Laboratory Tests
What are lab tests?
A laboratory test is a medical procedure in which a sample of blood, urine, or other tissues or substances in the body is checked for certain features. Such tests are often used as part of a routine checkup to identify possible changes in a person’s health before any symptoms appear. Medical laboratory test 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 the disease over time.
Lab test samples are analyzed to determine whether the results fall within normal ranges. They also may be checked for changes from previous tests. 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. It is also common for normal ranges to vary somewhat from laboratory to laboratory.
Some diagnostic laboratory test are precise, reliable indicators of specific health problems. Others provide more general information that simply gives doctors clues to possible health problems. Information obtained from lab 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. Patients are encouraged to discuss questions or concerns about laboratory test results with the doctor.
Why does your doctor use lab tests?
Your doctor uses lab 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?
Lab 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 diagnostic laboratory test 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 medical 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