Good Health Newsletter

Fall 2006

Studying up on Clinical Lab Tests Helps
to Educate You as a Health Care Consumer

There's no question that clinical laboratory tests play a crucial role in medical decision-making. And as the U.S. health care system has evolved, patients and their families have had to take a more active role in the care that they receive.

That's why it's more important than ever to take responsibility for understanding your care and the information on which critical decisions are based - including lab tests.

This issue of Steps to Good Health provides you with a valuable overview of lab tests and what they can reveal, so you can communicate with your doctor as an informed health care consumer.

Properly preparing for lab test an important step

Like many areas of medicine, clinical lab tests often provide a few simple answers to commonly asked questions about the state of your health.

Taken in context with the rest of the information available to your doctor, however, they provide a significant piece of the puzzle.

Test results are usually interpreted based on their relation to a reference range of "normal" values. If your results are out of the "normal range," it may be a signal that further investigation is needed.

One of your first responsibilities in the testing process should be to inform your doctor if you have had other recent lab tests ordered by another physician. If that's the case, he or she should be able to get copies of these results - perhaps eliminating the need for additional testing.

Here are some other tips to make sure you are well prepared:

Follow instructions, if there are any, to prepare for the specific test you are having performed. For example, you may be asked to refrain from eating or drinking anything for a specific period of time before your test.
Alert the person collecting your sample if you have deviated from the instructions and how.
Inform your health care provider of any medications you are taking, including prescription drugs, over-the-counter drugs or herbal remedies.

Lab Tests 101 Here's a brief summary of some of the most commonly ordered lab tests. (This is not intended to be a comprehensive list or to replace discussion of your results with your physician.)
Glucose: This is a measure of the sugar level in your blood. High values are associated with diabetes, but may also be triggered by eating before the test. Electrolytes Potassium: An element controlled very carefully by the kidneys, it is important for the proper functioning of the nerves and muscles, particularly the heart. Any value outside the expected range, high or low, requires medical evaluation. Sodium: Element also regulated by the kidneys and adrenal glands. There are numerous causes of high and low sodium levels. Carbon dioxide (CO2): CO2 levels reflect the acid status of your blood. Low CO2 levels can be due to increased acidity from uncontrolled diabetes, kidney disease, metabolic disorders or chronic hyperventilation. Waste products Blood Urea Nitrogen (BUN): A waste product produced in the liver and excreted by the kidneys. High values may mean the kidneys are not working as well as they should. Creatinine: A waste product largely from muscle breakdown. High values, especially in conjunction high BUN levels, may indicate problems with the kidneys. Uric Acid: Normally excreted in urine. High values are associated with gout, arthritis, kidney problems and the use of some diuretics. Enzymes Proteins called enzymes help enable all the chemical activities that take place within cells. Injury to cells releases these enzymes into the blood. They are found in muscles, the liver and the heart. Damage from alcohol and a number of diseases are reflected in high values. There are several types of enzymes: Alkaline phosphatase: An enzyme found primarily in bones and the liver. Expected values are higher for those who are growing - such as children and pregnant women - or when damage to bones or liver has occurred, or with gallstones. Low values are typically not significant. GGT: This enzyme is also elevated in liver disease, particularly with obstruction of the bile ducts. AST/SGOT and ALT/SGPT: More liver and muscle enzymes. They may be elevated from liver problems, hepatitis, excess alcohol ingestion, muscle injury or a recent heart attack. LDH: An enzyme present in all the cells in the body. Anything that damages cells, including the drawing of blood itself, will raise amounts in the blood. Bilirubin: A pigment removed from the blood by the liver. Low values are of no concern, but high levels can be. CPK: An enzyme that is very useful for diagnosing diseases of the heart and skeletal muscles. It is the first to be elevated following a heart attack - within three to four hours after the attack. If CPK is high in the absence of heart muscle injury, this is a strong indication of skeletal muscle disease. Proteins Albumin and Globulin: Measure the amount and types of protein in your blood. They are a general index of overall health and nutrition. Globulin is the "antibody" protein important for fighting disease.		Blood Fats Cholesterol is a fat-like substance in the blood, which - if elevated - has been associated with heart disease. Total cholesterol: High total cholesterol is a major risk factor for heart and blood vessel disease. Cholesterol in itself is not all bad. In fact, our bodies need a certain amount of this substance to function properly. When the level gets too high, however, vascular disease can result. Total cholesterol of less than 200 and a Low Density Lipoprotein (LDL) cholesterol level of 100 or less are considered optimal by the National Heart, Lung and Blood Institute. As the level of blood cholesterol increases, so does the possibility of your arteries becoming plugged due to cholesterol plaque build-up. This is called atherosclerosis or "hardening of the arteries." When the arteries feeding the heart become plugged, a heart attack may occur. If the arteries that go to the brain are affected, the result is a stroke. In addition to the LDL cholesterol mentioned above, there are two other major kinds of cholesterol. They are High Density Lipoprotein (HDL) and Very Low Density Lipoprotein (VLDL). LDL cholesterol: Considered "bad cholesterol" because cholesterol deposits form in the arteries when LDL levels are high. HDL cholesterol: Known as "good cholesterol," it protects against heart disease by helping remove excess cholesterol deposited in the arteries. High levels seem to be associated with low incidence of coronary heart disease. Triglycerides: A fat in the blood that, when elevated, has been associated with heart disease - especially if over 500 milligrams. VLDL cholesterol: Another carrier of fat in the blood. Cardiac Risk Factors C Reactive Protein (CRP): This is a general marker for inflammation. Traditionally, it has been used to assess inflammation in response to infection. It may be especially significant when evaluating risk for vascular disease, heart attack or stroke. Homocysteine: This is an amino acid normally found in small amounts in the blood. Higher levels are associated with increased risk of heart attack and other vascular diseases. Homocysteine levels may be high due to a deficiency of folic acid or vitamin B-12 or due to heredity, older age, kidney disease and certain medications. Lipoprotein(a) [Lp(a)]: Elevated Lp(a) concentrations are associated with premature coronary heart disease. The exact mechanism is not yet clear, but it appears that there is a strong genetic component to elevated Lp(a) levels that correlates with coronary disease. Minerals Calcium: Controlled in the blood by the parathyroid glands and the kidneys. Calcium is found mostly in bone and is important for proper blood clotting, nerve and cell activity. Phosphorus: A mineral largely stored in bone. It is regulated by the kidneys, and high levels may be due to kidney disease. When low levels are seen with high calcium levels, it may suggest parathyroid disease.		Thyroid Thyroxine (T4) and triiodothyronine (T3): The two types of thyroid hormones easily measurable in the blood. Thyroid Stimulating Hormone (TSH): This protein hormone is secreted by the pituitary gland and regulates the thyroid gland. A high level suggests your thyroid is underactive, while a low level suggests your thyroid is overactive. Glycohemoglobin [Hemoglobin A1 or A1c (HbA1c)]: Glycohemoglobin measures the amount of glucose chemically attached to your red blood cells. Since blood cells live about three months, it tells us your average glucose for the last six to eight weeks. A high level suggests poor diabetes control. Hormones Insulin: Secreted by the pancreas in response to eating or elevated blood sugar. It is deficient in people with type 1 diabetes and present at insufficient levels in people with type 2 diabetes. Estradiol: This is the most commonly measured type of estrogen. In women, it varies according to their age and whether they are having normal menstrual cycles. Levels of this hormone also change when taking birth control pills or estrogen replacement. Complete Blood Count (CBC) CBC typically has several values created from an automated cell counter. These are the most relevant: White Blood Count (WBC): The number of white cells. High WBC can be a sign of infection. Hemoglobin (Hgb) and Hematocrit (Hct): Hemoglobin is the amount of oxygen-carrying protein contained within the red blood cells. The hematocrit is the percentage of the blood volume occupied by red blood cells. Mean Corpuscular Volume (MCV): Helps diagnose a specific cause of an anemia. Platelet Count (PLT): The number of cells that may plug up holes in your blood vessels and prevent bleeding. High values can occur with bleeding, cigarette smoking or excess production by the bone marrow. Low values can occur from premature destruction states, acute blood loss, the effects of drugs such as heparin, infections, entrapment of platelets in an enlarged spleen, or bone marrow failure. Urinalysis Urine tests are typically evaluated with a reagent strip that is briefly dipped into your urine sample. The technician reads the colors of each test and compares them with a reference chart. pH: This is a measure of acidity for your urine. Specific Gravity (SG): This measures how dilute your urine is. It can vary greatly depending on when you drank fluids last or if you are dehydrated. Glucose: Normally, there is no glucose in urine, but a positive glucose reading occurs in people with diabetes. There are a small number of people that have glucose in their urine with normal blood glucose levels. Protein: There normally is no protein detectable on a urinalysis strip. If detected, protein can indicate kidney damage, blood in the urine or an infection. Blood: There normally is no blood in the urine. Blood can indicate an infection, kidney stones, trauma, or bleeding from a bladder or kidney tumor Bilirubin: Pigments that are cleared by the liver, bilirubin or urobilinoge aren't normally found in urine, except in cases of liver or gallbladder disease.

The information contained in this newsletter is not intended to replace the advice of your healthcare provider. If you have any questions about managing your health and/or seeking medical care, please contact a medical professional.