What is a screening test?
A screening test is done to detect potential health disorders or diseases in people who do not have any symptoms of disease. The goal is early detection and lifestyle changes or surveillance, to reduce the risk of disease, or to detect it early enough to treat it most effectively. Screening tests are not considered diagnostic, but are used to identify a subset of the population who should have additional testing to determine the presence or absence of disease.
When is a screening test helpful?
What makes a screening test valuable is its ability to detect potential problems, while minimizing unclear, ambiguous, or confusing results. While screening tests are not 100% accurate in all cases, it is generally more valuable to have the screening tests at the appropriate times, as recommended by your health care provider, than to not have them at all. However, some screening tests, when used in people not at high risk for disease, or when testing for very rare diseases, can cause more problems than they help.
Some common screening tests
Be sure to consult your health care provider regarding the appropriate timing and frequency of all screening tests based on your age, overall health, and medical history. The following are some examples of common screening tests:
Cholesterol measurements. Cholesterol is a waxy substance that can be found in all parts of the body. It aids in the production of cell membranes, some hormones, and vitamin D. The cholesterol in the blood comes from 2 sources: the food you eat and production in your liver. However, the liver produces all of the cholesterol the body needs.
Cholesterol and other fats are transported in the bloodstream in the form of spherical particles, called lipoproteins. The 2 most commonly known lipoproteins are low-density lipoproteins (LDL), or "bad" cholesterol, and high-density lipoproteins (HDL), or "good" cholesterol.
Cholesterol screening is performed by a blood test. People with high cholesterol measurements from a blood sample have a higher risk for cardiovascular disease (CVD), than those with cholesterol in the normal range. Studies have shown that people with high cholesterol can reduce their risk for heart disease by lowering their cholesterol. It is important to understand, however, that people can still have heart disease even with cholesterol levels in the normal range.
Fecal occult blood test. Fecal occult blood is detected by microscopic analysis or by chemical tests for hemoglobin (blood) in the stool. People with blood in their stool may have a cancerous growth indicative of colorectal cancer. The test requires collection of 3 stool samples that are examined under the microscope for blood. It is important to understand that when blood is present in a stool sample, it can be due to other noncancerous factors, such as certain medications or foods, gastrointestinal bleeding, or hemorrhoids. Testing is recommended starting at age 50 by many organizations including the American Cancer Society.
Pap test (also called Pap smears). Pap smears are samples of cells taken from the cervix in women to look for cellular changes indicative of cervical cancer. The Pap smear is an important screening test in sexually active women under the age of 65, to detect cancer at a stage when there are often no symptoms. It is important to understand that a Pap smear may be referred to as "abnormal," but may not mean that a person has cervical cancer. Some organizations also recommend HPV (human papilloma virus) screening in certain populations during the Pap smear.
Prostate specific antigen (PSA). This blood test measures the prostate specific antigen (PSA) levels in the blood. Antigens are any substances that evoke responses from a person's immune system. The prostate specific antigen levels can be elevated in the presence of prostate cancer. However, it is important to understand that other benign prostate conditions may also elevate PSA, such as benign prostatic hyperplasia (BPH), which is noncancerous swelling of the prostate. The PSA test is not recommended for all men, and there is considerable controversy over the role of PSA testing. Some organizations, such as the United States Preventive Services Task Force (USPSTF), now recommend against PSA screening. The pros and cons of PSA screening should always be discussed with your health care provider before testing. Some of the cons include unnecessary testing and procedures, unnecessary costs, and significantly increased anxiety.
Mammography. Many organizations, including the USPSTF, recommend mammography screening for breast cancer every 1 year to 2 years after age 50. This test is done in conjunction with a clinical breast exam.
Colonoscopy. Many organizations, including the USPSTF, recommend screening for colon cancer or colon polyps at age 50, earlier if you have a family history or other risk factors.
Consult your health care provider regarding all of these as well as other types of screening tests, based on your medical condition, as not all health care providers are in agreement in regard to which screening tests should be done and for which age groups.