Lab Tests

Lab Tests

Lab Tests
Lab tests are performed to check the health of a patient. Blood, urine and other substances are performed to diagnose, treat or prevent the onset of conditions and diseases.

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    DNA fingerprinting is a type of laboratory analysis used to match a sample of biological material (such as blood, hair, skin, saliva or semen) from an unknown source to a sample from a known source. Also called DNA typing or DNA analysis, DNA fingerprinting can be used to establish paternity, or to identify the remains of a missing person, or to establish a link between biological evidence left behind at a crime scene and a suspect in the criminal investigation. It can also be used to exonerate a suspect if there is no DNA match.

    DNA (deoxyribonucleic acid) is the genetic material present in almost all of your cells. DNA comprises two strands that contain complementary genetic information. A gene is a segment of DNA that is passed down from parents to children and confers a trait to the offspring. Genes are organized and packaged in units called “chromosomes.” Humans have 23 pairs of chromosomes. Each pair of chromosomes is comprised of one contribution from your mother and the other from your father.

    Identical twins have 100 percent of the same DNA. Any other two people share, on average, 99.9% of their DNA. That means only 0.1% of your DNA is unique to you. In DNA fingerprinting, laboratory scientists look for the presence of repeated sequences within the DNA,which are present in all individuals on different chromosomes and are known to vary from individual to individual (except for identical twins). These sequences can act as genetic markers to identify an individual.
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    Liver function tests are blood tests that help your doctor determine how well your liver is functioning and whether there are any signs of injury, infection or disease in your liver. Your doctor may order liver function tests -- also called a "liver panel" -- as part of a routine checkup or if you have signs of a potential liver problem or are at risk for liver disease. If you are being treated for liver disease, your doctor may order liver function tests to determine how well that treatment is working.

    Some liver function tests check the levels of certain enzymes that are essential to chemical reactions that help the liver function normally. These tests include:
    • Alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These enzymes are involved in processing proteins. Too high levels of ALT and/or AST can signal that the liver is injured or damaged.
    • Alkaline phosphatase (ALP). ALP levels that are higher than normal can be a sign of liver diseases,blocked bile ducts, or other conditions.
    • Gamma-glutamyl transpeptidase (GGT) is an enzyme found in large amounts in your liver, bile ducts and pancreas. High levels of GGT in the blood may signal liver or bile duct damage.
    Other liver function tests check the blood levels of certain substances needed for normal liver functioning. These tests include:
    • Bilirubin tests. Bilirubin is a byproduct of the normal breakdown of red blood cells. If your liver is damaged, bilirubin can leak out of your liver into your blood, causing your skin and eyes to appear yellow (jaundice).
    • Globulin and albumin are proteins made in the liver. Low levels of these proteins may indicate liver damage.
    • An alpha-1 antitrypsin test measures the amount of a protein that helps protect the liver (and the lungs) from damage. A deficiency in alpha-1 antitrypsin may signal a rare form of cirrhosis. An alpha-1 antitrypsin deficiency can be inherited.
    • Prothrombin time (PT) test. Prothrombin is a protein made in your liver that helps with normal blood clotting. A prothrombin time test measures how long it takes for the liquid portion of your blood (plasma) to clot. A high prothrombin time can be a sign of liver damage.
    If your doctor orders liver function tests, you may need to fast overnight before you give a blood sample. Follow your doctor's directions exactly to help ensure accurate test results.
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    Are recurrent breast cysts a cause of concern?
    Recurrent breast cysts can cause pain and stress in women. In this video, Darcy Bryan, MD, of Riverside Community Hospital, explains the concerns with cysts that keep coming back. 
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    There are times that the hemoglobin A1c result does not accurately reflect a person’s average blood glucose readings. Hemoglobin A1c is created when glucose in the blood comes into contact with the hemoglobin inside a red blood cell. When a red blood cell is first created in the bone marrow, there is no hemoglobin A1c. As the cell circulates in the bloodstream over its life expectancy of about 4 months, hemoglobin A1c accumulates to a greater and greater degree. The oldest cells -- the ones that are closest to the end of their life cycle -- have the highest amount of hemoglobin A1c. Therefore, the amount of hemoglobin A1c in the blood varies depending not only on how much glucose there is in the system, but also on the rate of production of red blood cells, the rate of destruction of those cells, the average life span of a red blood cell, and factors that may affect the rate at which glucose attaches to the hemoglobin. 

    The hemoglobin A1c usually underestimates the average glucose in the blood in settings in which red blood cells do not survive as long as they should in the blood. A simple example might be if someone has major blood loss, such as following an accident or surgery. Assume that the person has lost a fair amount of blood, but not enough to need a transfusion. In this case the bone marrow revs up to replace the lost blood at a faster rate than normal, and a higher percentage of the red cells are relatively young, with little hemoglobin A1c in them. This results in a lower hemoglobin A1c than would be expected for the glucose level.

    The opposite situation occurs in people with sickle cell disease. People with sickle disease have an abnormal form of hemoglobin in their blood -- hemoglobin S -- instead of the normal hemoglobin A. Hemoglobin S causes the red blood cells to assume a sickle or crescent shape in some settings. But hemoglobin S has another characteristic, which is that it combines with glucose to form hemoglobin A1c at a faster rate than normal hemoglobin A. Therefore, people with sickle disease will have a hemoglobin A1c that overestimates their average glucose levels and will make their diabetes look more poorly controlled than it actually is. This is true also of people with sickle trait, though to a lesser degree because they have lower levels of hemoglobin S. 
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    pH is a scale from 0 to 14 that measures how acidic or basic a substance is. A pH less than seven is acidic. A pH greater than 7 is basic. Seven on the pH scale is neutral.

    For example, lemonade a drink high in citric acid, has a pH of about 2.2 to 3. Ammonia is basic and has a pH of about 11 to 12. Pure water has a neutral pH of 7.
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    A urine pregnancy test is a chemical test that detects the presence of a hormone called human chorionic gonadotropic or HCG, which is produced in a woman's body during pregnancy. Many urine pregnancy tests are at-home tests that require a woman to urinate on a test strip or to collect urine in a sterile sample cup and either dip a test strip into the urine or place a few drops of urine from the cup onto a test stick.

    Most urine pregnancy tests suggest waiting at least two minutes before reading the result. A urine pregnancy test is positive if HCG is detected in the urine. Depending on the test, a positive result may cause a line to appear or a plus sign or other change in the test strip.

    Urine pregnancy tests have about a 99 percent accuracy rate when used according to directions. They may be able to detect a pregnancy as early as 10 days after conception, but most tests recommend taking the test after a missed menstrual period. Using your first urine in the morning is also sometimes recommended as HCG concentration may be higher at that time.

    If you have a positive result on a urine pregnancy test, call your doctor, who may want to follow up with a pregnancy test on your blood, which can detect not only whether HCG is present but how much, which can give clues to the health of your pregnancy.
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    A urine culture is a laboratory test that examines a urine sample for bacteria or other germs. Urine cultures are performed commonly to determine if someone has a urinary tract infection.

    Common symptoms of a urinary tract infection include:
    • frequently feeling that you need to urinate, but not producing much urine when you do urinate
    • feeling pain or burning when you urinate
    • abdominal pain
    • fever
    If you experience these symptoms your doctor will likely ask you to urinate into a sterile sample cup. That cup will then be sent to a lab for analysis and the results should be ready in one to three days.

    If bacteria is present in your urine in high amounts you have a positive test which means you have a urinary tract infection. Your doctor may treat you with medication, including antibiotics. If your test comes back negative but your symptoms persist, your doctor may want to repeat the urine culture in a day or two.
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    A toxoplasmosis test is a laboratory blood test to detect a current or past infection with a parasite called toxoplasma gondii. If you are infected with this parasite, your body's immune system produces antibodies to fight it. The toxoplasmosis test looks for and measures the level of those antibodies. Toxoplasma gondii is especially dangerous in people who have weak or compromised immune systems (such as people who have AIDS) or in pregnant women. If a pregnant woman develops antibodies during pregnancy detected by the toxoplasmosis test, the doctor may order a test on the amniotic fluid to determine the risk to her developing baby. The toxoplasma gondii parasite is transmitted from raw or undercooked meat, by consuming contaminated food or water, or by handling cat litter (since cat feces is a carrier of the parasite).
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    A toxicology screen is a group of laboratory tests that are performed to detect drug abuse (including alcoholism), to monitor someone who has a drug abuse problem, or to evaluate drug intoxication, poisoning or overdose. Toxicology screens typically analyze blood or urine, but may also involve the examination of stomach contents obtained by suctioning out the contents through a process called gastric lavage or from vomiting.

    Toxicology screens may be ordered as part of a screening process for a new job, randomly as part of workplace or athletic program drug testing. It may also be done in an emergency room for medical and/or legal purposes to determine the drugs that someone might have ingested.

    For accuracy, toxicology screens typically need to be done within a certain amount of time after a drug is ingested. This time period varies, depending upon the drug in question. For example, screening for alcohol usually needs to be done three to ten hours after ingestion; screening for cocaine can be done as much as four days after ingestion.
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    A throat culture test is a laboratory test that is performed to identify the cause of a sore throat, most commonly to see if someone has strep throat. Before ordering a throat culture test, your doctor will first rub a sterile cotton swab along the back of your throat near your tonsils. That cotton swab will then be sent to a laboratory where it will be put on a special plate to allow any bacteria on the swab to grow. The laboratory technician can then examine the swab for signs of bacteria, and usually can provide results within one to three days. A positive throat culture for strep throat means the swab was found to contain group A streptococci, the bacteria that causes strep throat. (Less commonly, sore throats may be caused by group C or group G streptococci.) Your doctor may prescribe antibiotics to help clear up the infection. A negative throat culture means you do not have strep throat, but more likely a viral infection that is causing your sore throat that will likely resolve on its own.