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People living with leukemia need numerous blood tests before, during, and after treatment. When you give a blood sample, it may be tested in the laboratory in many different ways. Common blood tests for leukemia include complete blood count (CBC), genetic analysis of cancer cells, and minimal residual disease (MRD) — a measurement of how many leukemia cells remain in the body after treatment.
A CBC is one of the most frequently run tests for people with leukemia. The abbreviations that appear on a CBC results report can be confusing. Here is a breakdown of what is tested for and what CBC results can tell doctors.
A complete blood count shows the current number of cells in your blood and what types of cells they are. Blood is made of three main types of cells: red blood cells, white blood cells, and platelets.
Two other aspects of blood are usually tested in a CBC: hematocrit and hemoglobin. Hematocrit levels measure how much of your blood, by percentage, is currently made up of red cells. Hemoglobin indirectly measures the number of red blood cells in your blood. Hematocrit and hemoglobin help doctors better understand how well your RBCs are functioning at carrying oxygen to the tissues of your body.
On a CBC, red blood cell levels, white blood cell levels, and platelet levels are typically expressed as the number of cells per microliter of blood. Normal blood counts vary by individual. However, there are general ranges for men, women, and children.
The normal range of red blood cells per microliter is:
The normal range of white blood cells per microliter is:
Normal ranges for hematocrit levels are:
Hemoglobin is expressed in grams per deciliter (gm/dL). Normal ranges for hemoglobin are:
Platelet counts, regardless of age or gender, are considered normal at 150,000 to 400,000 per microliter.
White blood cells are also measured by ratio of WBC types — the white blood cell differential. There are five main types of white blood cells: neutrophils, eosinophils, lymphocytes, monocytes, and basophils. In a normal blood count, the WBC differential comprises:
Basophils and eosinophils make up the remainder.
What do abnormal results mean? For any given value, a result can be too high, too low, or unusual in relation to another value. For instance, the white blood cell differential may show an abnormal skew in WBC types. Abnormal results can indicate an issue in the bone marrow — where blood cells are made — or a variety of other disease processes. Although normal ranges are an expression of what is normal for the majority of healthy people, those with underlying conditions may have lower or higher ranges that are normal for them. For instance, in people living with heart disease, a higher-than-normal RBC count may be normal.
Your CBC results will help your doctor better understand how your leukemia and leukemia treatments are affecting your body. If results show your risk for serious side effects or complications is rising, your doctor may make a change in your leukemia treatment or prescribe other medications to address the problem.
If someone’s RBC, hematocrit, or hemoglobin counts are low, they are considered anemic. Anemia may occur when there are too few red blood cells being made in the bone marrow, or when the red cells are being destroyed by disease. Anemia can also be a consequence of low levels of iron, B12, or folate in the diet, along with other potential causes — including heavy or persistent bleeding. The primary symptoms of anemia are fatigue, weakness, and pale skin.
If your RBC count, hematocrit, or hemoglobin are low, your doctor may order a follow-up blood test called a reticulocyte count. Reticulocytes are immature RBCs. Counting them can help determine whether the problem is reduced RBC production or if the cells are being destroyed.
If red blood cell levels are too high, it may mean there is not enough oxygen in the blood. It can also indicate dehydration. In rare cases, a high RBC count may be due to polycythemia vera, a type of blood cancer in which RBCs are overproduced by the bone marrow. Overly high red blood cell counts are treated by drawing blood until the count is lowered. In some cases, medication might be used to reduce the amount of red cells.
A low platelet count, also referred to as thrombocytopenia, can indicate potential problems with blood clotting. Thrombocytopenia may occur when insufficient numbers of platelets are being made in the bone marrow, or platelets are being destroyed. In some cases, the body does not recognize the platelets as part of one's normal immune system and attacks them. Symptoms of low platelet count are bruising easily, excessive bleeding from minor cuts and scrapes, and bleeding from the nose or gums.
Transfusion is the most common way of treating low platelets, but your doctor may suggest other methods to reduce the chance of bleeding. If a blood test shows your platelets are low, your doctor may recommend avoiding common non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin, naproxen, or ibuprofen. These medications can interfere with the blood's ability to clot.
A high platelet count is called thrombocytosis. The two most common causes are a pre-existing condition or a bone marrow abnormality. High platelet counts can lead to stroke, heart attack, or a blood clot in a vein. Thrombocytosis is treated with medications that inhibit platelet production in bone marrow.
An overall low white blood cell count, also called leukopenia, means the body’s ability to fight infection is impaired. If there are fewer neutrophils in white blood cell counts, this is called neutropenia. When neutrophils are low, normal symptoms of infection may not show up, since those symptoms are specifically caused by the reaction of neutrophils fighting infection. This can lead to infections lasting longer and being harder to treat.
Low levels of lymphocytes mean the body cannot detect or fight viral infection as easily as usual, as lymphocytes are the cells that react first to viruses. If a test has shown you have low white counts and you develop a fever, you should seek immediate medical attention, as this may be the first sign of a serious problem.
Both leukemia and leukemia treatments can cause leukopenia.
Also known as leukocytosis, a high WBC count is a hallmark of some types of leukemia and other cancers of the bone marrow. High white blood cell counts can also indicate an existing infection or a dysfunction in the immune system.
If red cells, white cells, and platelets all have low levels, it is called pancytopenia. Pancytopenia is a sign, not a disease in and of itself. Pancytopenia can be caused by leukemia or other diseases of the bone marrow, a side effect of chemotherapy or radiation treatment, an autoimmune condition, or the result of an infection.
Different types of leukemia can be indicated by different blood test results. Acute lymphocytic leukemia (ALL) may cause a large number of immature white cells (lymphoblasts) in the blood, as well as low numbers of red blood cells and platelets. Acute myeloid leukemia (AML) may cause pancytopenia. In both chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and chronic myeloid leukemia (CML), mature cell counts are closer to normal, resulting in less severe symptoms than in acute leukemias.
Blood tests make many people with leukemia nervous. Results may show how well treatment is working or whether side effects from treatments are becoming more severe. “Waiting is the WORST,” one MyLeukemiaTeam member said.
Members have come up with a variety of ways to make the process easier. One member made sure they kept a copy of any results from their tests. “I make sure I have [a] copy of my blood work before I leave the doctor's office. I keep files on all tests and results from any doctors I see.”
Another MyLeukemiaTeam member advised others to make sure they ask about any blood test results they do not understand. “If you are ever concerned about your numbers, you should discuss them with the doctor and ask him or her to explain it better to you.”
When you join MyLeukemiaTeam, you gain a community of more than 7,000 people living with or caring for someone with leukemia. Blood count tests and results are a frequent topic of conversation.
Do you get anxious when waiting for blood count results? Do you have any tips for dealing with stress around blood tests? Comment below or start a conversation on MyLeukemiaTeam.