if it is suggested by a medical practitioner.
How many cases of ankylosing spondylitis reported in India each year?
It has been estimated that the prevalence of ankylosing spondylitis in India is roughly 0.2% of the general population. The prevalence of AS in the population is directly co-related to the prevalence of high HLA-B27 protein.
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