• Lab Tests

     
     
     
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    5/09/2014

    Blood Lab TestingPart of your physician’s toolkit for diagnosing and guiding treatment of cardiovascular disease will be laboratory tests. These tests, along with other in-office or in-hospital diagnostic tests such as electrocardiogram (ECG, EKG) and stress testing, and wearable or implantable longer-term monitors for at home testing, can help complete a diagnostic picture of your cardiovascular health.

    All of the lab tests described below are performed on a blood sample. It is likely that you have had blood drawn many times in the past, given the range of health information available through analyzing blood. Remember that while blood tests are a key diagnostic tool, your physician will consider your lab test results in conjunction with other test results and your individual risk factors, including your current health and individual and family medical histories.


    Lab tests:

     



    Platelet Function Test

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    Dr. Sandeep Nathan, of the University of Chicago Medical Center, explains when testing can be helpful to determine if blood-thinner medications are working for you.

    A platelet function test measures the rate at which your blood clots. Physicians who are treating cardiovascular patients will often order a platelet function test to see if antiplatelet medications that have been prescribed to prevent blood clots are working at their intended level. Platelet function tests can also be used to help identify the cause of excessive bleeding or to see if bleeding is a risk during surgery


    How Does It Work?

    Blood clotting is your body’s natural response to healing from an injury. Your blood begins to clot because of platelets - cell fragments in blood that clump together to prevent bleeding. Platelets cause clotting at injury sites, but they can sometimes also clump at the site of deposits of plaque - a fatty substance that builds up in your arteries and can contribute to a heart attack, stroke, or other problems. For this reason, cardiovascular patients are prescribed antiplatelet medications that reduce the ability of platelets to clump together. A platelet function test can tell a physician how fast a patient’s blood clots.

    In the lab, a technician follows a procedure to fill small sample chambers with blood where the clotting of platelets as it would occur in your body is simulated and measured as a function of time. The resulting information allows your physician to estimate the extent to which antiplatelet medications are working. 


    How Is It Performed?

    A platelet function test is like any other blood test. Having blood drawn typically only takes a few minutes. You will be asked to roll up your shirt sleeve (if necessary) and the medical professional who will be drawing the blood will swab the area where the needle will be inserted with an alcohol wipe. A rubber tube may be tied around the upper part of your arm, or you may be asked to make a fist, to make the veins stand out more and easier to access.

    A needle attached to a small test tube will be inserted into your vein and blood will begin to flow into the tube. When a sample that is appropriate for the test has been gathered, the needle will be removed, and you may be asked to press on a piece of gauze placed over the insertion site. This pressure will help stop any bleeding from the tiny puncture site. A bandage will then be placed over the site where the needle was inserted.

    Your blood sample will then be sent to lab technicians for analysis. You will receive information when you have the blood test as to when you can expect results.


    Is It Safe?

    Having blood drawn by a qualified medical professional is very safe. You will experience momentary pain when the needle is inserted, and you may experience bruising at the needle insertion site after the test is complete. If you have an allergy to latex or to any adhesives, let the person know who is drawing the blood so he or she can make any necessary adjustments.


    Questions to Ask Your Doctor About Platelet Function Tests

    The following questions can help you talk to your physician about having a platelet function test. Print out or write down these questions and take them with you to your appointment. Taking notes can help you remember your physician’s response when you get home.

    • Why are we testing how fast my blood clots?
    • What happens next if the test reveals that my blood is not clotting at the desired rate?

    Click here to download and print this list of questions. Take them with you to the doctor and share them with friends and loved ones when you are encouraging them to see their doctors.

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    Cholesterol/Lipids Test

    A blood cholesterol test gives your physician important information about your risk for cardiovascular disease and can also be used to see if medications prescribed to lower cholesterol levels are working. This blood test is used to measure total cholesterol levels, LDL (or “bad”) cholesterol, HDL (or “good”) cholesterol and triglycerides. When all types of blood fat are checked at the same time, it is called a lipoprotein profile.

    • LDL (low-density lipoprotein) cholesterol is often referred to as “bad” cholesterol because it causes plaque to build up inside the arteries. The maximum LDL for health in patients varies with medical history. An LDL cholesterol reading of over 130 mg/dl places someone at higher risk for cardiovascular events. With existing disease, the maximum may be 100 mg/dl, or even lower - for example 70 mg/dl if you have had a heart attack.
    • HDL (high-density lipoprotein) cholesterol is called “good” cholesterol because it helps keep cholesterol from building up inside the blood vessels. An HDL cholesterol reading below 40 indicates an increased risk for cardiovascular disease, and higher is always better.
    • Triglycerides are the third type of blood fat measured by the test. A triglyceride level of 200 or more indicates an increased risk of cardiovascular disease.


    How Does It Work?

    Your blood will be drawn and sent to a lab for analysis. The total cholesterol, LDL, HDL, or triglyceride levels in the blood may be measured individually or together as part of a lipoprotein profile. The test results will be communicated back to your physician.


    How Is It Performed?

    Before the test, be sure to follow any instructions given to you by your physician related to eating and drinking.

    A cholesterol/lipids test is like any other blood test. Having blood drawn typically only takes a few minutes. You will be asked to roll up your shirt sleeve (if necessary) and the medical professional who will be drawing the blood will swab the area where the needle will be inserted with an alcohol wipe. A rubber tube may be tied around the upper part of your arm, or you may be asked to make a fist, to make the veins stand out more and easier to access.

    A needle attached to a small test tube will be inserted into your vein and blood will begin to flow into the tube. When a sample that is appropriate for the test has been gathered, the needle will be removed, and you may be asked to press on a piece of gauze placed over the insertion site. This pressure will help stop any bleeding from the tiny puncture site. A bandage will then be placed over the site where the needle was inserted.

    Your blood sample will then be sent to lab technicians for analysis. You will receive information when you have the blood test as to when you can expect results.


    Is It Safe?

    Having blood drawn by a qualified medical professional is very safe. You will experience momentary pain when the needle is inserted, and you may experience bruising at the needle insertion site after the test is complete. If you have an allergy to latex or to any adhesives, let the person know who is drawing the blood so he or she can make any necessary adjustments.


    Questions to Ask Your Doctor About Cholesterol and Lipids Tests

    The following questions can help you talk to your physician about having a cholesterol/lipids test. Print out or write down these questions and take them with you to your appointment. Taking notes can help you remember your physician’s response when you get home.

    • Do I need to have an empty stomach before the test? Should I withhold any of my medications? Are there any medications that I will need to take?
    • What happens next if the test shows that my cholesterol/lipids levels are unhealthy?
    • What can I do to have healthier cholesterol/lipids levels?
    • What is my risk level for cardiovascular disease?

     Click here to download and print this list of questions. Take them with you to the doctor and share them with friends and loved ones when you are encouraging them to see their doctors.

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    Cardiac Enzyme Test

    A cardiac enzyme test is one means for assessing if a person is currently experiencing or recently had a heart attack. If you have come to the emergency department with chest pain, cardiac enzymes may be drawn two or three times, several hours apart. It can also be used to check the functioning of the heart after coronary artery bypass graft surgery or angioplasty.


    How Does It Work?

    There are several types of cardiac enzyme tests. These tests can measure blood levels of the enzyme creatine phosphokinase (CPK), also called creatine kinase (CK), and a more specific form of this enzyme called CK-MB. Additionally, cardiac enzyme tests can be used to check blood levels of the proteins myoglobin and troponin. When the heart muscle is damaged, these substances are released from the heart muscle cells into the bloodstream. CPK is also released by other damaged tissues in the body (the brain, for example), so a CPK test must be used in conjunction with symptom evaluation and other tests (possibly including other cardiac enzyme tests) to confirm a heart attack.


    How Is It Performed?

    A cardiac enzyme test is like any other blood test. Having blood drawn typically only takes a few minutes. You will be asked to roll up your shirt sleeve (if necessary) and the medical professional who will be drawing the blood will swab the area where the needle will be inserted with an alcohol wipe. A rubber tube may be tied around the upper part of your arm, or you may be asked to make a fist, to make the veins stand out more and easier to access.

    A needle attached to a small test tube will be inserted into your vein and blood will begin to flow into the tube. When a sample that is appropriate for the test has been gathered, the needle will be removed, and you may be asked to press on a piece of gauze placed over the insertion site. This pressure will help stop any bleeding from the tiny puncture site. A bandage will then be placed over the site where the needle was inserted.

    Your blood sample will then be sent to lab technicians for analysis. You will receive information when you have the blood test as to when you can expect results.


    Is It Safe?

    Having blood drawn by a qualified medical professional is very safe. You will experience momentary pain when the needle is inserted, and you may experience bruising at the needle insertion site after the test is complete. If you have an allergy to latex or to any adhesives, let the person know who is drawing the blood, so he or she can make any necessary adjustments.


    Questions to Ask Your Doctor About Cardiac Enzyme Tests

    The following questions can help you talk to your physician about cardiac enzyme tests. Print out or write down these questions and take them with you to your appointment. Taking notes can help you remember your physician’s response when you get home.

    • Do you think I have had a heart attack?
    • Do the cardiac enzyme test results show that I have had a heart attack?
    • What happens next if I have had a heart attack?

    Click here to download and print this list of questions. Take them with you to the doctor and share them with friends and loved ones when you are encouraging them to see their doctors.

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    C-Reactive Protein (CRP) Test

    A high sensitivity C-reactive protein (HS-CRP) test measures levels of CRP in the bloodstream. CRP is a protein that is released when inflammation is present in the body. Inflammation of the arteries is a risk factor for cardiovascular disease, and CRP may be a predictor of risk for heart attack, stroke, or other cardiovascular problems. An elevated CRP may confer additional predictive value to your other cardiac risk factors.

    A high sensitivity CRP test is better at assessing heart disease than a general CRP test. In either case, inflammation elsewhere in the body can be due to an infection or other illness. Results from an HS-CRP test should be considered in conjunction with symptom evaluation and the results of other tests.


    How Does It Work?

    Your blood will be drawn and sent to a lab for analysis. The amount of C-reactive protein in your blood will be measured. The test results will be communicated back to your physician.


    How Is It Performed?

    A CRP test is like any other blood test. Having blood drawn typically only takes a few minutes. You will be asked to roll up your shirt sleeve (if necessary) and the medical professional who will be drawing the blood will use an alcohol wipe to swab the area where the needle will be inserted. A rubber tube may be tied around the upper part of your arm, or you may be asked to make a fist, to make the veins stand out more and easier to access.

    A needle attached to a small test tube will be inserted into your vein and blood will begin to flow into the tube. When a sample that is appropriate for the test has been gathered, the needle will be removed, and you may be asked to press on a piece of gauze placed over the insertion site. This pressure will help stop any bleeding from the tiny puncture site. A bandage will then be placed over the site where the needle was inserted.

    Your blood sample will then be sent to lab technicians for analysis. You will receive information when you have the blood test as to when you can expect results.


    Is It Safe?

    Having blood drawn by a qualified medical professional is very safe. You will experience momentary pain when the needle is inserted, and you may experience bruising at the needle insertion site after the test is complete. If you have an allergy to latex or to any adhesives, let the person know who is drawing the blood, so he or she can make any necessary adjustments.


    Questions to Ask Your Doctor About C-reactive Protein Tests

     The following questions can help you talk to your physician about a C-reactive protein test. Print out or write down these questions and take them with you to your appointment. Taking notes can help you remember your physician’s response when you get home.

    • Am I at high risk for heart disease?
    • What will the CRP test results tell us about my cardiovascular health?
    • How accurate is a CRP test?
    • What comes next if the test finds inflammation?

     Click here to download and print this list of questions. Take them with you to the doctor and share them with friends and loved ones when you are encouraging them to see their doctors.

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    Genetic Testing

    While all aspects of the medical field are constantly evolving, this is particularly true of genetic testing. Currently genetic tests are available and recommended for a limited number of medical conditions, though more tests become available each year.

    Genetic testing is not recommended to try to assess risk for coronary artery disease, the acquired adult form of heart disease that leads to heart attack. However, if you are an adult who was born with a heart defect (congenital heart disease) and you are interested in having children, genetic testing can help assess the risk of your child inheriting that condition. Genetic tests are not available for all forms of congenital heart disease. Your cardiologist can help you determine if you are a good candidate. 

    Another developing areas in genetic testing is that of identifying patients who may not respond well to certain medications, such as antiplatelet drugs. These patients are called poor metabolizers for that medication - that is, their bodies do not process the medication as would be expected due to genetic variations in the enzyme responsible for processing the medication. Poor metabolizers for certain drugs can be identified through a genetic test. The commonly prescribed antiplatelet medication clopidogrel (Plavix) is one example of a medication for which genetic testing can identify poor metabolizers. The value of genetic testing in a routine fashion to identify poor metabolizers is still unknown.


    How Does It Work?

    A blood sample is sent to a lab where a scientist analyzes the DNA in the blood, which contains genetic information. The scientist looks for information patterns in and around the genes called “markers.” If someone has a particular marker that is known to be associated with a disease, that person should carry a specific gene. Presence of a gene that is associated with a disease only indicates that the person being tested may be predisposed to have that disease. It does not necessarily mean that the person will develop the disease. 

    If you choose to pursue genetic testing, it is important to do so through a validated laboratory in the context of trained genetic counseling and experienced cardiovascular physicians, who can explain the results and place them in the context of your future cardiovascular care.


    How Is It Performed?

    Before you have blood drawn and sent to a lab for analysis, you will meet with a counselor or other medical professional who specializes in genetic testing. During this meeting, you will review your personal and family health histories. This meeting will help determine if, based on the condition you are seeking information about, you are a good candidate for a genetic test. You will also be advised of any limitations of the test.

    The actual genetic test is like any other blood test. Having blood drawn typically only takes a few minutes. You will be asked to roll up your shirt sleeve (if necessary) and the medical professional who will be drawing the blood will swab the area where the needle will be inserted with an alcohol wipe. A rubber tube may be tied around the upper part of your arm, or you may be asked to make a fist, to make the veins stand out more and easier to access.

    A needle attached to a small test tube will be inserted into your vein and blood will begin to flow into the tube. When a sample that is appropriate for the test has been gathered, the needle will be removed, and you may be asked to press on a piece of gauze placed over the insertion site. This pressure will help stop any bleeding from the tiny puncture site. A bandage will then be placed over the site where the needle was inserted.

    Your blood sample will then be sent to lab technicians for analysis. You will receive information when you have the blood test as to when you can expect results.


    Is It Safe?

    Having blood drawn by a qualified medical professional is very safe. You will experience momentary pain when the needle is inserted, and you may experience bruising at the needle insertion site after the test is complete. If you have an allergy to latex or to any adhesives, let the person know who is drawing the blood, so he or she can make any necessary adjustments.


    Questions to Ask Your Doctor About Genetic Tests

    The following questions can help you talk to your physician about a genetic test. Print out or write down these questions and take them with you to your appointment. Taking notes can help you remember your physician’s response when you get home.

    • What will a genetic test tell us about congenital heart disease, drug metabolism, or some other condition?
    • How accurate is the test?
    • Are there any ethical considerations related to the test?
    • Can you refer me to a genetic counselor?

    Click here to download and print this list of questions. Take them with you to the doctor and share them with friends and loved ones when you are encouraging them to see their doctors.

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