Laboratory Tests
What are lab tests?
Laboratory tests are medical procedures that involve testing samples of blood, urine, or other tissues or substances in the body.
Why does your doctor use lab tests?
Your doctor uses laboratory tests to help:
- Identify changes in your health condition before any symptoms occur
- Diagnose a disease or condition before you have symptoms
- Plan your treatment for a disease or condition
- Evaluate your response to a treatment, or
- Monitor the course of a disease over time.
After your doctor collects a sample from your body, it is sent to a laboratory. Laboratories perform tests on the sample to see if it reacts to different substances. Depending on the test, a reaction may mean you do have a particular condition or it may mean that you do not have the particular condition. Sometimes laboratories compare your results to results obtained from previous tests, to see if there has been a change in your condition.
What do lab tests show?
Laboratory tests show whether or not your results fall within normal ranges. Normal test values are usually given as a range, rather than as a specific number, because normal values vary from person to person. What is normal for one person may not be normal for another person.
Some laboratory tests are precise, reliable indicators of specific health problems, while others provide more general information that gives doctors clues to your possible health problems. Information obtained from laboratory tests may help doctors decide whether other tests or procedures are needed to make a diagnosis or to develop or revise a previous treatment plan. All laboratory test results must be interpreted within the context of your overall health and should be used along with other exams or tests.
What factors affect your lab test results?
Many factors can affect test results, including:
- sex
- age
- race
- medical history
- general health
- specific foods
- drugs you are taking
- how closely your follow preparatory instructions
- variations in laboratory techniques
- variation from one laboratory to another
Blood tests usually can be done in a doctor's office or in a lab where technicians are trained to take blood. When only a small amount of blood is needed, the sample can sometimes be taken from a baby by sticking a heel and from an older child by sticking a finger with a small needle.
If a larger blood sample is needed, the technician drawing the blood will clean the skin, insert a needle into a vein (usually in the arm or hand), and withdraw blood. In kids, it sometimes takes more than one try. A bandage and a cotton swab will help dry any blood left when the needle is removed.
Blood tests can be scary for kids, so try to be a calming presence during the procedure. Holding your child's hand or offering a stuffed animal or other comforting object can help. Tell your child that it may pinch a little, but that it will be over soon. With younger kids, try singing a song, saying the alphabet, or counting together while the blood is being drawn.
Common blood tests include:
- Complete Blood Count (CBC). A CBC measures the levels of different types of blood cells. By determining if there are too many or not enough of each blood cell type, a CDC can help to detect a wide variety of illnesses or signs of infection.
- Blood Chemistry Test. Basic blood chemistry tests measure the levels of certain electrolytes, such as sodium and potassium, in the blood. Doctors typically order them to look for any sign of kidney dysfunction, diabetes, metabolic disorders, and tissue damage.
- Blood Culture. A blood culture may be ordered when a child has symptoms of an infection — such as a high fever or chills — and the doctor suspects bacteria may have spread into the blood. A blood culture shows what type of germ is causing an infection, which will determine how it should be treated.
- Lead Test. The American Academy of Pediatrics (AAP) recommends that all toddlers get tested for lead in the blood at 1 and 2 years of age since young kids are at risk for lead poisoning if they eat or inhale particles of lead-based paint. High lead levels can cause stomach problems and headaches and also have been linked to some developmental problems.
- Liver Function Test. Liver function tests check to see how the liver is working and look for any sort of liver damage or inflammation. Doctors typically order one when looking for signs of a viral infection (like mononucleosis or viral hepatitis) or liver damage from other health problems.
Informations obtained from National Institute of Health.