| Interpretation
of Lab Results
Did you ever wonder what your doctor is checking for when he or she
does your blood work? Most people know about cholesterol, but how about
the BUN? I will attempt to explain the meaning of the blood work results.
The glucose (blood sugar) is a test for diabetes. Normal values are
below 100. Diabetes is defined as a fasting blood sugar of greater than
126 on two separate occasions. Frequently it will be on the low side,
but this is rarely of any significance. The value for the blood sugar
will decrease if the test is not performed shortly after it is drawn.
If it is very low, you may want to go by your doctor's office and get
a finger stick for the blood sugar level, so that it can be analyzed
immediately.
Sodium, chloride, potassium, and magnesium are called electrolytes,
and they will sometimes become significantly abnormal with certain medications
or different forms of lung, heart, or kidney disease. They are not related
to the amount of salt you have in your diet. Water pills are most frequently
implicated when the potassium is low. Some antidepressants and water
pills can cause the sodium and chloride to be low.
Calcium and phosphorus are minerals in your bones, and they may be abnormal
with certain hormonal diseases, or may be related to tumors in your
bones. Phosphorous is difficult to test and is frequently out of the
normal range. It is rarely a significant abnormality, but your physician
can decide whether or not to pursue a mildly abnormal result.
The protein, albumin, A/G ratio and globulin results of your blood work
are a measure of the liver function and will be abnormal with liver
damage as seen in cirrhosis of the liver. The alkaline phosphatase,
lactate dehydrogenase, gamma-glutamyl transferase, SGOT, and SGPT results
are a measure of on going liver damage. Liver damage could be seen as
a reaction to numerous medications, alcohol toxicity, hepatitis, tumors
in the liver, or a number of viral illnesses. Frequently, one or two
of these tests may be only slightly elevated which is not always significant,
but may have to be repeated at a later date, after stopping medicines
or avoiding alcoholic beverages.
The BUN, creatinine, and BUN/creatinine ratio are a very accurate measure
of kidney function. The creatinine will be elevated with significant
renal disease. A low serum creatinine or BUN is not usually a sign of
disease.
Uric acid is a chemical in the body that may cause gout if it becomes
elevated. Gout is a hereditary form of arthritis. A low uric acid is
rarely a sign of disease.
Iron, iron binding capacity, and % saturation measure the amount of
iron you have in your body. Results may be low because of poor dietary
intake of iron, or from loss of blood from the body. A low serum iron
is frequently seen in women that have heavy periods and have a diet
low in iron. Bleeding from the gastrointestinal tract can also result
in a low serum iron. This bleeding may be visible blood loss, or it
may be occult, which means it is not readily apparent to the naked eye.
It is important to check for blood in the stool if you iron is low.
Occult blood in the stool can be tested with Hemocult slides (stool
cards).
The desired level of total cholesterol is under 200. It is important
to measure the HDL-cholesterol and the LDL-cholesterol. The HDL- cholesterol
is the good cholesterol, and it is okay for it to be high. It seems
to protect the heart and blood vessels from becoming clogged. One way
to estimate your risk of having heart disease, is to divide the total
cholesterol by the HDL-cholesterol. This ratio, ideally, should be less
than 3.5, which would be associated with only one-half the risk of an
average person having a heart attack. Your ratio can be improved by
increasing the HDL-cholesterol, or decreasing the total cholesterol.
This can usually be accomplished by regular aerobic exercise, such as
walking, running, swimming, aerobic classes, or any exercise that maintains
your heart rate at a fairly high level. You should attempt to maintain
your heart rate at 70% or greater of your maximal predicted heart rate.
Your predicted maximal heart rate is estimated by subtracting your age
from 220. If you are 40 years old, your predicted maximal heart rate
is 220-40=180. Therefore, 70% of this would be 126. You should try to
SLOWLY get to the point where you can exercise for 30-60 minutes a day,
keeping your heart rate above 125 beats per minute. Ideally, this should
be done daily.
Your cholesterol level is determined by heredity, exercise, and diet.
Unfortunately, heredity can be a very powerful influence on both the
total cholesterol, LDL-cholesterol and the HDL-cholesterol level. Diet
alone has minimal effect on cholesterol. Exercise has some effect particularly
on increasing the HDL and lowering the total cholesterol and LDL-cholesterol.
Diet and exercise together are the best non-medicinal treatment. Medications
called statins have been a major advance in the treatment of high cholesterol.
The LDL-cholesterol is used to decide whether or not someone should
take a statin. It should be less than 130 in healthy individuals and
less than 70 in individuals with diabetes or heart disease. Examples
of statins are Mevacor, Lipitor, Pravochol and Crestor. Mevacor is presently
the only generic statin. It works very well and is usually well tolerated.
It is important to realize that the cholesterol level may vary somewhat
from day to day, and if you have an abnormal reading, it may need to
be checked on several occasions to really get a good feel for its true
value.
Triglycerides are another fat in your blood that are not quite as important
as the cholesterol in the development of heart disease. The amount of
this fat in your blood is influenced by your diet, and if it is elevated,
you may need to get the test repeated when you are fasting. Eating within
14 hours of the blood test, may make the triglycerides go up.
The complete blood count (CBC) checks your white blood cells (WBCs)
as well as your red blood cells. The red blood cells, hemoglobin, hematocrit,
mcv, mch, mchc and rdw all are checks for different kinds of anemia.
Anemia is when your hemoglobin level is low, and you may manifest symptoms
such as fatigue, headaches, and weakness.
Your WBCs are responsible for fighting off infection. They may decrease
if you have certain viral infections, but they increase with most bacterial
infections.
Platelets are involved in making your blood clot; occasionally, they
will decrease to very low levels with certain viral infections. The
Neutrophils, lymphocytes, monocytes, eosinophils, and basophils are
specific types of WBCs, that are counted by hand as well as by the machine
performing CBCs. The percentages of different types of WBCs will vary
with many factors, such as viral infections, age, and even recent exercise.
If you have allergies, the eosinophil count will frequently be elevated.
The TSH (thyroid stimulating hormone) is a hormone that is a very sensitive
measure of your thyroid function. The thyroid gland is in the neck and
produces a hormone called thyroxine, that is responsible for your metabolism.
An under active thyroid will cause fatigue, constipation and depression,
along with numerous other symptoms. An overactive thyroid will cause
anxiety, weight loss, diarrhea, and many other symptoms. The TSH level
is inversely related to your thyroid gland output of hormone. The brain
monitors the thyroid hormone in the blood, and sends out more TSH when
the thyroid hormone level gets low, stimulating the thyroid gland to
produce more thyroid hormone. However, if the thyroid hormone level
is high in the blood, the brain senses this and decreases the production
of TSH. This is a signal for the thyroid gland to decrease the production
of thyroid hormone.
The PSA stands for prostate specific antigen that is a screening test
for cancer of the prostate gland. The American Cancer Society recommends
that men over the age of 50 have a yearly PSA test. Men over the age
of 40 should have a yearly PSA if they have a family history of prostate
cancer, or if they are African-American.
FSH (follicle stimulating hormone) is a hormone secreted by a part
of the brain known as the pituitary gland. It is frequently ordered
in females to see if they are going through menopause. It will become
elevated when menopause begins.
Many people will have one or more of the test results in the abnormal
column. This is usually not significant, but should be discussed with
the doctor.
The urinalysis is a test for evidence of a urinary tract infection,
diabetes, kidney disease, or liver disease.
Other tests that may or may not have been performed, depending on your
age and sex, are the EKG and PAP smear. The PAP smear will check for
cancer of the cervix. The EKG will check for evidence of heart disease.
If you were given Hemocult slides, be sure to complete them and send
them back to the lab to check for cancer of the colon. It has been proven
that you will reduce your chance of dying of colon cancer by 30% if
you perform this simple test every year. Just try to do the best you
can with the dietary restrictions. The only factor that is particularly
important is to adhere to the recommendation of not taking over 250
mg of vitamin C for three days before completing the test.
The information provided above is offered as a community service about
health-care issues and is not a substitute for individual consultation.
Advice on individual problems should be obtained from your personal
physician. This information is based on research by the author and represents
his interpretation of the literature.
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Readers may send questions to our
email address. This column is for informational purposes only and
is not a substitute for professional or medical advice.
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