Testing Knowledge
Test Directory
Source-backed test guides: what each test is for, how it is performed, its limitations, and which reviewed products serve it. Personal health questions are answered with knowledge and preparation guidance — not supplier sales.
Tricyclic Antidepressant (TCA) Screen
This test checks whether tricyclic antidepressants (TCA) can be found in your blood or urine. It can also measure how much TCA is in your blood or urine. TCAs are a type of antidepressant . Antidepressants are prescription medicines that treat depression , a serious mood disorder . Depression can affect how you think, feel, and behave.
TP53 Genetic Test
A TP53 genetic test uses a sample of your blood, bone marrow, or tissue from a tumor to look for changes in the tumor protein 53 gene, or TP53 for short. Changes in your genes are also called gene variants or mutations.
Total Protein and Albumin/Globulin (A/G) Ratio
A total protein and albumin/globulin (A/G) ratio test measures the total amount of protein in your blood. Proteins have many important functions, including giving your body energy, rebuilding muscles, and helping your immune system . Your body might make too much or too little protein if you have certain health conditions.
Thyroxine (T4) Test
Thyroxine is also called T4. T4 is a hormone that your thyroid gland makes. A T4 test measures the level of T4 in a sample of your blood. Too much or too little T4 may be a sign of a thyroid problem .
Thyroid Antibody Tests
A thyroid antibody test measures the level of thyroid antibodies in a sample of your blood to check for an autoimmune thyroid disease . Your thyroid is a small, butterfly-shaped gland in your neck. It makes hormones that control many activities in your body, including your heart rate and how fast you burn calories from food.
Thyroglobulin
A thyroglobulin test measures the amount of a protein called thyroglobulin (Tg) in a sample of your blood. Your thyroid (a small, butterfly-shaped gland in your neck) makes thyroglobulin along with many other important hormones . Together, these hormones control bodily activities such as your heart rate and how fast you burn calories from food.
Therapeutic Drug Monitoring
Therapeutic drug monitoring (TDM) is testing that measures the amount of certain medicines in your blood. It checks whether the amount of medicine you take is safe and effective.
Testosterone Levels Test
A testosterone levels test measures the amount of the hormone testosterone in a sample of your blood. Hormones are chemical messengers in your bloodstream that control the actions of certain cells or organs.
Syphilis Tests
Syphilis tests generally look for certain antibodies in your blood. Antibodies are proteins that your immune system makes when it finds harmful substances in your body. In this case, the harmful substance is the bacterium that causes syphilis , one of the most common sexually transmitted infections (STIs.)
Stool Elastase Test
A stool elastase test measures the amount of elastase in your stool (poop). Elastase is a type of digestive enzyme, a protein that speeds up certain chemical reactions in your body. The pancreas, a gland that sits behind your stomach, makes these digestive enzymes to help your body break down food and absorb nutrients. Your body can then use these nutrients for energy, growth, and repairing cells.
Sputum Culture
A sputum culture is a test that checks for bacteria or another type of germ that may be causing a respiratory tract infection (an infection in your lungs or airways). Sputum, also known as phlegm, is a thick type of mucus made in your lungs. If you have an infection or chronic illness affecting the lungs or airways, sputum can settle in your lungs, and you may also cough it up
Sodium Blood Test
A sodium blood test measures the amount of sodium in your blood. Sodium is a type of electrolyte . Electrolytes are minerals that have an electrical charge when they are dissolved in water or body fluids. You have electrolytes in your blood, urine (pee), tissues, and other body fluids. They help control the amount of fluid and the balance of acids and bases (pH balance) in your body. Sodium also helps your nerves and muscles work properly.
Smooth Muscle Antibody (SMA) Test
This test looks for smooth muscle antibodies (SMAs) in a sample of your blood. High levels of SMAs are usually a sign of a chronic (long-lasting) liver condition called autoimmune hepatitis .
SHBG Blood Test
An SHBG blood test measures the level of a protein called sex hormone binding globulin (SHBG) in a sample of your blood. SHBG is made mostly in your liver. It binds (attaches) to sex hormones such as testosterone and estrogen and helps control how much of these hormones are active in your body.
Salicylates Level
This test measures the amount of salicylates in the blood. Salicylates are a type of drug found in many over-the-counter and prescription medicines. These can include:
Rheumatoid Factor (RF) Test
A rheumatoid factor (RF) test checks a sample of your blood for rheumatoid factor, a protein made by the immune system .
Reticulocyte Count
A reticulocyte count (retic count) measures the number of reticulocytes in your blood. Reticulocytes are immature (still developing) red blood cells (RBCs). Your body makes reticulocytes in your bone marrow. Then it sends them into your blood, where they mature into red blood cells within one to two days. The main job of the red blood cells is to move oxygen from your lungs to every cell in your body.
Respiratory Syncytial Virus (RSV) Tests
RSV stands for respiratory syncytial virus. It is a viral infection that affects the respiratory tract. Your respiratory tract includes your lungs, nose, and throat. RSV testing checks a fluid sample from your nose to see if the virus is in your body and causing symptoms of a respiratory infection.
Renin Test
This test measures the level of renin in your blood. Renin is an enzyme, a protein that speeds up certain chemical reactions in your body. It's made by your kidneys. When your blood pressure or sodium decreases or your potassium increases, your kidneys release renin. That's because renin also acts as a hormone (a chemical messenger in your bloodstream that controls the actions of certain cells or organs) to help control your blood pressure.
Red Blood Cell Antibody Screen
An RBC (red blood cell) antibody screen is a blood test that looks for RBC antibodies in your blood. These antibodies destroy red blood cells that are foreign (different from your own).
Red Blood Cell (RBC) Indices
Red blood cell (RBC) indices measure your red blood cells' size, shape, and quality. Red blood cells are also known as erythrocytes. They are made in your bone marrow (the spongy tissue inside your large bones). They contain hemoglobin, an iron-rich protein in your red blood cells that carries oxygen from your lungs to every cell in your body. Your cells need oxygen to grow, reproduce, and make energy.
Red Blood Cell (RBC) Count
A red blood cell (RBC) count measures the number of red blood cells, also known as erythrocytes, in your blood. Red blood cells are made in your bone marrow, the spongy tissue inside your large bones. They contain hemoglobin, an iron-rich protein that carries oxygen from your lungs to every cell in your body. Your cells need oxygen to grow, reproduce, and make energy for you to function. An RBC count that is higher or lower than normal is often the first sign of an illness. So, the test may allow you to get treatment even before you have symptoms.
RDW (Red Cell Distribution Width)
A red cell distribution width (RDW) test measures how much the volume and size of your red blood cells (erythrocytes) varies.
PTEN Genetic Test
A PTEN genetic test uses a sample of your blood or other body tissue to look for changes in a gene called PTEN . Changes in your genes are also called gene variants or mutations.