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.
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.
1 AnswerA stool analysis (or stool test or stool culture) is a laboratory examination of a sample of feces, or "stool," usually to determine the cause of a problem in the gastrointestinal tract. In a stool analysis, a stool sample is collected in a sterile container. Doctors may order a stool analysis to:
- Have the stool checked for bacteria and/or parasites. This can be done by putting a small amount of the stool on a slide and viewing it under a microscope. In some cases a special stain can be used on the slide to make the organisms easier to see.
- Check the stool for blood, which might indicate bleeding in the gastrointestinal tract or infectious diarrhea.
- Examine the stool for signs of malabsorption problems. For example, fat in the stool may be a sign of certain digestive disorders.
1 AnswerA progesterone test is a laboratory test to measure the amount of progesterone (a hormone made by a woman's ovaries) in the blood. There are several possible reasons a woman may have her progesterone level tested.
- A progesterone test is often part of an infertility workup. A progesterone test can help a doctor determine if and when a woman has ovulated, or if ovulation-inducing medications are working.
- A progesterone test may be ordered early in a pregnancy if the doctor suspects the pregnancy is failing or is ectopic (implanted in a fallopian tube rather than in the uterus).
- Progesterone tests can help a doctor determine the cause of repeated miscarriages in a woman who is experiencing them.
- Progesterone tests are a way to evaluate the placenta and the health of a developing fetus during pregnancy, especially a high-risk pregnancy.
- Progesterone tests can be a way to monitor the effectiveness of progesterone therapy during pregnancy, if a woman is receiving progesterone injections to help support the pregnancy.
- In a non-pregnant woman, a progesterone test may be ordered along with other tests to try to determine the cause of abnormal bleeding from the uterus. High progesterone levels may be an indicator of some forms of cancer, or a problem with the adrenal glands.
1 AnswerA phenylketonuria screening test is one of several screening blood tests that are performed on newborns shortly after birth. This laboratory test screens for a rare, inherited metabolic disorder called phenylketonuria or "PKU." Babies who are born with PKU lack an enzyme called phenylalanine hydroxylase, which is needed to break down the essential amino acid phenylalanine, found in foods that contain protein. When phenylalanine is not broken down, it builds up in the body and can harm the brain and nervous system, leading to developmental problems in the infant.
When PKU is identified early through a phenylketonuria test, the baby can be put on a special diet that is very low in phenylalanine throughout childhood. If the diet is followed strictly, mental damage can be avoided. People with mild cases may be able to resume a normal diet in adulthood, but are often counseled not to.
1 AnswerA Helicobacter pylori test is used to diagnose an infection with the Helicobacter pylori (also known simply as H. pylori) bacterium, and to evaluate the effectiveness of treatment for the infection. H. pylori infections cause no symptoms in some people, but in others they can cause gastritis (inflammation of the stomach lining), stomach and duodenal ulcers and/or may raise a person's risk of developing certain types of cancer, including gastric cancer.
There are several ways to test for H. pylori.
- A stool test. A stool sample is examined in a laboratory to look for traces of H. pylori in the sample.
- A breath test. You drink a liquid containing a low level of a harmless radioactive material that contains urea. If H. pylori is present in your gastrointestinal tract, the bacteria break down the urea into carbon dioxide gas that is detectable in your breath 10-15 minutes later.
- Blood tests are used to measure antibodies to H. pylori. Antibodies are proteins made by the body’s immune system when it detects harmful substances such as bacteria.
- A biopsy. During a procedure called an endoscopy, a small sample of tissue is taken from the stomach lining and examined to look for H. pylori bacteria.
1 AnswerA hair analysis is a laboratory procedure in which a sample of hair, usually taken from the head, is examined to measure the amount of specific substances in the hair. In some cases, a hair analysis can detect the presence of illegal drugs in the hair. Scientists may also examine a hair sample to look for signs of environmental contaminants in the hair. Hair analysis can also be a tool used by forensic scientists who are participating in a criminal investigation.
There are no widely accepted standards that specify how hair samples should be collected, stored and analyzed. Different laboratories use different methods to conduct hair analysis. For this and other reasons, hair analysis alone is not a tool that most doctors or scientists rely on to draw a definitive conclusion or to make a diagnosis. However, hair analysis can be one piece of evidence among others that can help create a picture of someone's health.
1 AnswerA growth hormone test is a laboratory test that measures the level of growth hormone in a sample of your blood. Growth hormone is released by the pituitary gland in the brain. A doctor may order a growth hormone test if a child is unusually large or unusually small for his age, if an adult has unusually large or weak bones or if the doctor suspects a problem with the pituitary gland.
There are two kinds of growth hormone tests -- suppression tests and stimulation tests. Before having your blood drawn for a growth hormone test, your doctor may ask you to fast for 10 to 12 hours, to stop taking all medication and to rest. You will probably have one sample of blood taken immediately after you arrive at the medical facility. If you are having a suppression test, you may be asked to consume a sugary drink, while your blood is taken several more times at set intervals. If you are having a stimulation test, you may receive an intravenous solution of a substance that stimulates the release of growth hormone in your body, and then your blood will be taken at timed intervals.
A normal range for growth hormone in the blood is 1-9 nanograms (ng) per milliliter (mL) of blood in males and 1-16 ng/mL for females.
1 AnswerAn erythrocyte sedimentation rate test, also called an ESR test or a "sed test," is a laboratory blood test that can help determine inflammation in the body that could be associated with certain medical conditions. Those conditions may include some types of cancer, infections and autoimmune diseases, including arthritis and lupus.
The ESR test begins when a medical professional draws a small amount of blood from a vein, usually in your arm. That blood sample is sent to a laboratory for analysis, where the test measures how fast red blood cells (also called erythrocytes) fall to the bottom of a test tube. A faster rate of falling indicates a higher amount of protein than normal in the cells, which indicates the presence of inflammation. Your test results are usually available within a few hours or the next day. Your doctor may order an ESR test if you are experiencing certain symptoms such as joint pain and swelling, unexplained fevers and muscle aches. The ESR test is a screening test and cannot be used to provide a definitive diagnosis of any medical condition.
1 AnswerA chemistry screen is another name for a basic metabolic panel, a group of laboratory blood tests that provide information about your body's metabolism. Usually your doctor will ask you to fast for eight hours and possibly as many as 12 hours before having your blood drawn (typically from a vein in your arm) for this test. A chemistry screen can give your doctor valuable information about:
- how well your kidneys are functioning
- your blood sugar levels
- the acid/base balance of your blood (by checking your levels of carbon dioxide and chloride)
- the amount of calcium in your blood
- the level of a protein called albumin in your blood
- your blood levels of electrolytes including sodium and potassium
- how well your liver is functioning
1 AnswerA CD4 count is a laboratory test that measures how strong a person's immune system is based on the number of a certain type of infection-fighting cell called a CD4 cell in a sample of blood. This test is often ordered to evaluate how well the immune system is working in someone who is newly diagnosed with a human immunodeficiency virus (HIV) infection. HIV is the virus that causes acquired immune deficiency syndrome or AIDS.
A CD4 count may be ordered shortly after a person is first diagnosed with HIV infection as part of a baseline measurement. The CD4 count can be an important tool in deciding the best time to begin treatment with HIV medicines, a regimen known as antiretroviral therapy or ART. A low or falling CD4 count indicates that HIV is advancing and damaging the immune system. A rapidly decreasing CD4 count increases the need to start ART. Once a person has started ART, CD4 counts are usually repeated about every three to six months to monitor how well the therapy is working, or if the person responds very well to ART, testing may be repeated every six to 12 months. A low CD4 count (below 350 cells per cubic millimeter) may indicate infections like thrush or tuberculosis. A count below 200, combined with a positive test for HIV, is considered a sign of AIDS.