There are three main categories of cells in human blood: red blood cells
(RBCs), white blood cells (WBCs) and platelets. Red blood cells
carry oxygen to the body tissues. Hemoglobin is a protein in the red
blood cells that is responsible for oxygen "transportation." White blood
cells play a vital role in immunity—the body's ability to fight off
illness. There are several different types of white blood cells, each
having different functions related to immunity. Platelets help the blood
A complete blood count, or CBC, is a count of the red blood cells, white
blood cells and platelets in a definite volume of blood. A CBC also
includes a measurement of hemoglobin, the protein that carries oxygen
within the red blood cells. A hematocrit is a measurement of the percent
volume of red cells, white cells and plasma. A differential WBC count is
a count of the different types of white blood cells.
A CBC can tell your doctor a great deal about the state of your health.
Medical conditions that cause an abnormal blood count include anemia,
the presence of an infection and some kinds of cancer. Blood counts can
be used for screening, diagnosis or management of certain diseases and
Synonyms: Routine urinalysis, UA
Routine urinalysis includes the examination of the physical and chemical
characteristics of urine. A routine urinalysis may also include a
microscopic examination, if needed. Physical and chemical
characteristics include color, appearance, specific gravity (a measure
of dissolved substances), pH (acidity), the presence of protein, glucose
(sugar), occult ("hidden") blood and other chemicals. The microscopic
examination may find casts, crystals, blood and other types of cells.
A routine urinalysis can tell your doctor a great deal. Diabetes,
urinary tract infections and kidney problems are among the many medical
conditions that can be detected by routine urinalysis results. Very
often, a routine urinalysis is part of a general physical exam.
A routine urinalysis does not detect drugs of abuse. A special
drugs-of-abuse screening test is used to detect the presence of those
The Pap, short for Papanicolau test, is very valuable for the early
detection of cancer of the cervix and uterus. The cervix is the opening
connecting the uterus and vagina. The doctor takes a sample of the cells
from the cervix and puts them on a slide or in a liquid. The cells are
stained and carefully examined under a microscope.
Patients should prepare in the following manner before visiting the
doctor for a Pap smear:
Schedule your visit for approximately two weeks after the first
day of the last menstrual period.
Stop using vaginal medications 72 hours before the exam.
Abstain from sexual relations 24 hours before the exam.
The Pap is a screening test, which means that a "negative" Pap smear is
good—it means the patient is at lower risk for cervical cancer. A
"positive" or "abnormal" result indicates that the patient is possibly
at higher risk for cervical cancer, and additional tests are required
for a diagnosis.
If the Pap smear shows an abnormality, a follow-up Pap may be done in 3
to 6 months. In most cases, the abnormality is due to inflammation or
infection. If the second Pap is abnormal, the doctor may order a
colposcopy. A colposcopy is a procedure in which the doctor takes a
closer look at the cervix using a magnifying lens. The doctor may want
to take a biopsy (a specimen of tissue) for microscopic examination to
determine if precancerous cells are present. Cervical cancer develops
very slowly, so early diagnosis means a much better chance of successful
treatment. Since the 1940s, when Pap smears were first introduced, the
incidence of cervical cancer has decreased by 70 percent.
The American College of Obstetricians and Gynecologists recommends a
yearly Pap smear for women who are over the age of 18 or sexually
active. If three consecutive Pap smears are negative, screenings may be
done every two or three years.
An occult or "hidden" blood test is a screening test for colorectal
cancer, the second leading cause of cancer death in the U.S. The word colorectal
refers to the colon, or large intestine, and the rectum, the end of the
digestive system. The specimen is a small sample of feces that is
smeared onto a card and can be taken in the doctor's office or at home.
The specimen on the card is then chemically tested for the presence of
blood. Certain foods and medications, such as aspirin and ibuprofen,
should be avoided before taking an occult blood test.
A positive fecal occult blood result may indicate bleeding in the colon
or rectum and shows increased risk of colorectal cancer. Other tests
also used for colorectal cancer screening are barium enema, colonoscopy,
sigmoidoscopy and digital rectal examination.
The incidence of colorectal cancer in men and women is about equal.
People over the age of 50, those who have a family history and those who
have previously had colorectal cancer are at higher risk of developing
the disease. Most doctors recommend fecal occult blood screening every
year for everyone over 50. Early detection of colorectal cancer greatly
improves the odds of successful treatment.
Cholesterol is a white, waxy substance that is found naturally in the
body. It is produced by the liver to build cell walls and make certain
hormones. You can't function without a certain amount of cholesterol,
but the body makes all that it needs. And yet, because of the animal
products we eat, many of us have an unhealthy surplus of cholesterol.
Too much cholesterol in the blood is a major cause of heart disease and
blood vessel disease. Cholesterol forms plaques that clog the arteries
and eventually choke off the supply of blood to the heart (causing heart
attacks) and to the brain (leading to stroke). By lowering your
cholesterol level you may be able to stop plaques from developing in the
arteries and shrink plaques that have already formed.
If you have already had a heart attack or bypass surgery, your
healthcare provider should check your cholesterol level regularly.
Keeping the level low is one of the best insurances against blocked
Your cholesterol level can be broken down into two parts:
The high-density lipoprotein (HDL) cholesterol, which is
referred to as the "good" cholesterol because of its ability to
take cholesterol and remove it from the arteries.
The low-density lipoprotein (LDL) cholesterol, or the "bad"
cholesterol, which builds up and clogs the arteries.
An HDL cholesterol reading above 60 is very good. The higher the HDL
cholesterol number, the lower your chance of having a heart attack or
stroke. Your LDL cholesterol reading should be lower than 130—and the
lower, the better.
If you do not know your cholesterol readings, call your healthcare
provider for testing. The cholesterol test is best done after a 12-hour
fast and by a laboratory that measures HDL, LDL and other blood
components. Cholesterol screenings that are sometimes done at health
fairs and shopping centers are only somewhat helpful, because they do
not usually measure HDL and LDL cholesterol separately.
A triglyceride level is also an important component of cholesterol
testing. The triglyceride level reflects the amount of fat in the blood
at the time the test is taken. A triglyceride level of less than 200 (in
a fasting patient) is considered good. Cholesterol (HDL and LDL) and
triglyceride results are most meaningful when the patient has been
fasting overnight (had no food or drinks with calories).
Most of the food we eat is turned into glucose, a type of sugar. Shortly
after we eat, the pancreas, a small organ located beneath the stomach,
produces a hormone called insulin. Insulin helps the body tissues absorb
glucose from the blood. If our body does not make enough insulin, or the
body does not use insulin well, glucose begins to build up in the blood.
This condition is called diabetes.
Testing blood glucose levels is the first and most common test for the
diagnosis and management of diabetes. Blood glucose levels are most
useful when the patient has been fasting (has had nothing to eat) for 12
or more hours.
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