Common Tests

Information on medical tests, including how to prepare, what to expect, and what the results mean.

 

BLOOD TESTS


Cholesterol and Triglycerides Tests

Test Overview

Cholesterol and triglyceride tests are blood tests that measure the total amount of fatty substances (cholesterol and triglycerides) in the blood.
Cholesterol travels through the blood attached to a protein. This cholesterol-protein package is called a lipoprotein. Lipoprotein analysis (lipoprotein profile or lipid profile) measures blood levels of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides.

  • Cholesterol The body uses cholesterol to help build cells and produce hormones. Too much cholesterol in the blood can build up along the inside of the artery walls, forming what is known as plaque. Large amounts of plaque increase your chances of having a heart attack or stroke.
  • HDL (high-density lipoprotein) cholesterol helps remove fat from the body by binding with it in the bloodstream and carrying it back to the liver for disposal. It is sometimes called “good” cholesterol. A high level of HDL cholesterol may lower your chances of developing heart disease or stroke.
  • LDL (low-density lipoprotein) cholesterol carries mostly fat and only a small amount of protein from the liver to other parts of the body. It is sometimes called "bad cholesterol." A high LDL cholesterol level may increase your chances of developing heart disease.
  • VLDL: (very low-density lipoprotein) cholesterol contains very little protein. The main purpose of VLDL is to distribute the triglyceride produced by your liver. A high VLDL cholesterol level can cause the buildup of cholesterol in your arteries and increases your risk of heart disease and stroke.
  • Triglycerides are a type of fat the body uses to store energy. Only small amounts are found in the blood. Having a high triglyceride level along with a high LDL cholesterol may increase your chances of having heart disease more than having only a high LDL cholesterol level.

 

Some medical experts recommend routine cholesterol and triglyceride testing to screen for problems that affect the way cholesterol is produced, used, carried in the blood, or disposed of by the body. Others may choose to routinely measure only total cholesterol and HDL levels.

  • National Cholesterol Education Panel (NCEP) guidelines for cholesterol screening
  • U.S. Preventive Services Task Force (USPSTF) guidelines for cholesterol screening
  • American College of Physicians (ACP) guidelines for cholesterol screening
  • American Heart Association guidelines for preventing coronary artery disease and stroke


Author:
Sydney Youngerman-Cole, RN, BSN, RNC
Last Updated October 6, 2005
Medical Review:
Caroline S. Rhoads, MD - Internal Medicine
Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology

 

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Blood Glucose


Test Overview

A blood glucose test measures the amount of a type of sugar, called glucose, in your blood. Glucose comes from carbohydrate foods. It is the main source of energy used by the body. Insulin is a hormone that helps your body use and control the amount of glucose in your blood. Insulin is produced in the pancreas and released into the blood when the amount of glucose in the blood rises.

Normally, your blood glucose levels increase slightly after you eat. This increase causes your pancreas to release insulin so that your blood glucose levels do not get too high. Blood glucose levels that remain high over time can damage your eyes, kidneys, nerves, and blood vessels.

Several different types of blood glucose tests are used.

  • Fasting blood sugar (FBS) measures blood glucose after you have not eaten for at least 8 hours. It often is the first test done to check for diabetes.
  • 2-hour postprandial blood sugar (2-hour PC) measures blood glucose exactly 2 hours after you eat a meal.
  • Random blood sugar (RBS) measures blood glucose regardless of when you last ate. Several random measurements may be taken throughout the day. Random testing is useful because glucose levels in healthy people do not vary widely throughout the day. Blood glucose levels that vary widely may indicate a problem. This test is also called a casual blood glucose test.
  • Oral glucose tolerance test is used to diagnose prediabetes and diabetes. An oral glucose tolerance test is a series of blood glucose measurements taken after you drink a sweet liquid that contains glucose. This test is commonly used to diagnose diabetes that occurs during pregnancy (gestational diabetes). For more information, see the medical test Gestational Diabetes. This test is not commonly used to diagnose diabetes in a person who is not pregnant.

 

Author:
Sydney Youngerman-Cole, RN, BSN, RNC
Last Updated August 26, 2005
Medical Review:
Caroline S. Rhoads, MD - Internal Medicine
David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism

 

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PROSTATE


Prostate-Specific Antigen (PSA)

Test Overview

A prostate-specific antigen (PSA) test measures the amount of prostate-specific antigen in the blood. PSA is released into a man's blood by his prostate gland. Healthy men have low amounts of PSA in the blood. The amount of PSA in the blood normally increases as a man's prostate enlarges with age. PSA may increase as a result of an injury, a digital rectal exam, sexual activity (ejaculation), inflammation of the prostate gland (prostatitis), or prostate cancer.

Prostate cancer often grows very slowly, without causing major problems. Detecting prostate cancer early and treating it may prevent some health problems and reduce the risk of dying from the cancer. However, some treatments for prostate cancer can cause other problems, such as controlling urination (incontinence) or erection problems (erectile dysfunction). Some men may choose not to have a PSA test or treat prostate cancer if it is detected. For example, a man older than age 75 who has no bothersome symptoms of prostate cancer may choose not to treat the cancer if it is found, so he would not need a PSA test.

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LIVER

Alanine Aminotransferase (ALT)

Test Overview

An alanine aminotransferase (ALT) test measures the amount of this enzyme in the blood. ALT is found mainly in the liver, but also in smaller amounts in the kidneys , heart , muscles, and pancreas . ALT formerly was called serum glutamic pyruvic transaminase (SGPT).
ALT is measured to see if the liver is damaged or diseased. Low levels of ALT are normally found in the blood. However, when the liver is damaged or diseased, it releases ALT into the bloodstream, which makes ALT levels go up. Most increases in ALT levels are caused by liver damage.

The ALT test is often done along with other tests that check for liver damage, including aspartate aminotransferase (AST), alkaline phosphatase, lactate dehydrogenase (LDH), and bilirubin. Both ALT and AST levels are reliable tests for liver damage.

Author:
Sydney Youngerman-Cole, RN, BSN, RNC
Last Updated January 18, 2006
Medical Review:
Martin Gabica, MD - Family Medicine
Jerome B. Simon, MD, FRCPC, FACP - Gastroenterology


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Aspartate Aminotransferase (AST)
Test Overview

An aspartate aminotransferase (AST) test measures the amount of this enzyme in the blood. AST is normally found in red blood cells, liver, heart, muscle tissue, pancreas, and kidneys. AST formerly was called serum glutamic oxaloacetic transaminase (SGOT).
Low levels of AST are normally found in the blood. When body tissue or an organ such as the heart or liver is diseased or damaged, additional AST is released into the bloodstream. The amount of AST in the blood is directly related to the extent of the tissue damage. After severe damage, AST levels rise in 6 to 10 hours and remain high for about 4 days.
The AST test may be done at the same time as a test for alanine aminotransferase, or ALT. The ratio of AST to ALT sometimes can help determine whether the liver or another organ has been damaged. Both ALT and AST levels can test for liver damage.

Author:
Sydney Youngerman-Cole, RN, BSN, RNC
Last Updated January 26, 2006
Medical Review:
Martin Gabica, MD - Family Medicine
Jerome B. Simon, MD, FRCPC, FACP - Gastroenterology

 

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PRO-TIME


Prothrombin Time

Test Overview

Prothrombin time (PT) is a blood test that measures how long it takes blood to clot. A prothrombin time test can be used to check for bleeding problems. PT is also used to check whether medicine to prevent blood clots is working.
About 12 blood clotting factors are needed for blood to clot (coagulation). Prothrombin, or factor II, is one of the clotting factors made by the liver. Vitamin K is needed to make prothrombin and other clotting factors. Prothrombin time is an important test because it checks to see if five different blood clotting factors (factors I, II, V, VII, and X) are present. The prothrombin time is made longer by:

  • Blood-thinning medicine, such as heparin. Another test, the activated partial thromboplastin time (APTT) test, is a better test to find out if the right dose of heparin is being used.
  • Low levels of blood clotting factors.
    A change in the activity of any of the clotting factors.
  • The absence of any of the clotting factors.
  • Other substances, called inhibitors, that affect the clotting factors.
  • An increase in the use of the clotting factors.
    An abnormal prothrombin time is often caused by liver disease or injury or by treatment with blood thinners.


Another blood clotting test, called partial thromboplastin time (PTT), measures other clotting factors. Partial thromboplastin time and prothrombin time are often done at the same time to check for bleeding problems or the chance for too much bleeding in surgery.

Author:
Jan Nissl, RN, BS
Last Updated September 25, 2006
Medical Review:
Patrice Burgess, MD - Family Medicine
Joseph O'Donnell, MD - Hematology

 

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