FAQ's
Understanding Blood Tests During Chemotherapy
From:The Chemotherapy Survival Guide By:Judith McKay, R.N., Nancee Hirano, R.N., M.S.N.
When you are ill, it seems that everyone is after your blood. Every time you look up there’s someone in a lab coat, carrying a tourniquet and multicolored test tubes, who needs just a few more ounces. You wonder why so many tests? Why so often? You may even feel that you are giving too much blood and worry how and when your body will replace it.
You have about four to five quarts of blood in your body, and most blood tests require only about a teaspoon of blood in each test tube. The few teaspoons of blood you lose each time blood is drawn for a test are rapidly replaced. Even someone donating a pint of blood replaces it so quickly that he or she can donate again in about two weeks.
This chapter covers some of the most frequent blood tests that your doctor may order. Many of them can be done at the same time, with only one needle stick. The nurse or lab technicians can simply keep the needle in place and change the collection tubes. Then the samples can be sent to different departments in the lab for analysis. Unfortunately, there are times, especially when you are a patient in the hospital, that no sooner does the lab technician leave, than another comes in for another test and another needle stick! But as a rule, your doctors and nurses try to consolidate the tests so that doesn’t happen.
In the hospital, routine blood tests are usually drawn very early in the morning around 6 a.m. This is a source of great annoyance to many people, since they can’t imagine why samples must be taken at such an ungodly hour. The reason blood samples are collected so early is that it takes several hours for the lab to perform all the tests and get the results to the nurse’s station and into your chart. When the doctors come each day to review your chart and determine what medications, IVs, treatments, or tests you need, the results of blood tests are an important source of information.
Don’t hesitate to ask your nurse or doctor what blood tests are being done and why they are necessary. You also may want to know the results of the tests and what they indicate about your condition. Some people even keep notes about their blood tests -- which tests were done, why they were done, and the results.
Why Test Your Blood?
Blood is the fluid of life. It carries oxygen from your lungs to each and every cell of your body. It carries the glucose that all your cells need for energy and then carries off the waste products from the cells’ activities. Blood contains your body’s defense against infection and carries the means of repairing the vessels (arteries and veins) in which it flows. Blood maintains the balance of all the chemicals that are necessary for muscles and nerves to function and provides the communication and coordination for all your organs to work together. With these diverse functions, you can see why a small sample of your blood provides an amazing window into the health and functioning of every organ within you. A mere teaspoon or two, when analyzed by the lab, can tell a great deal about you.
Blood is made of cells and plasma. The blood cells are red cells, white cells, and platelets, which are all produced in your bone marrow. The plasma is a straw-colored fluid containing blood cells along with chemicals, enzymes, minerals, vitamins, hormones, and everything else your body needs to stay alive. A complete blood count (CBC) identifies the types, quantities, and characteristics of the different cells of your blood. A blood chemistry analyzes the plasma.
Bone Marrow -- The Blood Cell Factory
Bone marrow is the tissue within your bones where blood cells are made. In infants, all the bone marrow is capable of manufacturing blood cells. But in adults, blood cells are made only in the flat bones of the pelvis, sternum (breast bone), and skull.
The bone marrow is like a blood cell factory. It contains stem cells that have the capacity to evolve into all three types of blood cells. A stem cell can develop into a red cell and carry oxygen. Or it can evolve into a white cell and fight infection. Or it can evolve into a platelet, which can stop bleeding by forming a clot.
Bone marrow maintains the normal number of the three types of cells by replacing old cells as they naturally die off and increasing production of any kind of blood cell if there is a special demand for it. For instance, your bone marrow will step up production of white cells when you have an infection.
The bone marrow is a place where cells are dividing very quickly in order to keep up with your body’s constant demand for blood cells of all kinds. Since chemotherapy affects the cells that are dividing quickly (like cancer cells), it will temporarily affect your bone marrow. Unlike cancer cells, your bone marrow will recover and resume its normal production of blood cells.
Chemotherapy doesn’t affect the blood cells that are already in circulation, since they are not dividing. Only the production of new cells in the bone marrow is slowed down. Chemotherapy’s effect on your bone marrow usually shows up in your blood cell count about a week to ten days after your treatment. That is when you can see that the blood cells have not been replaced at the normal rate. But in another week or so, the number of blood cells in circulation will return to normal.
Your chemotherapy treatments are timed to allow your bone marrow to recover. Your doctor will always check your blood cell count before each treatment to be sure that your bone marrow is back on the job of producing blood cells.
Red Cells
Your red cells (also called erythrocytes) give blood its color. Ninety percent of each red cell is made up of hemoglobin, a substance rich in iron. The size, shape, and flexibility of red cells enable them to squeeze through the small openings between cells. The red cells’ purpose is to carry oxygen from your lungs to every corner of your body. If you have too few red cells because of blood loss or because your bone marrow is not working normally, then your body’s ability to carry oxygen is jeopardized.
When your red blood cell count is low, your heart has to work harder to cycle the remaining red cells at a faster rate to provide your body with the oxygen it needs. You may feel tired, since there may not be enough oxygen to keep up with the activity of your muscles. You may feel dizzy when you stand up after you have been sitting or lying down. You may chill easier or feel winded more easily after exerting yourself. These are all symptoms that your body needs more oxygen and more red cells to carry it.
Red cells have a relatively long life span (about three or four months). While the production of new red cells is slowed down for a few days after your chemotherapy, the fact that red cells live so long makes the problem much less severe. By the time more cells are needed, your bone marrow has long since recovered and has usually caught up.
A complete blood count (CBC) provides three measurements that reflect the adequacy of your red cells. They are the red blood cell count (RBC), hemoglobin (HGB), and hematocrit (HCT).
The red blood cell count is the number of red cells in a cubic millimeter of blood. The normal amount of red cells is about 4.5 to 6 million per cubic millimeter for men and 4 to 5.5 million per cubic millimeter for women. The normal values for women are less than for men because women who are menstruating lose a small amount of blood each month with their periods.
The hemoglobin (HGB) test measures the amount of this substance in a sample of blood. Hemoglobin is the part of a red cell that actually carries the oxygen, so an HGB test gives a good indication of the red cells’ ability to carry oxygen from the lungs to all the parts of your body. Normal hemoglobin for men is from 14 to 18 grams per 100 milligrams of blood. For women it is slightly less (12 to 16 grams).
The hematocrit (HCT) measurement determines what percent of the sample of whole blood contains red cells. Normally red cells comprise 42 to 54 percent for men and 38 to 46 percent for women.
If you have lost a lot of blood or your red blood production has been slowed down, then all three tests will be lower than normal. As your body turns up the production of red cells in the bone marrow or you receive a blood transfusion of red cells, all three values will rise.
What to Do When Your Red Cell Count Is Low
Many people get through chemotherapy without having a noticeable drop in the production of their red cells. Since the red cells live for so long and the bone marrow recovers in four to ten days, they are soon replaced. Depending on your general health, you may be able to cope with a mild drop in red cells without noticing anything more than fatigue.
If your red cells do get low, you’ll need to rest more and eat well -- especially foods high in iron. Your doctor may prescribe an iron supplement. If you don’t have enough cells to carry normal amounts of oxygen to your brain, you may feel dizzy for a few minutes when first standing up from a lying position. If that happens, you should get up slowly and take some deep breaths until the dizziness subsides.
Stimulating Red Blood Cell Production
A special hormone stimulates bone marrow to produce red cells. This hormone, erythropoietin, is normally produced by the kidneys in response to a drop in the oxygen carrying capacity of the blood. Erythropoietin works by stimulating the red blood cells to mature faster. A synthetic version of this hormone can be given by injection to speed up red cell production when it has been slowed by the effects of chemotherapy. If you have a severe drop in your red cells, you may require a blood transfusion.
White Cells
White blood cells (leukocytes) provide your body’s defense from infection. White cells are produced and stored in the bone marrow and are released when the body needs them. Once in the bloodstream, they circulate for only about twelve hours. Any inflammation or bacterial invasion will attract these cells, triggering them to leave the bloodstream and gather at the site of infection. There they surround the bacteria or other foreign body like an amoeba, stretching and wrapping themselves around it and then digesting it. White cells also help damaged tissue repair itself.
There are five kinds of white cells that are produced in the bone marrow. The first three (neutrophils, eosinophils, and basophils) have a granular appearance when seen under a microscope, and because of that they are called granulocytes. The two other types of white cells are lymphocytes and monocytes.
Neutrophils. Neutrophils are the most numerous white blood cells. They comprise 62 percent of all white cells and are the first to gather at an infection. Their job is to localize and neutralize bacteria. Each neutrophil can inactivate from five to twenty bacteria. When neutrophils are used up from fighting bacteria they rupture, and the contents of the ruptured cell attracts even more neutrophils, as well as increasing the blood supply to that area. The increased blood circulation can make an infected area appear redder and feel hotter than usual.
Eosinophils. Eosinophils are the white cells that respond to allergic reactions. Their job is to detoxify foreign proteins before they can harm the body. They also contain toxic granules that can kill invading cells and clean up areas of inflammation.
Basophils. Basophils, the rarest of the white cells, release histamine, which increases blood supply and attracts other white cells to the infected area. Basophils make it easier for white cells to migrate out of the blood into the damaged area. They also release heparin, which dissolves old clots.
Lymphocytes. Lymphocytes not only fight infection, but also provide you with immunity to certain diseases. For example, the measles virus is an antigen -- a substance that your body recognizes as foreign. Lymphocytes react to that foreign substance by forming antibodies. Antibodies are proteins which are designed to kill one specific antigen. There are many kinds of antigens, and your lymphocytes develop many different kinds of antibodies to attack them. These antibodies not only fight the foreign substance, but remember it so they can kill it whenever you are exposed to it again. Even if it is many years after your first exposure, the antibodies made by your lymphocytes remember the antigen and provide immunity.
Lymphocytes can be produced by the bone marrow or by other organs, such as the lymph glands, spleen, tonsils, or the thymus gland. They move back and forth between your blood and your lymph system. While many lymphocytes produce antibodies, others function as regulators for your immune response -- either helping it or suppressing it, depending on how well you are fighting an infection.
Monocytes. The last type of white blood cells are the body’s second line of defense because they do not respond as quickly as neutrophils. Their job is to move into an infected area to remove damaged or dying cells or cell debris. They contain special enzymes that are very effective in killing bacteria. Monocytes are produced in the bone marrow and initially circulate in your blood. Once they leave the blood, they go into the tissue and establish themselves in the lymph nodes, lungs, liver, or spleen.
Signs of Infection
All five kinds of white cells work together to fight infection. The usual signs of infection are swelling, redness, and warmth in the affected area and fever. These symptoms indicate that your immune system is working, fighting bacteria or other foreign organisms. The formation of pus in an infection is really a collection of old, dead bacteria and exhausted white cell debris.
Unlike red cells, which live for months, white cells have a life span of only three or four days, and the bone marrow is constantly producing new cells to replace them. It is the bone marrow’s production of white cells that is most vulnerable to the effects of chemotherapy. White cells that are already in circulation or in your tissues are not affected because they are not dividing. But when these cells die off and the reserves have been used up (within one week after your chemotherapy), your white count reaches its lowest point. This period, which is called the nadir, occurs about a week to ten days after you get your chemotherapy depending on what kind of chemotherapy you received. It is the time when you are most susceptible to infection. If you are exposed to bacteria during that time, your immune system may not be able to make as strong a response because there are just fewer white cells to respond. Following the nadir, your bone marrow will begin to catch up with white cell production and your count will recover. Your white count returns to normal about three weeks after your chemotherapy.
Your doctor expects your white count to drop temporarily and to recover before your next treatment. But he or she will always check your white count before you get chemotherapy again. If there is a delay in your white cells’ recovery, your doctor will delay your treatment for a few days and then check your count again. After several chemotherapy treatments it is not unusual for your white count to be a little sluggish in returning to normal.
What to Do When Your White Count Is Low
Many people who are getting chemotherapy weather the period of time when their white cell counts are low without problem. But you do need to take special precautions to avoid infection during this time. Here’s what to do:
Stay away from anyone who has a cold, flu, or other infection. Stay away from large crowds of people in an enclosed environment to avoid being exposed to coughs and sneezes. Keep your skin clean and dry. Moisture provides a breeding place for bacteria. You carry many germs on your hands, so be sure to wash your hands often, especially after using the toilet. Remind others (doctors, nurses, or anyone else helping with your care) to wash their hands too. Keep your teeth and gums clean as well. The food left on your teeth or under your dentures is a place bacteria could grow.
Drink plenty of fluids, since urinating frequently will keep your bladder from developing an infection.
Take special care to wash and disinfect any break in your skin and let your doctor know about all but the most superficial cuts.
Since it is the action of your white cells that causes inflammation, redness, or pus, you may not have these familiar signs of infections while your white cell count is low. You may have an infection and not even know it.
Check with your doctor if you have any signs of a cold, cough, flu, or fever during this time as well. He or she may want you to take an antibiotic to help your body fight infection more effectively.
When all your chemotherapy treatments are over, your body’s defenses will return to normal. But during this time, any exposure or risk of infections should be treated aggressively.
Stimulating White Blood Cell Production
Special proteins in your body called colony stimulating factor (CSF) stimulate the production of white cells. New techniques in genetic engineering have produced different forms of this protein that can be given by injection to counteract the effects of chemotherapy on the body’s immune system. There are several forms of CSF that increase different white cells such as granulocytes (G-CSF) and macrophages (M-CSF). When this stimulating factor is given, it causes your bone marrow to speed up the maturation of white cells and shortens the period of time when you are vulnerable to infection.
Not everyone getting chemotherapy will need this medicine to stimulate white blood cell production. But if there is a delay in bone marrow recovery or a high risk of infection, CSF can help your bone marrow recover sooner.
Infections
You are surrounded by a world you cannot see. All around you are bacteria, molds, yeasts, and viruses that can only be observed under a microscope. Everything you touch or eat and even the lining of your digestive system is teeming with microorganisms that could cause infection if they were to penetrate into your blood or tissues.
It is your intact skin and mucous membranes that usually keep these microorganisms from invading your blood system. It is only when these natural barriers are compromised that you risk infection. Your immune system then becomes your next line of defense, mobilizing to fight infection that has penetrated your skin or mucous membranes.
If an infection is severe or your immune system is compromised, you may need some help to fight it. Antibiotics are medicines that help your body fight bacteria infections. There are a number of different antibiotics, and some are more effective in killing certain bacteria than others. Your doctor may want to determine the exact bacteria that is causing your infection so he can prescribe the best antibiotic. He does this by ordering a culture.
Getting a Culture
You are probably familiar with throat cultures to determine what kind of organism is causing a sore throat. The doctor or nurse will take a sterile swab and wipe the back of your throat with it. Then the swab is smeared across a nutrient-rich gel and placed in a warm environment to encourage the bacteria to grow rapidly. In a day or two there are enough bacteria growing in the nutrient so that they can be examined under a microscope. The microbiologist in the lab can then see the exact bacteria causing the problem and determine which antibiotic will be most effective in killing it. When this test is done, it is called a culture (the process of growing the bacteria in a nutrient) and sensitivity (the process of determining which antibiotics are most effective in killing that bacteria). Viruses, molds, and yeasts can be cultured as well.
Bacteria and other organisms can be cultured from anything your body produces, such as urine, sputum, stool, or drainage from wounds. Blood cultures are quite common. If you have a fever or any other sign of infection, your doctor may want to determine if bacteria (or other organisms) are present in your blood. A sample of your blood is taken and put in an environment which encourages microorganisms to grow. Since your blood supply is so large, it’s often difficult to capture a particular organism in a small sample. Accordingly, you may have to have two samples of blood taken a few minutes apart to improve the chances of finding something.
If your infection is severe or your level of infection-fighting white cells is low, your doctor may not wait until the exact bacteria has been identified. After a sample of blood has been taken, he or she may want you to start taking an antibiotic right away. Usually your doctor will choose a broad spectrum antibiotic, named for its capacity to kill many different kinds of bacteria. In a few days, when the lab can identify the exact organism, your antibiotic may be changed to one that is more specific for that organism.
Fine-Tuning the Antibiotic
To fight infections successfully you need the correct antibiotic at the correct dose for a long enough time to assure that the infection is gone. That is why your doctor and nurse will remind you to take all of the antibiotic prescribed, even though the signs and symptoms of infection seem to disappear after a day to two. Most antibiotic pills are prescribed for a week to ten days. More severe infections may require IV antibiotics for a few days, and then, depending on the organism and your response, you may be switched to pills, tablets, or capsules.
The dose of some antibiotics must be fine-tuned to be sure it is effective against the infection, but not harmful to your body. The doctor, therefore, needs to know the antibiotic’s peak and trough. The peak is the greatest amount of medicine in your system (right after you receive it), and the trough is the least amount in your system (right before the next dose). To determine the peak and trough, your blood will be drawn twice, both before and after you get the medication. With this information, your doctor can adjust the dose to the right level for you.
Platelets
The cells in your blood that help to form a clot are called platelets. Platelets are produced in the bone marrow from a cell called a megakaryocyte.
Platelets help your body stop bleeding from knicks or cuts. They do that by collecting at the site of an injury and making the blood vessel constrict. Platelets then begin a series of chemical reactions that, along with other “clotting factors” in the liquid part of your blood, form a clot. After the vessel has healed and the clot has served its purpose, another series of chemical reactions cause the clot to dissolve so that the blood vessel is open again to carry blood.
Platelets are formed in large numbers, with up to 150,000 to 300,000 in each millimeter of blood. They live for about ten days in circulation. Chemotherapy slows down platelet production just as it slows down the production of all the other cells that are dividing frequently. The platelets in circulation are not affected because they aren’t dividing, but formation of the megakaryocytes which will become new platelets may fall behind temporarily. The period of time when your platelet count is the lowest (the nadir) comes about ten to fourteen days after your chemotherapy. Then your platelet count rises during the next two weeks until it is back to normal.
What to Do When Your Platelet Count Is Low
Many people get through all their chemotherapy treatments without being in danger of serious bleeding because of lack of platelets. Mostly it is a matter of being more careful to avoid injury and paying more attention to any bruise or abrasion you get.
During the nadir, you may find that you bruise more easily or bleed slightly longer from a cut or after a blood test. Here are a few things to watch for:
Check your skin all over for bruising or broken blood vessels. Check with your doctor if a bruise continues to increase in size or if you notice blood in your urine or bowel movements. Your mucous membranes are more likely to bleed as well. Even your normal toothbrushing and flossing may need to be altered during this time. Use a soft bristle brush and a more gentle technique. Plasma
Electrolytes
Plasma is the fluid in which the red cells, white cells, and platelets circulate. It contains many substances that are essential for your body to function. Sodium, potassium, chloride, calcium, magnesium, and so on must be present in your body in specific amounts. That’s because salts from these elements, when dissolved, can carry an electric charge that enables your heart, nerves, and muscles to work properly. These elements are called electrolytes.
Your kidneys help to regulate the balance of electrolytes by selectively eliminating or retaining these elements. For example, if you eat food that contains a high level of potassium, sodium, or calcium, your kidneys will keep what is needed and get rid of the excess. Chemotherapy treatments can temporarily affect your body’s ability to keep a normal balance of electrolytes. Your doctor may therefore need to adjust the amount of electrolytes you get in your IV.
Proteins
There are also proteins in plasma. These are large molecules, such as albumen and globulin, whose presence controls the flow of fluid from the blood system to the cells. Low levels of albumen can occur with malnutrition. This may cause water and plasma to leak into the surrounding tissue, causing swelling (edema).
Enzymes
Your heart and liver contain unique enzymes. If these organs have been damaged (from a heart attack or from liver damage), then the enzyme specific to that organ can be detected at higher levels than normal in plasma. When the levels of these enzymes drop back to normal, it indicates that the organ is recovering.>
Other Substances in Plasma
The levels of nitrogen, urea, and creatinine found in blood plasma indicate how well your kidneys are working. Since many chemotherapy drugs are excreted through your kidneys, your doctor will check the levels of these substances in your plasma before each treatment to determine the drugs and the doses that are safe and effective for you.
There are substances in plasma that are called clotting factors. They work with your platelets to form clots when needed and then work to dissolve the clots when they are no longer needed.
The amounts of glucose, protein, iron, and cholesterol in plasma can reflect your diet or digestion. An analysis of plasma can also provide early warning for diabetes, hormone imbalances, iron and vitamin deficiencies, or the risk of heart disease.
Testing plasma allows your doctor to check on how every organ is functioning. It is important to monitor not only how well the chemotherapy is working to kill cancer cells, but how the chemotherapy is affecting all the normal cells as well.
Tumor Markers
Research scientists are always looking for a simple blood test that will predict cancer at its earliest stage, as well as indicate how well the chemotherapy is working. This kind of test could also warn of recurrence long before there are any symptoms.
Although there is no current test that can accurately predict cancer’s occurrence or cure, there are a number of substances in your blood whose presence at certain levels is associated with particular kinds of cancers. These substances are called tumor markers. Their levels tend to rise if the cancer is growing and drop when the cancer is destroyed.
An important drawback of tumor markers is that a rise in the tumor marker may not always be caused by cancer, but by another disease or condition. For instance, the level of the antigen alpha fetoprotein (AFP) is associated with liver cancer and ovarian cancer, but the level may also rise with hepatitis or pregnancy. A rise in the blood level of carcinoembryonic antigen (CEA) is associated with cancer of the colon, pancreas, breast, or intestines, but a rise in CEA may also occur with pancreatitis, inflammatory bowel disease, or emphysema. A rise in the enzyme prostatic acid phosphatase (PAP) is associated with cancer of the prostate, bone, or multiple myeloma. But a rise in PAP is also possible with osteoporosis.
In other words, tumor markers are not foolproof in being able to predict the presence or absence of cancer. But they are one of many tools your doctor has in following your progress. Comparative X-rays, scans, and physical examinations, along with changes in your tumor markers, are all ways the doctor can tell how your treatment is progressing.
Interfacing with Other Health Care Professionals
Let your doctor know if you are planning any other medical treatments. Visits to the dentist, podiatrist, or chiropractor should be cleared by your oncologist first. During the period of time when you have fewer white cells or platelets than normal, you are more likely to bruise or bleed more easily and you are less resistant to infections. Your oncologist will advise you when other treatments are safe and the kind of precautions that other doctors need to take during this time. For the same reason, let other health professionals know that you are receiving chemotherapy so that they will consider this when planning and scheduling their treatments.
Coping
Blood tests are so common and useful in the diagnosis and treatment of diseases that medical people forget how stressful they may be for the patient. Here are some suggestions that may help you cope.
It helps if you can relax. If you are not in a panic, your veins are easier to find. Make sure that you are comfortable and your arm is well supported. When your arm stays still, the needle causes less pain.
If you can anticipate when the test will be done, you may want to ask for a warm blanket to wrap around your arms. The heat will make your veins swell and make it easier for the nurse or technician to take the blood sample.
When the test is over, apply pressure to the vein for at least five minutes. This is especially important if your platelet count is low and your body takes longer to form a clot. Applying pressure will minimize the amount of bruising and pain you have afterwards.
From The Chemotherapy Survival Guide, by Judith McKay, R.N. and Nancee Hirano, R.N., M.S.N.
