HLA-B27 antigen test
HLA-B27 is a blood test to look for a protein that is found on the surface of white blood cells. The protein is called human leukocyte antigen B27 (HLA-B27).
Human leukocyte antigens (HLAs) are proteins that help the body's immune system tell the difference between its own cells and foreign, harmful substances.
How the Test is Performed
A blood sample is needed. Most of the time, blood is drawn from a vein located on the inside of the elbow or the back of the hand.
How to Prepare for the Test
In most cases, no special steps are needed to prepare for the test.
How the Test will Feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
Your health care provider may order this test to help determine the cause of joint pain, stiffness, or swelling. The test may be done along with other tests, including:
-C-reactive protein
-Erythrocyte sedimentation rate (ESR)
-Rheumatoid factor
-X-rays
HLA testing is also used to match donated tissue with a person's tissue who is getting an organ transplant. For example, it may be done when a person needs a kidney transplant or bone marrow transplant.
Normal Results
A normal (negative) result means HLA-B27 is absent.
What Abnormal Results Mean
A positive test means HLA-B27 is present. It suggests a greater-than-average risk for developing or having certain autoimmune disorders. An autoimmune disorder is a condition that occurs when the immune system mistakenly attacks and destroys healthy body tissue.
A positive result can help your provider make a diagnosis of a form of arthritis called spondyloarthritis. This kind of arthritis includes the following disorders:
-Ankylosing spondylitis
-Arthritis related to Crohn disease or ulcerative colitis
-Psoriatic arthritis (arthritis associated with psoriasis)
-Reactive arthritis
-Sacroiliitis (inflammation of the sacroiliac joint)
-Uveitis
If you have symptoms or signs of spondyloarthritis, a positive HLA-B27 test may help confirm the diagnosis. However, HLA-B27 is found in some normal people and does not always mean you have a disease.
Risks
Risks from having blood drawn are slight, but may include:
-Excessive bleeding
-Fainting or feeling lightheaded
-Hematoma (blood accumulating under the skin)
-Infection (a slight risk any time the skin is broken)
HIV Screening Test
What is an HIV test?
An HIV test shows whether you are infected with HIV (human immunodeficiency virus). HIV is a virus that attacks and destroys cells in the immune system. These cells protect your body against disease-causing germs, such as bacteria and viruses. If you lose too many immune cells, your body will have trouble fighting off infections and other diseases.
There are three main types of HIV tests:
Antibody Test. This test looks for HIV antibodies in your blood or saliva. Your immune system makes antibodies when you are exposed to bacteria or viruses, like HIV. An HIV antibody test can determine if you have HIV from 3–12 weeks after infection. That's because it can take a few weeks or longer for your immune system to make antibodies to HIV. You may be able to do an HIV antibody test in the privacy of your home. Ask your health care provider about at-home HIV test kits.
HIV Antibody/Antigen Test. This test looks for HIV antibodies and antigens in the blood. An antigen is a part of a virus that triggers an immune response. If you've been exposed to HIV, antigens will show up in your blood before HIV antibodies are made. This test can usually find HIV within 2–6 weeks of infection. The HIV antibody/antigen test is one of the most common types of HIV tests.
HIV Viral Load. This test measures the amount of the HIV virus in the blood. It can find HIV faster than antibody and antibody/antigen tests, but it is very expensive. It is mostly used for monitoring HIV infections.
Other names: HIV antibody/antigen tests, HIV-1 and HIV-2 antibody and antigen evaluation, HIV test, human immunodeficiency virus antibody test, type 1, HIV p24 antigen test
What is it used for?
An HIV test is used to find out if you have been infected with HIV. HIV is the virus that causes AIDS (acquired immunodeficiency syndrome). Most people with HIV don't have AIDS. People with AIDS have an extremely low number of immune cells and are at risk for life-threatening illnesses, including dangerous infections, a severe type of pneumonia, and certain cancers, including Kaposi sarcoma.
If HIV is found early, you can get medicines to protect your immune system. HIV medicines may prevent you from getting AIDS.
Why do I need an HIV test?
The Centers for Disease Control and Prevention (CDC) recommends that everyone between the ages of 13 and 64 get tested for HIV at least once as part of routine health care. You may also need an HIV test if you are at higher risk for infection. HIV is mainly spread through sexual contact and blood, so you may be at a higher risk for HIV if you:
Are a man that has had sex with another man
Have had sex with an HIV-infected partner
Have had multiple sex partners
Have injected drugs, such as heroin, or shared drug needles with someone else
HIV can spread from mother to child during birth and through breast milk, so if you are pregnant your doctor may order an HIV test. There are medicines you can take during pregnancy and delivery to greatly reduce your risk of spreading the disease to your baby.
What happens during an HIV test?
You will either get a blood test in a lab, or do your own test at home.
For a blood test in a lab:
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
For at home test, you will need to get a sample of saliva from your mouth or a drop of blood from your fingertip.
The test kit will provide instructions on how to get your sample, package it, and send it to a lab.
For a saliva test, you will use special spatula-like tool to take a swab from your mouth.
For a fingertip antibody blood test, you will use a special tool to prick your finger and collect a sample of blood.
For more information on at-home testing, talk to your health care provider.
Will I need to do anything to prepare for the test?
You don't need any special preparations for an HIV test. But you should talk with a counselor before and/or after your test so you can better understand what the results mean and your treatment options if you are diagnosed with HIV.
Are there any risks to the test?
There is very little risk to having any HIV screening test. If you get a blood test from a lab, you may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What do the results mean?
If your result is negative, it can mean you don't have HIV. A negative result may also mean you have HIV but it's too soon to tell. It can take a few weeks for HIV antibodies and antigens to show up in your body. If your result is negative, your health care provider may order additional HIV tests at a later date.
If your result is positive, you will get a follow-up test to confirm the diagnosis. If both tests are positive, it means you have HIV. It does not mean you have AIDS. While there is no cure for HIV, there are better treatments available now than in the past. Today, people with HIV are living longer, with a better quality of life than ever before. If you are living with HIV, it's important to see your health care provider regularly.
Hemoglobin Test
What is a Hemoglobin Test?
A hemoglobin test measures the levels of hemoglobin in your blood. Hemoglobin is a protein in your red blood cells that carries oxygen from your lungs to the rest of your body. If your hemoglobin levels are abnormal, it may be a sign that you have a blood disorder.
Other names: Hb, Hgb
What is it used for?
A hemoglobin test is often used to check for anemia, a condition in which your body has fewer red blood cells than normal. If you have anemia, your cells don't get all the oxygen they need. Hemoglobin tests are also frequently performed with other tests, such as:
Hematocrit, which measures the percentage of red blood cells in your blood
Complete blood count, which measures the number and type of cells in your blood
Why do I need a hemoglobin test?
Your health care provider may have ordered the test as part of a routine exam, or if you have:
Symptoms of anemia, which include weakness, dizziness, pale skin, and cold hands and feet
A family history of thalassemia, sickle cell anemia, or other inherited blood disorder
A diet low in iron and minerals
A long-term infection
Excessive blood loss from an injury or surgical procedure
What happens during a hemoglobin test?
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
You don't need any special preparations for a hemoglobin test. If your health care provider has also ordered other blood tests, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms usually go away quickly.
What do the results mean?
There are many reasons your hemoglobin levels may be outside the normal range.
Low hemoglobin levels may be a sign of:
Different types of anemia
Thalassemia
Iron deficiency
Liver disease
Cancer and other diseases
High hemoglobin levels may be a sign of:
Lung disease
Heart disease
Polycythemia vera, a disorder in which your body makes too many red blood cells. It can cause headaches, fatigue, and shortness of breath.
If any of your levels are abnormal, it does not necessarily indicate a medical problem needing treatment. Diet, activity level, medications, a women's menstrual cycle, and other considerations can affect the results. In addition, you may have higher than normal hemoglobin if you live in a high altitude area. Talk to your health care provider to learn what your results mean.
Is there anything else I need to know about a hemoglobin test?
Some forms of anemia are mild, while other types of anemia can be serious and even life-threatening if not treated. If you are diagnosed with anemia, be sure to talk to your health care provider to find out the best treatment plan for you.
What is an ELISA test?
An ELISA test uses components of the immune system (such as IgG or IgM antibodies) and chemicals for the detection of immune responses in the body (for example, to infectious microbes). The ELISA test involves an enzyme (a protein that catalyzes a biochemical reaction). It also involves an antibody or antigen (immunologic molecules). Examples of the uses of an ELISA test includes to diagnose infections such as HIV (human immunodeficiency virus) and some allergic diseases like food allergies. ELISA tests are also known as an immunosorbent assay.
What is the use of an ELISA test?
ELISA tests are primarily used for the detection of proteins (as opposed to small molecules and ions such as glucose and potassium). The substances detected by ELISA tests can include hormones, viral antigens (dengue fever, for example), bacterial antigens (TB, for example), and antibodies that the body has made in response to infection (antibodies to hepatitis B, for example) or vaccination.
What is an ELISA kit?
An ELISA kit is a commercially available ELISA test that usually contains pre-coated polystyrene plates, detection antibodies, and usually all of the chemicals needed to perform an ELISA test. However, special kits can be purchased with substances designated by the customer.
How do health care workers perform an ELISA test?
Health care personnel who perform the test are trained laboratory technicians who use special kits that measure the antigens' interactions with the antibodies in the kit. They will inform your doctor of the test results.
How does ELISA testing work?
There are variations of the ELISA test (see below), but the most utilized type consists of an antibody attached to a solid surface (polystyrene plate). This antibody has affinity for (will latch on to) the substance of interest, such as a hormone, bacteria, or another antibody. For example, human chorionic gonadotropin hormone (HCG), the commonly measured protein which indicates pregnancy, can be detected by ELISA. A mixture of purified HCG linked to an enzyme and the test sample (blood or urine) are added to the test system. If no HCG is present in the test sample, then only the linked enzyme will bind to the solid surface. The more substance of interest that is present in the test sample, the less linked enzyme will bind to the solid surface. The more of the substance of interest is present it will cause a reaction and show up on the test plate in some way, such as a change in color of the solution (or like a pregnancy test "two pink lines" or a "+" mark).
Types of ELISA Tests
HIV Test
Antibody testing is usually done on a blood sample, often using an enzyme-linked assay called an ELISA or EIA. In this test, a person's serum is allowed to react with virus proteins that have been produced in the laboratory. If the person has been infected with HIV, the antibodies in the serum will bind to the HIV proteins, and the extent of this binding can be measured. Negative EIA results are usually available in a day or so.
What are the types of ELISA tests? What is a direct ELISA?
There are four types or kinds of ELISA tests:
Direct ELISA: attachment of an antigen to a polystyrene plate followed by an enzyme-labeled antibody that can react with the antigen and a substrate that can be measured
Indirect ELISA: attachment of an antigen to a polystyrene plate followed by an unlabeled or primary antibody followed by an enzyme-labeled antibody that can react with both the primary antibody and substrate
Sandwich ELISA: A capture antibody is attached to the polystyrene plate, then antigen is added that specifically attaches or captures the antigen. A second antibody, also specific for the antigen but not the same as the capture antibody is added and "sandwiches" the antigen. This second antibody is then followed by an enzyme-labeled antibody specific for the second antibody that can react with a substrate that can be measured
Competitive ELISA: This test is like the sandwich ELISA but involves the addition of competing antibodies or proteins when the second antibody is added. This results in a decrease in the substrate signal that is generated. This test is considered to give good, highly specific results.
What are the advantages of ELISA testing?
ELISA tests are generally good and accurate tests. They are considered highly sensitive and specific (accurate) and compare favorably with other methods used for the detection of substances in the body. The ELISA testing method is more straightforward and easier to perform than older laboratory techniques, which often required radioactive materials.
How do people prepare for an ELISA test? Is an ELISA test painful? What risks are involved with an ELISA procedure?
In general, people do not need to prepare for an ELISA test. The test is done in a lab. If your blood is required, the only hurt is in blood collection. The risks associated with an ELISA test are rare and associated with blood withdrawal (infection, vessel damage, for example).
How long does it take to get ELISA test results?
Depending on what the test is being used for, you may get results as quickly as about 24 hours if the test is done locally. However, there are some tests that may take days to weeks.
What do the results of an ELISA test mean?
There are many hundreds of variations of ELISA tests. The results and their meaning depend on what is being tested. For example, an ELISA test for viral RNA can detect it (a positive test), not detect it (a negative test), or be indeterminate (borderline test). Rarely, it may result in a false negative or false positive result. If you have an ELISA test done, the best approach is to ask your physician what the results of the test mean to your individual situation.
Dengue Fever Test
What is a dengue fever test?
Dengue fever is a viral infection spread by mosquitos. The virus can't be spread from person to person. Mosquitos that carry the dengue virus are most common in areas of the world with tropical and subtropical climates.
Most people who get dengue fever have no symptoms, or mild, flu-like symptoms such as fever, chills, and headache. These symptoms usually last for a week or so. But sometimes dengue fever can develop into a much more serious disease called dengue hemorrhagic fever (DHF).
DHF causes life-threatening symptoms, including blood vessel damage and shock. Shock is a condition that can lead to a severe drop in blood pressure and organ failure.
DHF mostly affects children under 10. It can also develop if you have dengue fever and get infected a second time before you have fully recovered from your first infection.
A dengue fever test looks for signs of the dengue virus in the blood.
While there is no medicine that can cure dengue fever or DHF, other treatments can help relieve symptoms. This can make you more comfortable if you have dengue fever. It can be lifesaving if you have DHF.
Other names: dengue virus antibody, dengue virus by PCR
What is it used for?
A dengue fever test is used to find out if you have been infected with the dengue virus. It is mostly used for people who have symptoms of illness and have recently traveled to an area where dengue infections are common.
Why do I need a dengue fever test?
You may need this test if you live or have recently traveled to an area where dengue is common, and you have symptoms of dengue fever. Symptoms usually show up four to seven days after being bitten by an infected mosquito, and may include:
Sudden high fever (104°F or higher)
Swollen glands
Rash on the face
Severe headache and/or pain behind the eyes
Joint and muscle pain
Nausea and vomiting
Fatigue
Dengue hemorrhagic fever (DHF) causes more severe symptoms and can be life-threatening. If you've had symptoms of dengue fever and/or have been in an area that has dengue, you may be at risk for DHF. Seek medical help immediately if you or your child has one or more of the following symptoms:
Severe abdominal pain
Vomiting that doesn't go away
Bleeding gums
Nose bleeds
Bleeding under the skin, which may look like bruises
Blood in urine and/or stools
Difficulty breathing
Cold, clammy skin
Restlessness
What happens during a dengue fever test?
Your health care provider will probably ask about your symptoms and for details on your recent travels. If an infection is suspected, you will get a blood test to check for the dengue virus.
During a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
You don't need any special preparations for a dengue fever test.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What do the results mean?
A positive result means you probably have been infected with the dengue virus. A negative result can mean you aren't infected or you were tested too soon for the virus to show up in testing. If you think you were exposed to the dengue virus and/or have symptoms of infection, talk to your health care provider about whether you need to be retested.
If your results were positive, talk to your health care provider about how to best treat your dengue fever infection. There are no medicines for dengue fever, but your provider will probably recommend that you get plenty of rest and drink lots of fluids to avoid dehydration. You may also be advised to take over-the-counter pain relievers with acetaminophen (Tylenol), to help ease body aches and reduce fever. Aspirin and ibuprofen (Advil, Motrin) are not recommended, as they may worsen bleeding.
If your results are positive and you have symptoms of dengue hemorrhagic fever, you may need to go to the hospital for treatment. Treatment may include getting fluids through an intravenous (IV) line, a blood transfusion if you've lost a lot of blood, and careful monitoring of blood pressure.
Is there anything else I need to know about a dengue fever test?
If you will be traveling to an area where dengue is common, you can take steps to reduce your risk of getting infected with the dengue virus. These include:
Apply an insect repellent containing DEET on your skin and clothing.
Wear long-sleeved shirts and pants.
Use screens on windows and doors.
Sleep under a mosquito net.