Doctor-Reviewed Health Guides: Conditions, Procedures & Health News

A reticulocyte count measures how many immature red blood cells (reticulocytes) are in the blood, showing whether the bone marrow is making enough new ones. A normal result is 0.5% to 2.5% in adults and 2% to 6% in infants. A low count may point to a marrow problem; a high count to blood loss or hemolytic anemia.

Your blood oxygen level (blood oxygen saturation) is the amount of oxygen circulating in the blood. For most people, a normal pulse oximeter reading is 95% to 100%. At home, call your provider if your reading is 92% or lower, and go to the nearest emergency room if it is 88% or lower.

A tilt table test, also called head-up tilt table (HUTT) testing, helps find out why you faint. You lie strapped to a padded table that quickly moves you from flat to nearly upright while monitors track your blood pressure, heart rate and heart rhythm. It can help diagnose vasovagal syncope, postural orthostatic tachycardia syndrome (POTS) and orthostatic hypotension.

Cardiac output is how many liters of blood your heart pumps in one minute. It equals stroke volume (blood pumped per beat) multiplied by heart rate. A normal cardiac output is 5 to 6 liters per minute at rest. Providers measure it to look for problems such as heart failure or to check whether a treatment is working.

A Coombs test is a blood test that checks for antibodies that can attack red blood cells. The direct Coombs test looks for antibodies stuck to red blood cells and helps diagnose autoimmune hemolytic anemia. The indirect Coombs test looks for antibodies in the bloodstream and is used before blood transfusions and during pregnancy. A negative result is normal.

A physical exam is a checkup of your overall health done by a primary care provider. The provider checks your vital signs, height and weight, reviews your medical history and medicines, and examines your body. It focuses on prevention: updating vaccines and looking for underlying conditions. Most providers recommend one every year, and it takes about 30 minutes.

A urine protein test measures how much protein is in the urine. A higher level, called proteinuria, can be a sign that the kidneys aren't working well. The normal amount is less than 150 milligrams per day. High protein can be temporary, from dehydration, exercise or a UTI, or point to kidney disease.

Right heart catheterization is an invasive test that shows how well the heart is pumping. A cardiologist guides a thin, flexible catheter from a vein through the right side of the heart into the pulmonary artery, then measures blood pressure and oxygen in the heart and lungs. It helps diagnose and manage pulmonary hypertension and heart failure.

An appendicitis test isn't a single test: providers combine a physical exam, blood and urine tests, and imaging to confirm appendicitis. A CT scan is the most accurate, while ultrasound avoids radiation and is used for children and pregnant people. Appendicitis is an emergency, so seek care right away for constant belly pain.

Tinel's sign is a tingling or pins-and-needles feeling you get when a provider taps your skin over a nerve. A positive sign may mean the nerve is compressed or damaged at that spot, as in carpal tunnel, cubital tunnel or tarsal tunnel syndrome. The test is quick, painless and has no risks, and you know the result right away.

A nuclear stress test is a heart imaging test that shows how well blood flows to the heart muscle at rest and under stress. A radioactive tracer is injected, and a camera takes pictures before and after exercise. Areas with poor blood flow can point to coronary artery disease or damage from a past heart attack.

A thyroid ultrasound is a quick, painless imaging test that uses sound waves to show pictures of the thyroid and the tissue around it. It helps diagnose goiter, thyroid nodules and thyroid cancer, although it can't diagnose cancer by itself. It takes about 30 minutes and has no risks.

A bladder ultrasound is a painless imaging test that uses sound waves to create pictures of the bladder. Providers use it to find bladder stones and tumors, check the size, shape and thickness of the bladder, and see how much urine it holds and whether it empties completely. The scan takes less than 30 minutes and has no risks.

Neuropsychological testing is a set of paper, puzzle and computer tasks that shows how well the brain handles thinking, memory, language, attention, mood and behavior. Providers use it to sort out the cause of memory or thinking problems and measure strengths and weaknesses after a brain injury or stroke. The tests take several hours, and you receive a written report.

An MRA (magnetic resonance angiography) is a type of MRI scan that creates detailed pictures of the arteries, veins and the blood flowing through them. A provider may order it to look for narrowed, widened or blocked blood vessels, such as an aneurysm or a buildup of plaque. It takes 20 to 60 minutes and uses no radiation.

Cancer staging is a way for a care team to describe how big a cancer is and how far it has spread, while grading describes how abnormal the cancer cells look under a microscope. Staging is based on a physical exam and tests such as imaging, a biopsy and blood tests. It helps plan treatment and estimate outlook.

A globulin blood test measures globulins, a group of proteins your liver and immune system make. A normal globulin level is about 2.0 to 3.5 g/dL. High levels can point to autoimmune disease, infection, inflammation or cancers such as multiple myeloma, while low levels can be a sign of liver or kidney disease.

An antinuclear antibody (ANA) test is a blood test that looks for antibodies that target the nucleus of your own cells. It helps providers check for autoimmune diseases such as lupus, Sjögren's syndrome and scleroderma. A positive result does not mean you have an autoimmune disease: up to 3 in 10 people without one test positive.

Chorionic villus sampling (CVS) is an optional prenatal test that collects a sample of cells from the placenta to check the fetus for chromosomal and genetic conditions, such as Down syndrome. It's done between weeks 10 and 13 of pregnancy and takes less than 30 minutes. The test is about 99% accurate at showing whether a condition is present.

Laryngoscopy is a procedure that lets a throat specialist look at the larynx, or voice box, with a lighted scope and camera. It finds the cause of speaking or swallowing problems and checks for laryngitis, growths or cancer. A flexible scope passes through the nose in an office visit; a direct scope goes through the mouth under anesthesia.

A myoglobin test measures how much myoglobin, an oxygen-carrying protein found in the heart and skeletal muscles, is in blood or urine. Providers use it to look for recent muscle damage and check for heart, kidney and muscle conditions. A normal blood level is usually under 72 ng/mL, and myoglobin normally does not show up in urine.

An endoscopic ultrasound (EUS) is a procedure that combines an endoscope, a flexible tube with a light and camera, with an ultrasound probe. It lets a gastroenterologist see the digestive tract and nearby organs such as the pancreas, gallbladder and bile ducts, and it can guide a needle biopsy. It's an outpatient procedure done under sedation.

A concussion test is a set of questions, symptom checklists and simple tasks that check how the brain is working after a bump, blow or jolt to the head. It looks at alertness, memory, attention, vision, balance and coordination. It's only one part of the diagnosis: a provider also does a full exam and may order imaging.

A chest X-ray, also called a chest radiograph or CXR, is a quick, noninvasive imaging test that makes pictures of your heart, lungs and bones. It helps providers find problems such as pneumonia, emphysema, COPD, heart failure and broken ribs. The test takes a few minutes, and nonemergency results usually come back in one to two days.