How to review your blood test results

Overview

Laboratory tests are tools helpful in evaluating the health status of an individual. It is important to realize that laboratory results may be outside of the so-called "normal range" for many reasons. These variations may be due to such things as race, dietetic preference, age, sex, menstrual cycle, degree of physical activity, problems with collection and/or handling of the specimen, non-prescription drugs (aspirin, cold medications, vitamins, etc.), prescription drugs, alcohol intake and a number of non-illness-related factors, Any unusual or abnormal results should be discussed with your physician. It is not possible to diagnose or treat any disease or problem with this blood test alone. It can, however, help you to learn more about your body and detect potential problems in early stages when treatment or changes in personal habits can be most effective. .

This review is a brief summary and is not intended to be comprehensive or replace discussion of your results with your health care team.

Glucose: This is a measure of the sugar level in your blood. High values are associated with eating before the test, and diabetes.

The normal range for a fasting glucose is 60 -109 mg/dl. According the the 1999 ADA criteria, diabetes is diagnosed with a *fasting* plasma glucose of 126 or more. A precursor, Impaired Fasting Glucose (IFG) is defined as reading of fasting glucose levels of 110 - 125. Sometimes a glucose tolerance test, which involves giving you a sugary drink followed by several blood glucose tests, is necessary to properly sort out normal from IFG from diabetes.

Be aware that variations in lab normals exist. Also, Europeans tend to use a 2 hour after eating definition of diabetes rather than a fasting glucose. Using the European standards tends to increase the number of people who are classified as having diabetes.

Electrolytes: These are your potassium, sodium, chloride, and CO2 levels.

Potassium is 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. This is especially important if you are taking a diuretic (water pill) or heart pill (Digitalis, Lanoxin, etc.).

Sodium is also regulated by the kidneys and adrenal glands. There are numerous causes of high and low sodium levels, but the most common causes of low sodium are diuretic usage, diabetes drugs like chlorpropamide, and excessive water intake in patients with heart or liver disease.

CO2 reflects the acid status of your blood. Low CO2 levels can be due to either to increased acidity from uncontrolled diabetes, kidney disease, metabolic disorders, or low CO2 can be due to chronic hyperventilation.

Waste products:

Blood Urea Nitrogen (BUN) is a waste product produced in the liver and excreted by the kidneys. High values may mean that the kidneys are not working as well as they should. BUN is also affected by high protein diets and/or strenuous exercise which raise levels, and by pregnancy which lowers it.

Creatinine is a waste product largely from muscle breakdown. High values, especially with high BUN levels, may indicate problems with the kidneys..

Uric Acid is normally excreted in urine. High values are associated with gout, arthritis, kidney problems and the use of some diuretics.

Enzymes

AST, ALT, SGOT, SGPT, and GGT and Alkaline Phosphatase are abbreviations for proteins called enzymes which help all the chemical activities within cells to take place. Injury to cells release these enzymes into the blood. They are found in muscles, the liver and heart. Damage from alcohol and a number of diseases are reflected in high values.

Alkaline phosphatase is an enzyme found primarily in bones and the liver. Expected values are higher for those who are growing (children and pregnant women) or when damage to bones or liver has occurred or with gallstones. Low values are probably not significant.

GGT is also elevated in liver disease, particularly with obstruction of bile ducts. Unlike the alkaline phosphatase it is not elevated with bone growth or damage.

AST/SGOT , ALT/ SGPT are also liver and muscle enzymes. They may be elevated from liver problems, hepatitis, excess alcohol ingestion, muscle injury and recent heart attack.

LDH is the enzyme present in all the cells in the body. Anything which damages cells, including blood drawing itself, will raise amounts in the blood. If blood is not processed promptly and properly, high levels may occur. If all values except LDH are within expected ranges, it is probably a processing error and does not require further evaluation.

Bilirubin: is a pigment removed from the blood by the liver. Low values are of no concern. If slightly elevated above the expected ranges, but with all other enzymes (LDH, GOT, GPT, GGT) within expected values, it is probably a condition known as Gilbert’s syndrome and is not significant

CPK is an enzyme which is very useful for diagnosing diseases of the heart and skeletal muscle. This enzyme is the first to be elevated after a heart attack (3 to 4 hours). 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 type of protein in your blood. They are a general index of overall health and nutrition. Globulin is the "antibody" protein important for fighting disease.

A/G Ratio is the mathematical relationship between the above.

Blood Fats

Cholesterol is a fat-like substance in the blood which, if elevated has been associated with heart disease. Less than 200 is recommended by the National Heart, Lung, and Blood Institute.

Total Cholesterol: A high cholesterol in the blood 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. However, when the level gets too high, serious problems can result. Levels of 200 or more are too high for good health. Levels of 240 and above are considered high risk, and may indicate the need for cholesterol lowering medication. A low fat diet and regular exercise are recommended. As the level of blood cholesterol increases, so does the possibility of plugging the arteries due to cholesterol plaque build-up. Such a disease process is called "hardening of the arteries" or atherosclerosis. When the arteries feeding the heart become plugged, a heart attack may occur. If the arteries that go to the brain are affected, then the result is a stroke.

There are three major kinds of cholesterol, High Density Lipoprotein (HDL) , Low Density Lipoprotein (LDL), and Very Low Density Lipoprotein (VLDL).

LDL Cholesterol is considered "bad cholesterol" because cholesterol deposits form in the arteries when LDL levels are high. An LDL level of less than 130 is recommended, 100 is ideal, values greater than 160 are considered high risk and should be followed up by your physician. Those persons who have established coronary or vascular disease may be instructed by their doctor to get their LDL Cholesterol well below 100. You should ask your doctor which LDL target he or she wants for you.

HDL cholesterol is a ‘good cholesterol’ as 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.

Triglyceride is fat in the blood which, if elevated, has been associated with heart disease, especially if over 500 mg. High triglycerides are also associated with pancreatitis. Triglyceride levels over 150 mg/dl may be associated with problems other than heart disease. Ways to lower triglycerides: 1) weight reduction, if overweight; 2) reduce animal fats in the diet: eat more fish; 3) take certain medications your physician can prescribe; 4) get regular aerobic exercise; 5) decrease alcohol and sugar consumption—alcohol and sugar are not fats, but the body can convert them into fats then dump those fats into your blood stream.

VLDL (very low density lipoprotein) is another carrier of fat in the blood.

Minerals

Calcium is 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. An elevated calcium can be due to medications such as thiazide type diuretics, inherited disorders of calcium handling in the kidneys, or excess parathyroid gland activity or vitamin D. Low calcium can be due to certain metabolic disorders such as insufficient parathyroid hormone; or drugs like Fosamax or furosemide type diuretics.

Phosphorus is also largely stored in the 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 suggests parathyroid disease, however there are other causes. A low phosphorus, in combination with a high calcium, may suggest an overactive parathyroid gland.

Thyroid

There are 2 types of thyroid hormones easily measurable in the blood, thyroxine (T4) and triiodothyronine (T3). For technical reasons, it is easier and less expensive to measure the T4 level, so T3 is usually not measured on screening tests.

Please be clear on which test you are looking at. We continue to see a tremendous amount of confusion among doctors, nurses, lab techs, and patients on which test is which. In particular, the "Total T3", "Free T3" and "T3 Uptake tests" are very confusing, and are not the same test.

Thyroxine (T4) . This shows the total amount of the T4. High levels may be due to hyperthyroidism, however technical artifact occurs when estrogen levels are higher from pregnancy, birth control pills or estrogen replacement therapy. A Free T4 (see below) can avoid this interference.

T3 Resin Uptake or Thyroid Uptake. This is a test that confuses doctors, nurses, and patients. First, this is not a thyroid test, but a test on the proteins that carry thyroid around in your blood stream. Not only that, a high test number may indicate a low level of the protein! The method of reporting varies from lab to lab. The proper use of the test is to compute the free thyroxine index.

Free Thyroxine Index (FTI or T7) : A mathematical computation allows the lab to estimate the free thyroxine index from the T4 and T3 Uptake tests. The results tell us how much thyroid hormone is free in the blood stream to work on the body. Unlike the T4 alone, it is not affected by estrogen levels.

Free T4 : This test directly measures the free T4 in the blood rather than estimating it like the FTI. It is a more reliable , but a little more expensive test. Some labs now do the Free T4 routinely rather than the Total T4.

Total T3: This is usually not ordered as a screening test, but rather when thyroid disease is being evaluated. T3 is the more potent and shorter lived version of thyroid hormone. Some people with high thyroid levels secrete more T3 than T4. In these (overactive) hyperthyroid cases the T4 can be normal, the T3 high, and the TSH low. The Total T3 reports the total amount of T3 in the bloodstream, including T3 bound to carrier proteins plus freely circulating T3.

Free T3: This test measures only the portion of thyroid hormone T3 that is "free", that is, not bound to carrier proteins.

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, and 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 3 months, it tells us your average glucose for the last 6 - 8 weeks. A high level suggests poor diabetes control. Standardization for glycohemoglobin from lab to lab is poor, and you cannot compare a test from different labs unless you can verify the technique for measuring glycohemoglobin is the same. The only exception is if your lab is standardized to the national DCCT referenced method. You can ask your lab if they use a DCCT referenced method.

Copyright 1997-2003 Amarillo Medical Specialists, LLP , used with permission

http://www.amarillomed.com/howto.htm