Laboratory (lab) tests are procedures in which a sample of fluid, tissue or bone is taken from the body and analyzed in a laboratory for signs of diseases. Lab tests are often used to rule out certain disorders associated with symptoms that mimic those of mental illness. In other cases, they may be used to help monitor the effectiveness of a patient’s treatment regimen (e.g., lithium to treat bipolar disorder) or to track the progression of the disease itself.
Although most lab tests are administered by medical professionals in a hospital, clinic or laboratory setting, some tests can be performed by patients in their own homes. Major lab tests that may be used to diagnose and monitor mental health conditions include blood tests and urine tests.
Test results vary from person to person based on a number of factors, including the patient’s gender, age, medical history and general health. Lab test results are only meaningful when compared to established “normal ranges” for that test. These numbers are expressed as a range because the values fluctuate from person to person, and what is considered normal for one person might not be normal for another.
Patients who are scheduled to undergo a lab test should follow any preparatory recommendations suggested by their physician, as some factors are known to potentially influence tests results (e.g., certain foods, vitamins). Patients should report engaging in any activities that deviate from their pre-testing regimen, as failure to closely follow preparatory recommendations can lead to inaccurate test results and a faulty diagnosis.
About lab tests
Laboratory (lab) tests are procedures that analyze fluids, tissue or bone in the body to detect signs of illnesses. They may be performed during a routine checkup to look for illnesses before symptoms occur, or as part of an examination to locate the source of symptoms.
Lab tests are frequently used to rule out certain disorders associated with symptoms that mimic those of mental illness. For example, a child who appears to have autism may undergo certain lab tests (e.g., blood tests, urine tests), among other procedures, to ensure that the symptoms are not caused by another underlying condition. Or, a patient who has symptoms of depression may undergo blood testing to look for the presence of a viral infection, which sometimes causes similar symptoms. In addition, other medical causes for a mental health disorder, such as dementia, may be ruled out with lab tests.
Lab tests are also used to help detect signs of a mental illness. For example, blood testing can reveal nutritional inadequacies that may indicate the presence of an eating disorder. Blood tests, urine tests, saliva tests, sweat tests and hair analysis can also detect use of alcohol and other substances.
In addition, lab tests may be used to monitor the level of certain medications in the blood (e.g., lithium to treat bipolar disorder) or to track the progression of the disease itself.
Most lab tests take place in a clinic, hospital or laboratory setting. However, some samples can be taken in the patient’s home. After a sample of fluid or tissue is obtained, it is sent to the laboratory for analysis. In some cases, a sample may be compared to an earlier sample to see how the patient’s condition has changed over a period of time.
The two types of lab tests most commonly ordered by physicians include:
- Blood tests. Detect abnormally high or low levels of substances in blood that may indicate a variety of conditions. These tests can be used to screen for a disease before signs and symptoms appear, help determine a diagnosis, monitor the progression of a disease and monitor the effectiveness and safety of a patient’s treatment.
Depending on the nature of the test, blood samples may be obtained by inserting a needle into the skin (e.g., a finger) for a small sample, or into a vein or artery for a larger sample. Blood tests can be performed on different parts of the blood, including whole blood (blood that has not been separated into its many components), blood plasma (the liquid part of the blood), blood serum (plasma that has had the clotting agent removed) or blood cells (the individual red blood cells, white blood cells and platelets).
- Urine test. Also known as a urinalysis, this test uses a sample of urine to diagnose diseases of the urinary system and other body systems. Urinalysis may be ordered to check for early signs of a disease or disorder, or it may be used to monitor kidney or liver diseases. Urine tests typically are performed in physician offices, clinics, hospitals or laboratories.
There are many kinds of urine tests that can be used to detect infection, to monitor various illnesses and to diagnose complications.
Blood and urine samples can also be used to detect abused substances and alcohol.
In some cases, patients may also be given a fecal occult blood test (FOBT), which uses a chemical process to detect hidden (occult) blood in a person’s stool. The presence of such blood may result from inflammatory disorders, infections, vascular problems or tumors. Use of certain medications – including nonsteroidal anti-inflammatory drugs (NSAIDs), antibiotics and anticoagulants – can also cause this type of bleeding.
Types of blood tests
There are a variety of blood tests that can be performed to look for illness. Common types include:
- Basic metabolic panel (BMP). A group of tests often ordered in hospital emergency rooms because the components provide important information about the status of a patient’s kidneys, electrolyte and acid/base balance. They also reveal a patient’s glucose (blood sugar) levels. Significant changes in these test results can indicate acute conditions, such as kidney failure, insulin shock or diabetic coma, respiratory distress, or heart rhythm changes.
- Complete blood count (CBC). Measures the number of red blood cells, white blood cells and platelets in a patient’s blood. It also detects the amount of hemoglobin (a substance that carries oxygen throughout the body) in the red blood cells and a number of other factors. Patients who take medications that affect the CBC must have periodic blood testing for monitoring.
- Differential. Also called white blood cell count (WBC), it measures the numbers of white blood cells in a blood sample. This test also includes information about abnormal cell structure and the presence of immature cells. A patient’s WBC may increase as a result of infection (e.g., appendicitis) or decrease with use of certain medications or in response to certain diseases. In addition, a low WBC indicates that a patient may be at higher risk for infections.
- Complement. Measures the blood levels of proteins (complement) that help destroy foreign substances in the body. This type of blood test is also useful in evaluating kidney damage and in monitoring the progression of a disease.
- Sedimentation rate (sed rate). Measures the rate at which red blood cells (erythrocytes) separate from the liquid part of blood (plasma) and fall to the bottom of a test tube, forming sediment. Higher sed rates indicate the presence of inflammation somewhere in the body.
- Electrolyte panel. Measures the body’s main electrolytes (sodium, potassium, chloride and carbon monoxide) to help determine whether or not the body has a proper fluid balance.
- Renal function tests. A group of blood tests that measure the levels of specific waste products in a patient’s blood sample. They commonly test for uric acid, creatinine and blood urea nitrogen (BUN). When the kidneys are not working properly, waste products can build up in the body.
- Enzyme tests. A group of blood tests that measure enzyme (protein required for chemical reactions to take place in cells) levels in the blood. These tests assess how well the body’s systems are functioning and whether any tissue damage has occurred.
- Antibody tests. Blood tests are available for many antibodies, substances produced by the body to fight specific infections. The presence of some antibodies are general indicators of inflammation somewhere in the body. Other antibodies may more specifically indicate diseases.
- Thyroid function tests. A group of blood tests that evaluate how the thyroid is functioning. Symptoms of mental disorders (e.g., sleep disorders, depression) may be initially attributed to thyroid abnormalities.
Types of urine tests
Common types of urine tests used to detect various illnesses include:
- Uric acid test. Uric acid is the end product of the breakdown of nucleotides as a normal part of metabolism. In conjunction with urinalysis of other waste products, it can be used to assess how well the kidneys are functioning.
- Creatinine test. Measures the amount of creatinine in the urine. Creatinine is a waste product removed from the body by the kidneys. Abnormal amounts of creatinine may be a sign of kidney damage.
- Bilirubin test. Measures the amount of bilirubin – an orange-yellow waste product made from damaged or old red blood cells that have died – in the urine. Bilirubin is not normally detected in the urine. Excessive amounts of bilirubin can cause jaundice (yellowing of the skin and the whites of the eyes). The presence of bilirubin in the urine is often a sign of liver or gallbladder dysfunction.
- Urine specific gravity test. Measures the concentration of particles in the urine. Abnormally increased or decreased urine specific gravity may indicate a kidney disorder.
- White blood cell test. Checks urine for the presence of white blood cells. The main infection-fighting cells in the body, white blood cells are not normally detectable in the urine. The presence of white blood cells in the urine may indicate a urinary tract infection.
Factors that may affect lab test results
Patients who are scheduled to undergo a laboratory (lab) test should follow any preparatory recommendations suggested by their physician, as some factors are known to potentially influence tests results. The physician may instruct patients to make changes to their diet or to stop taking certain medications, vitamins and supplements. In some cases, patients may be asked to restrict exercise or to modify sexual activity.
In some cases, patients who undergo fecal testing may have a false-positive or false-negative reading. For this reason, fecal tests are often performed in conjunction with another test to ensure an accurate diagnosis.
Patients should report engaging in any activities that deviate from their pre-testing regimen. Honesty is important – failure to closely follow a physician’s preparatory recommendations can lead to inaccurate test results, which may, in turn, lead a physician to suggest ineffective or unnecessary treatments.
Test results also vary from person to person based on a number of other factors, including the patient’s gender, age, medical history and general health.
Understanding lab test results
Laboratory (lab) tests results are only meaningful when compared to established “normal ranges” for that test. These numbers are expressed as a range because the values fluctuate from person to person, and what is considered normal for one person might not be normal for another.
The range of values considered to be normal is the range of test results from the samples of normal, active, healthy people.
When a person has a disease or health problem, their test results may be higher or lower than normal – or “outside of the normal range.” When a physician sees that a test result is outside of the normal range, the test may be repeated to verify results or additional tests may be ordered to determine the underlying cause(s) of the abnormality. Imaging tests (e.g., x-ray, CAT scan or MRI) and tissue biopsy are examples of tests that may also be performed.
Normal ranges for some tests may vary slightly from lab to lab. For example, results of blood tests that are performed by machine in one lab are likely to differ from results of tests performed by hand in another lab. Frequently, results of a patient’s test are compared to another sample taken from a healthy individual that is run at the same time and is designated as the “normal control.” When the “normal control” sample falls within the normal range, or reaches a specific “known” measurement, the laboratory results confirm that the test has been carried out accurately.
Frequency of lab testing
The frequency of lab testing will depend upon the circumstances of the patient’s illness. Typically, testing continues on a regular schedule if the laboratory tests are being used to monitor the progression of the patient’s illness or the effectiveness of a patient’s treatment regimen.
Questions for your doctor regarding lab tests
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to laboratory (lab) tests:
- Why is a lab test appropriate for me?
- What type of lab test do I need?
- What will you be looking for?
- Will the procedure take place in an office, or can I collect the sample at home?
- Do I need any preparations before the sample collection, such as fasting?
- Does the sample need to be collected at a specific time?
- Do you need more than one sample?
- What kind of conditions can be diagnosed with this lab test?
- Who will analyze my sample?
- When can I expect to receive the results of the test?