Explanation of Laboratory Tests
The lipid profile is a group of tests that are often ordered together to determine risk of coronary heart disease. The tests that make up a lipid profile are tests that have been shown to be good indicators of whether someone is likely to have a heart attack or stroke caused by blockage of blood vessels (hardening of the arteries).
The lipid profile includes total cholesterol, HDL–cholesterol (often called good cholesterol), LDL–cholesterol (often called bad cholesterol), triglycerides, and Glucose. The lipid profile is used to guide providers in deciding how a person at risk should be treated. The results of the lipid profile are considered, along with other known risk factors of heart disease, to develop a plan of treatment and follow-up.
American Heart Association Guidelines
Less than 200 mg/dL Desirable (low risk)
200-239 mg/dL Borderline high (higher risk)
240 mg/dL and above (more than twice the risk as desirable level)
60 mg/dL and above = High HDL (lower risk)
40 to 59 mg/dL The higher, the better
Less than 40 mg/dL = Low HDL (higher risk)
Less than 100 mg/dL = Optimal for people with heart disease or diabetes
100 to 129 mg/dL = Near or above optimal
130 to 159 mg/dL = Bordline High
160 to 189 mg/dL = High
190 mg/dL and above = Very High
Less than 150 mg/dL = Normal
150 to 199 mg/dL = Bordeline High
200-499 mg/dL = High
500 mg/dL and above = Very High
Cholesterol is a substance (a steroid) that is essential for life. It forms the membranes for cells in all organs and tissues in your body. It is used to make hormones that are essential for development, growth, and reproduction. It forms bile acids that are needed to absorb nutrients from food.
A small amount of your body’s cholesterol circulates in the blood in complex particles called lipoproteins. These lipoproteins include some particles that carry excess cholesterol away for disposal (see HDL, good cholesterol) and some particles that deposit cholesterol in tissues and organs (see LDL, bad cholesterol). The test for cholesterol measures all cholesterol (good and bad) that is carried in the blood by lipoproteins.
High Density Lipoprotein (HDL)
HDL is one of the classes of lipoproteins that carry cholesterol in the blood. HDL is considered to be beneficial because it removes excess cholesterol and disposes of it. Therefore, HDL cholesterol is often termed “good” cholesterol. The test for HDL measures the amount of HDL cholesterol in blood.
Low Density Lipoprotein (LDL)
LDL is a type of lipoprotein that carries cholesterol in the blood. LDL is considered to be undesirable because it deposits excess cholesterol in walls of blood vessel and contributes to “hardening of the arteries” and heart disease. So LDL cholesterol is often termed “bad” cholesterol. The test for LDL measures the amount of LDL cholesterol in blood.
Blood tests for triglycerides are usually part of a lipid profile used to identify the risk of developing heart disease. If you are diabetic, it is especially important to have triglycerides measured as part of any lipid testing, since triglycerides increase significantly when blood sugar is out of control.
A normal level for fasting triglycerides is less than 150 mg/dL (1.70 mmol/L). It is unusual to have high triglycerides without also having high cholesterol. Most treatments for heart disease risk will be aimed at lowering cholesterol. However, the type of treatment used to lower cholesterol may differ depending on whether triglycerides are high or normal.
When triglycerides are very high (greater than 1000 mg/dL (11.30 mmol/L)), there is a risk of developing pancreatitis. Treatment to lower triglycerides should be started as soon as possible.
The glucose test is a snapshot, a still photograph, of a moving picture. It tells what the blood glucose level was at the moment it was collected. The fasting blood glucose level (collected after an eight to 12–hour fast) is used to screen for and diagnose diabetes and pre–diabetes.
High levels of glucose most frequently indicate diabetes, but many other diseases and conditions can also cause elevated glucose. The following information summarizes the meaning of the test results. These are based on the clinical practice recommendations of the American Diabetes Association.
Fasting Blood Glucose
From 70 to 110 mg/dL (3.9 to 6.0 mmol/L)
normal glucose tolerance
From 111 to 125 mg/dL (6.1 to 6.9 mmol/L)
impaired fasting glucose (pre-diabetes)
126 mg/dL (7.0 mmol/L) and above
Thyroid Stimulating Hormone (TSH)
Your doctor orders this test if you show symptoms of a thyroid disorder. For example, symptoms of hyperthyroidism include heat intolerance, weight loss, rapid heartbeat, nervousness, insomnia, and breathlessness. Common symptoms of hypothyroidism include fatigue, weakness, weight gain, slow heart rate, and cold intolerance.
A high TSH result often means an underactive thyroid gland caused by failure of the gland (hypothyroidism). Rarely, a high TSH result can indicate a problem with the pituitary gland, such as a tumor producing unregulated levels of TSH, in what is known as secondary hyperthyroidism. A high TSH value can also occur in people with underactive thyroid glands who have been receiving too little thyroid hormone medication.
A low TSH result can indicate an overactive thyroid gland (hyperthyroidism). A low TSH result can also indicate damage to the pituitary gland that prevents it from producing TSH. A low TSH result can also occur in people with an underactive thyroid gland who are receiving too much thyroid hormone medication.
Prostate Specific Antigen (PSA)
The American Cancer Society recommends annual PSA and digital rectal exams for all men beginning at age 50. Men who have an increased risk for prostate cancer (such as men of African descent and men with a family history of the disease) should start getting tested earlier, usually at age 40 or 45.
PSA screening is somewhat controversial, however, because in many cases PSA testing of healthy men may be detecting early cancers that are extremely slow–growing and may never cause life–threatening disease. This may cause further unnecessary testing and treatment.
The normal value for total PSA is under 4.0 nanograms per milliliter of blood. Total PSA levels greater than 10.0 ng/ml may indicate a high probability of prostate cancer. Levels between 4.0 ng/ml and 10.0 ng/ml may indicate BPH, a non–cancerous swelling of the prostate. This occurs most frequently in elderly men. Increased total PSA levels may also indicate a condition called prostatitis, which is caused by an infection.