Hematology lab values Flashcards
Erythrocyte count
Male: 4.7-6.1 x 10^6 microL
Female: 4.2-5.4 x 10^microL
The RBC count is closely related to the hemoglobin and hematocrit levels and represents different ways of evaluating the number of RBC’s in the peripheral blood. It is repeated serially in patients with ongoing bleeding or as a routine part of the CBC. It is an integral part of the evaluation of anemic patients. A hormone name erythropoietin secreted mainly by the kidney, stimulates the production of RBC’s by the red bone marrow. Tissue hypoxia causes an increased secretion of erythropoietin. Toward the end of the RBC’s life, the cell membrane becomes less pliable; the ages RBC is then lysed and extracted from the circulation by the spleen. Abnormal RBCs have a shorter life span and are extracted earlier. Intravascular RBC trauma, such as that caused by artificial heart valves or peripheral vascular atherosclerotic plaques, also shortens the RBC’s life. an enlarged spleen, such as that caused by portal hypertension or leukemia, may inappropriately destroy and remove normal RBC’s from the circulation. When the value is decreased by more than 10% of the expected normal value, the patient is said to be anemic. Low RBC’s values are caused by many factors, including:
Hemorrhage (as in GI bleeding or trauma), hemolysis, dietary deficiency (as in iron or vitamin b12 or folic acid), Genetic aberrations (as in sickle cell anemia or thalassemia), Drug ingestion (as in chloramphenicol, hydantoins, or quinidine), Marrow failure (as in fibrosis, leukemia, or antineoplastic chemotherapy), chronic illness (as in tumor or sepsis), or other organ failure (as in renal disease). RBC counts greater than normal can be physiologically induced as a result of the body’s requirements for greater oxygen-carrying capacity (ex. high altitudes). Diseases that produce chronic hypoxia (ex. congenital heart disease) also provide this physiologic increase in RBC’s. Like the hemoglobin and hematocrit values, the RBC count can be altered by many factors other than RBC production. For instance, in dehydrated patients the total blood volume is contracted. The RBC’s will be more concentrated, and the RBC count will be falsely high. Likewise, in overhydrated patients the blood concentration is diluted and the RBC count per millimeter will be falsely low.
Erythrocyte indices
MCV-Mean corpuscular volume
80-95 mm^3
The RBC indices provide information about the size (MCV and Red blood cell distribution width), weight (MCH), and hemoglobin concentration (MCHC) of RBCs. This test is useful in classifying anemias.
MCV is an indicator of the size of the RBCs. If the MCV is lower than 78, the erythrocytes are microcytic, or smaller than normal. RBCs are microcytic in some types of anemias, such as iron deficiency anemia and lead poisoning. Thalassemia minor and thalassemia major (Cooley’s anemia), Which are genetic diseases, also cause microcytosis. if the MCV is higher than 100, the RBCs are macrocytic, or larger than normal. Macrocytic RBCs are characteristic of pernicious anemia and folic acid deficiencies. It is also common in liver disease and is sometimes used as a marker of recent alcohol intake. MCV also has been described as a predictor of mortality in clients with advanced cirrhosis. MCV that are normal are normocytic. Anemia due to acute blood loss results in normocytic anemia. The size of the RBCs is not enough to diagnose the reason for the anemia, but with other indices (MCH and MCHC), the anemia can be classified by size and color. Other tests, such as the peripheral blood smear, can identify the characteristic cell shapes of various pathologic conditions.
MCH-Mean corpuscular Hemoglobin
27-31 pg
Is the amount of Hgb present in one cell.
MCHC-Mean Corpuscular Hemoglobin Concentration
32-36 g/dL (32%-36%)
Is the measure of the average concentration or percentage of hemoglobin within a single RBC.
Erythrocyte Sedimentation Rate (ESR)
Male: up to 15 mm/hr
Female: up to 22 mm/hr
ESR is a measurement of the rate at which the red blood cells settle in saline solution or plasma over a specified time period. It is nonspecific and therefore not diagnostic for any particular organ disease or injury. Because inflammatory, neoplastic, infectious, and necrotic diseases increase the protein (mainly fibrinogen) content of plasma, RBCs have a tendency to stack up on one another, increasing their weight and causing them to descend faster. Therefore in these diseases the ESR will be increased. ESR provides the same information as an acute-phase reactant protein. That is to say that it occurs as a reaction to acute illnesses as described above. The ESR test occasionally can be helpful in differentiating entities or complaints. For example, in a patient with chest pain the ESR will be increased with myocardial infarction but will be normal with angina. The ESR is a fairly reliable indicator of the course of disease and therefore can be used to monitor disease therapy, especially for inflammatory autoimmune diseases (ex temporal arteritis, polymyalgia rheumatica). In general, as the disease worsens, the ESR increases; as the disease improves, the ESR decreases. If the results of the ESR are equivocal or inconsistent with clinical impressions, the C-reactive protein test is often performed. But ESR has several limitations: As mentioned, it is nonspecific, and it is sometimes not elevated in the face of active disease.
Hematocrit
Male: 42%-52% (0.42-0.52- volume fraction)
Female: 37%-47% (0.37-0.47- volume fraction)
values are slightly decreased in the elderly
The hematocrit or packed cell volume (Hct or PCV) is a fast way to determine the percentage of RBCs in the plasma. When the serum is centrifuged, the WBCs and platelets rise to the top in what is called the buffy coat. Because the heavier RBCs are packed in the bottom, the HCT is sometimes also called the packed cell volume. The Hct is reported as a percentage because it is the proportion of RBCs to the plasma. Note that the results are based on the assumption that the plasma volume is normal. An Hct is useful as a measurement of RBCs only if the hydration status of the client is normal. The Hct closely reflects the hemoglobin and RBC values. The Hct in percentage points usually is approximately three times the Hgb concentration in grams per deciliter when RBCs are of normal size and contain normal amounts of Hgb. Like other RBC values, the Hct can be altered by many factors other than RBC production. For instance, in dehydrated patients the total blood volume is contracted. The RBCs make up a greater proportion of the total blood volume, and the Hct measurement is therefore falsely high. Likewise, if the RBC is morphologically increased in size, the RBCs will make up a greater proportion of the total blood volume, and Hct will again be falsely high. Decisions concerning the need for blood transfusion are usually based on the Hgb or the Hct. In an otherwise healthy person, transfusion is not considered as long as the Hgb is above 8 g/dL or the Hct is above 24%. In younger people who can safely and significantly increase their cardiac output, a Hct of 18% may be acceptable. In an older individual with an already compromised oxygen-carrying capacity (caused by cardiopulmonary diseases), transfusion may be recommended when the Hct level below 30%.
Hemoglobin
Male: 14-18 g/dL (8.7-11.2 mmol/L)
Female 12-16 g/dL (7.4-9.9 mmol/L)
Critical values 20 g/dL
Values are slightly decreased in the elderly
Hgb serves as a vehicle for oxygen and carbon dioxide transport. The oxygen-carrying capacity of the blood is determined by the Hgb concentration. Hgb also acts as an important acid-base buffer system.
Methemoglobin
0.06-0.24 g/dL (9.3-37.2 micromole/L)
0.4%-1.5% of total hemoglobin
Critical values >40% of total hemoglobin
Methemoglobin is continuously being formed by the oxidation of heme iron to the ferric state. Normally, enzymes reduce the methemoglobin back to Hgb. Methemoglobin is not an oxygen carrier so increased amounts of it can lead to cyanosis. The inability to reduce methemoglobin at a normal state may be due to a congenital defect, but usually these clients have no symptoms. However, drugs such as the sulfonamides, acetaminophen, dapsone, and benzocaine sprays can cause increased levels of methemoglobin that can lead to cyanosis and obvious signs of respiratory difficulty. Newborns are more susceptible to methemoglobinemia because they have less of the enzyme needed to reduce methemoglobin. Co-oximetry can be done on an arterial blood sample to determine the amount of dysfunctional hemoglobin. Usually, less than 1% of the total Hgb is methemoglobin. Cyanosis may occur when levels reach 15%. Methemoglobinemia creates a rusty colored blood specimen. Treatment may include ascorbic acid or methylene blue intravenously.
Reticulocyte count
0.5%- 2% of total RBC
The reticulocyte count is an indication of the ability of the bone marrow to respond to anemia and make RBCs (erythropoietic activity). It is used to classify and monitor therapy of anemias. Normally there are a small number of reticulocytes in the blood stream. The reticulocyte count gives an indication of RBC production by the bone marrow. Increased reticulocyte counts indicate the marrow is releasing an increased number RBC into the bloodstream, usually in response to anemia. A normal or low reticulocyte count in a patient with anemia indicates increased RBC production compensating for an ongoing loss of RBCs (hemolysis or hemorrhage). Because the reticulocyte count is a percentae of the total number of RBCs, a normal to low number of reticulocytes can appear high in the anemic patient, because the total number of mature RBCs is low. to determine if a reticulocyte count indicates an appropriate erythropoietic (RBC marrow) response in patients with anemia and a decreased hematocrit, take Retic count % x Pt’s hematocrit/ Normal hematocrit and that will = Retic Index. The reticulocyte index in a patient with a good marrow response to the anemia should be 1.0. If it is below 1.0, even though the reticulocyte count is elevated, the bone marrow response is inadequate in its ability to compensate (as seen in iron deficiency, vitamin B12 deficiency, marrow failure). In these clinical situations, if iron or vitamin B12 is administered, the reticulocyte count will rise significantly to the point that the index equals or exceeds 1.0.
WBC count Adult and child >2
5000-10000/mm^3 (5-10 x 10^9/L) Critical Values < 2500 >30000.mm^3
The WBC count has two components. THe first is a count of the total number of WBCs (leukocytes) in 1 mm^3 of peripheral venous blood. The other component, the differential count, measures the percentage of each type of leukocyte present in the same specimen. An increase in the percentage of one type of leukocyte means a decrease in the percentage of another. Neutrophils and lymphocytes make up 75% to 90% of the total leukocytes. These leukocyte types can be identified easily by their morphology on a peripheral blood smear or by automated counters. The total leukocyte count has a wide range of normal values, but many diseases may induce abnormal values. An increased total WBC count (leukocytosis, WBC count > 10,000) usually indicates infection, inflammation, tissue necrosis, or leukemic neoplasia. Trauma or stress, either emotional or physical, may increase the WBC count. In some infections, especially sepsis, the WBC count may be extremely high and reach levels associated with leukemia. This is called a “leukemoid” reaction and quickly resolves as the infection is successfully treated. A decreased total WBC count (leukopenia; WBC count <4000) occurs in many forms of bone marrow failure (ex. following antineoplastic chemotherapy or radiation therapy, marrow infiltrative diseases, overwhelming infections, dietary deficiencies, autoimmune diseases). 5 types of WBCs may easily be identified on a routine blood smear. These cells, in order of frequency, include neutrophils, lymphocytes, monocytes, eosinophils, and basophils. The normal ranges for absolute counts depend on age, sex, and ethnicity. For example, normal ranges for absolute neutrophils for adult African American males is 1400 to 7000.
WBC Differential count
Neutrophils
55%-70%, 2500-8000 mm^3
The most common granulocyte, neutrophils, are produced in 7 to 14 days, and exist in the circulation for only 6 hours. The primary function of the neutrophil is phagocytosis. Acute bacterial infections and trauma stimulate neutrophil production is significantly stimulated, early immature forms of neutrophils often enter the circulation. These immature forms are called band or stab cells. This occurrence, referred to as a “shift to the left” in WBC production, is indicative of an ongoing acute bacterial infection.
WBC Differential count
Lymphocytes
20%-40%, 1000-4000 mm^3
These are divided into two types: T cells (mature in the thymus) and B cells (mature in the bone marrow). T cells are involved primarily with cellular-type immune reactions, whereas B cells participate in humoral immunity (antibody production). T cells are the killer cells, suppressor cells, and the T4 helper cells. The primary function of lymphocytes is to fight chronic bacterial infection and acute viral infections. The differential count does not separate the T and B cells but rather counts the combination of the two,
WBC Differential count
Monocytes
2%-8%, 100-700 mm^3
Are phagocytic cells capable of fighting bacteria similar to the way neutrophils do. Through phagocytosis, they remove necrotic debris and microorganisms from the blood. The monocytes produce interferon, which is the body’s endogenous immunostimulant. Monocytes can be produced more rapidly, however, and can spend a longer time in the circulation than the neutrophils.
WBC Differential count
Eosinophils
1%-4% 50-500 mm^3
see basophils
WBC Differential count
Basophils
0.5%-1%, 25-100 mm^3
also called mast cells and especially eosinophils are involved in the allergic reaction. They are capable of phagocytosis of antigen-antibody complexes. As the allergic response diminishes, the eosinophil count decreases. Eosinophils and basophils do not respond to bacteria or viral infections. The cytoplasm of basophils contains heparin, histamine, and serotonin. These cells infiltrate the tissue (ex. hives in the skins) involved in the allergic reaction and serve to further the inflammatory reaction. Parasitic infestations also are capable of stimulating the production of these cells.
