Laboratory Testing

Laboratory tests are medical procedures that involve testing samples of blood, urine, or other tissues or substances from the body. The taking of tissue for examination is called a biopsy. (Read about "Biopsy") If you've ever had blood drawn or provided a little cup of urine in your doctor's office, it was most likely for a laboratory test.

Such tests are often used as part of a routine check-up to identify possible changes in a person's health before any symptoms appear. Laboratory tests also play an important role in diagnosis when a person has symptoms. In addition, tests may be used to help plan a patient's treatment, evaluate the response to treatment or monitor the course of a disease over time.

Employers may also use labs to test for employee adherence to certain policies. Labs can detect certain drugs that a person has taken, for instance.

After a sample is taken from your body, it is sent to a laboratory. Laboratories perform tests on the sample to see if it reacts to different substances, according to the Food and Drug Administration (FDA). 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.

Laboratory test samples are analyzed to determine whether the results fall within normal ranges. This is very common in the test most of us have had called a complete blood count. (Read about "Complete Blood Count") FDA says 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. Many factors (including the patient's sex, age, race, medical history and general health) can affect test results. Sometimes, test results are affected by specific foods, drugs the patient is taking, and how closely the patient follows pre-test instructions. That is why a patient may be asked not to eat or drink for several hours before a test. When being tested for diabetes for example, you'll be asked to fast for a few hours before. (Read about "Diabetes") It is also common for normal ranges to vary somewhat from laboratory to laboratory, according to the National Cancer Institute (NCI).

Some laboratory tests are precise, reliable indicators of specific health problems. For example, lab tests can identify bacteria in urine. That can indicate such conditions as urinary tract infections. (Read about "Urinary Tract Infections") Others provide more general information that simply gives doctors clues to possible health problems. Information obtained from laboratory tests may help doctors decide whether other tests or procedures are needed to make a diagnosis. The information may also help the doctor develop or revise a patient's treatment plan. All laboratory test results must be interpreted in the context of the overall health of the patient and are generally used along with other exams or tests. The doctor who is familiar with the patient's medical history and current condition is in the best position to explain test results and their implications.

Lab tests can be administered in many locations. Your doctor can take samples in his office for different types of tests. Some tests may be performed there or they may be sent out to a lab for testing. You may be sent to a local lab where they will take blood, urine or other samples. If you end up in an emergency room (Read about "Emergency Room") or the hospital, they can take samples as well. Almost all hospitals and emergency rooms have access to a laboratory on site for quick testing. That can be a lifesaver. For instance, certain markers show up in your blood if that indigestion is really a heart attack. (Read about "Indigestion" "Heart Attack")

The first laboratory tests of our lives come just after birth. (Read about "Newborn Screenings") A small amount of blood is taken to test for genetic and metabolic diseases. (Read about "Genetics") Many diseases can be treated right away to minimize if not eliminate problems.

Other lab tests involve looking for cancer. (Read about "Cancer: What It Is") Cells from a Pap test for cervical cancer are sent to a lab to look for abnormal cells. (Read about "Cervical Cancer") Likewise, a mammogram that is suspicious can lead to a biopsy with the sample being tested in a lab. (Read about "Mammograms" "Breast Cancer")

Stool samples can reveal things like E. coli, salmonella and other infections. (Read about "E. coli" "Salmonella" "Microorganisms") Blood found in a stool sample by a laboratory may give the first indications of colon cancer. (Read about "Colorectal Cancer")

Labs can test for numerous other diseases and conditions such as STDs, hepatitis, mononucleosis, strep throat, staph and MRSA. (Read about "STDs" "Hepatitis A" "Hepatitis B" "Hepatitis C" "Hepatitis D" "Hepatitis E" "Mononucleosis" "Sore Throat & Strep Throat" "Staph & MRSA") Most of these tests involve taking blood or some sort of swab sample from the patient.

Testing for genetic conditions is also done by more specialized laboratories. Testing for Rh disease is crucial for women who have Rh-negative blood. (Read about "Rh Disease") It can have a serious impact on any babies she may conceive. Other conditions such as Klinefelter syndrome also have a genetic component. (Read about "Klinefelter Syndrome") Some other diseases with genetic components that can be tested for are sickle cell disease, Turner syndrome, fragile X syndrome, Tay-Sachs disease, cystic fibrosis, Huntington's disease and Pompe disease. (Read about "Sickle Cell Disease" "Turner Syndrome" "Fragile X Syndrome" "Tay-Sachs Disease" "Cystic Fibrosis" "Huntington's Disease" "Pompe Disease")

Patients are encouraged to discuss questions or concerns about laboratory test results with their doctor.