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 to clot.
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 medical conditions.
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 substances.
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 2 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 arteries.
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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