Erythrocytes Flashcards
Name the stages of development in the erythrocytic series, using two systems of nomenclature.
Rubriblast, Prorubricyte, Rubricyte, Metarubricyte, Reticulocyte, and Erythrocyte.
Pronormoblast, Basophilic normoblast, Polychromatic normoblast, Orthrochromic normoblast, Polychromatophilic erythrocyte, and Erthyrocyte.
What is the last nucleated stage in development of the erythrocyte?
The metarubricyte/orthrochromic normoblast. The nucleus is “pitted” by the spleen.
What is asynchronous erythropoiesis?
Erythropoiesis in which the nucleus and cytoplasm mature at different rates. For example, in iron deficiency anemia the cytoplasm appears younger than the nucleus because of insufficient iron for hemoglobin synthesis and the mature erythrocytes are microcytic and hypochromic. In megaloblastic erythropoiesis the nucleus lags behind the cytoplasm in development because of a deficiency of vitamin B12 or folic acid and the mature erythrocytes are macrocytic.
Describe the normal mature erythrocyte.
A buff-colored biconcave disk, 6-8 microns in diameter, with an area of central pallor approximately 1/3 the diameter of the cell. The normal RBC is described as normocytic, normochromic. Cells greater than 9 microns in diameter are called macrocytes and those less than 6 microns are called microcytes. Cells whose central pallor is greater than 1/3 the diameter of the cell are described as hypochromic.
What is the best way to judge the size of an erythrocyte on a Wright-stained smear?
A normocytic RBC is approximately the same size, or slightly smaller, than the nucleus of a mature lymphocyte (8-9 microns). It is important to be in the correct area of the smear when evaluating RBC morphology–an area where the RBCs are just barely touching (approximately 200 RBCs in a 1,000x field). RBCs in the feathered edge appear macrocytic and lack central pallor. In the thick part of the smear RBCs appear microcytic and may seem to form rouleaux.
What is the first sign of accelerated erythropoiesis?
An increased reticulocyte count.
Define anisocytosis.
Variation in the size of the RBCs. This is a non-specific finding in anemia. If the RDW (red cell distribution width) is increased, anisocytosis should be seen on the blood smear.
Define poikilocytosis.
Variation in the shape of the RBCs. Some shapes are related to specific diseases such as sickle cells; others are nonspecific findings.
What are schistocytes?
They are RBC fragments that are seen with disseminated intravascular coagulation (DIC), hemolysis, burns, microangiopathic hemolytic anemia, and in patients with artificial heart valves.
What is a drepanocyte?
A sickle cell. These cells are seen in sickle cell anemia but not usually in sickle cell trait.
What is the significance of hemoglobin C crystals?
These hexagonal, dark-staining crystals with blunt ends (“Washington monuments”) are seen in some patients with hemoglobin C disease (CC). Frequently the cell membrane cannot be seen and the crystal appears to be free. Hemoglobin C crystals are not seen with hemoglobin C trait (AC),
What are dacryocytes?
Tear-drop shaped RBCs. They are seen in myelofibrosis and a variety of anemias.
How can crenated RBCs be differentiated from burr cells?
Burr cells may have more pointed projections as compared to the knobby projections of crenated cells, but the difference may be minimal. If the abnomality is seen in nearly all cells in the thin part of the smear, it is most likely artifact (crenation) due to slow drying of the smear or over-anticoagulation. Burr cells are seen in variable numbers throughtout the smear.
What is the clinical significance of burr cells?
They are seen with liver disease, uremia, hemolytic anemias, TTP, DIC, carcinoma of the stomach, and pyruvate kinase deficiency.
What is hypochromia?
A condition in which the area of central pallor is greater than 1/3 the diameter of the RBC.
What is a codocyte?
A target cell. This cell resembles a bull’s-eye, with a peripheral rim of hemoglobin and a dark central hemoglobin-containing area. Target cells are thin cells that appear as “Mexican hats” with a scanning electron microscope. They are a non-specific finding and occur in a variety of anemias, especially the hemoglobinopathies such as sickle cell anemia and hemoglobin C disease.
What is a leptocyte?
A variation of a target cell in which the central portion is not completely detached from the other membrane. Leptocytes are associated with hepatic disorders, iron deficiency anemia, and thalassemia.
What are spherocytes?
RBCs that are spherical rather than biconcave. They have a diameter of 6-7 microns, stain darkly, and have no central pallor. They are the result of damage to the RBC membrane and have a shortened life-span. They are seen with hereditary spherocytosis, hemolytic anemia, ABO hemolytic disease of the newborn (but not with Rh hemolytic disease of the newborn), burns, and following the transfusion of stored blood. A few spherocytes may also be seen in normal blood as part of the aging process. Spherocytes may be erroneously reported if one examines the feathered edge of the blood smear since RBCs in that area lack central pallor. In hereditary spherocytosis, the MCV may be normal to low and the MCHC slightly increased.
On a blood smear spherocytes appear small in comparison to normal RBCs. Explain how their MCV may be normal.
The appearance of the cells on the blood smear is a 2-dimensional representation. Since their diameter is decreased, spherocytes appear small. MCV is a 3-dimensional measurement of cell volume. Although spherocytes are small in diameter, their volume is normal because they are spherical rather than biconcave.
What are stomatocytes?
RBCs with slit-like central pallor. They may be found in liver disease, alcoholism, electrolyte imbalance, and hereditary stomatocytosis. They are often just an artifact.
What is the clinical significance of marked polychromasia?
It is a sign of accelerated erythropoiesis. If a new methylene blue stain is performed on the blood, the reticulocyte count will be elevated.
What is basophilic stippling?
Multiple irregularly-shaped purple inclusions throughout the cytoplasm of the RBC. IT may be fine or coarse. Basophilic stippling is due to aggregates of RNA and is associated with abnormal heme synthesis (fine) and lead poisoning (coarse).
Which RBC inclusion is associated with lead poisoning?
Coarse basophilic stippling.
What are Heinz bodies?
Round inclusions, 1-3 microns in diameter, attached to the RBC membrane. They stain with supravital stains but not with Wright stain. They are precipitated denatured hemoglobin and are seen with G-6-PD deficiency and drug-induced hemolytic anemia.
What are Howell-Jolly bodies?
Round nonrefractile purple inclusions, 1-2 microns in diameter, that are seen in RBCs post-splenectomy and in a variety of anemias. There is usually only one per cell. They are nuclear remnants (DNA).
What are siderotic granules?
Small irregular dark-staining iron granules near the peripheral of the RBC, seen in a Prussian blue stain. They are celled Pappenheimer bodies when seen on a Wright stain.
Which of the following can be seen on a Wright stained blood smear: Heinz bodies, Howell Jolly bodies, reticulocytes, siderocytes?
Only Howell-Jolly bodies. Heinz bodies and reticulocytes are seen with supravital stains–Heinz bodies with crystal violet and reticulocytes with new methylene blue or brilliant cresyl blue. Siderocytes are seen with Prussian blue. (On Wright stain, sideotic granules are referred to as Pappenheiner bodies).
Match the following abnormalities with an associated condition.
Abnormality and Conditions:
Basophilic stippling = Lead poisoning
Howell-Jolly bodies = Post-splenectomy
Heinz bodies = G-6-PD deficiency
Pappenheimer bodies = Sideroblastic anemia
Rouleaux = Multiple myeloma
Schistocytes = Disseminated intravascular coagulation, Spherocytes = Burns
What is the clinical significance of hypochromic microcytic RBC?
They are seen in iron deficiency anemia and thalassemia and sometimes with anemia of chronic disease.
Why is it important to report even a few oval macrocytes?
Because of their association with megaloblastic anemia.
Describe rouleaux.
RBCs arranged like stacks of coins. They are the result of a serum protein abnormality, either increased globulin or fibrinogen. They are often seen in patients with multiple myeloma. Rouleaux my be erroneously reported if one examines the thick part of the smear where the RBCs are overlapping. Artifactual rouleaux may also result from delay in spreading the drop of blood while making the smear.
In what ways will the RBC morphology of a newborn differ from that of an adult?
The RBCs of newborns are normally macrocytic and polychromatophilic. Newborns may have a few nucleated RBCs (1-5/100 WBCs) which are usually gone by 3-5 days of age. Reference ranges for WBCs, RBCs, hematocrit, hemoglobin, and reticulocytes are higher for newborns than for adults.
If a patient has an MCV of 110 fL and marked polychromasia, what other hematology test would be abnormal?
The reticulocyte count would be increased.
What effect does chronic alcoholism have on RBC morphology?
The MCV is usually elevated, target cells are common, and stomatocytes may be seen.
What changes occur in a blood specimen stored at room temperature?
The RBCs swell, increasing the MCV and hematocrit and decreasing the MCHC and erythrocyte sedimentation rate. The platelets and WBCs decrease and the osmotic fragility increases.
What are the time limits for performing tests on EDTA blood?
CBCs and reticulocyte counts can be performed on blood stored at room temperature for up to four hours, but blood smears should be prepared as soon after collection as possible. Erythrocyte sedimentation rates should be set up within two hours of collection if stored at room temperature or within six hours if refrigerated. The refrigerated specimen should be brought to room temperature prior to testing.
How should EDTA specimens be mixed prior to testing?
By gentle inversion at least 60 times or by mixing on a mechanical rotator for two minutes. Shaking or vortexing lyses the RBCs. Some mechanical rockers do not adequately mix blood that has settled.
What is a supravital stain?
A stain that stains unfixed cells in the living state. Examples are new methylene blue, brilliant cresyl blue, and crystal violet.
What stain is used for reticulocytes?
New methylene blue or brilliant cresyl blue.
Where are reticulocytes found after centrifugation of whole blood?
Just below the buffy coat. They are less dense than mature RBCs.
How is the reticulocyte count determined by the manual method?
Following staining with new methylene blue, 1000 RBCs are examined and the number containing reticulum noted. (Cells must contain two or more blue-staining inclusions to be counted as reticulocytes.) The percent is determined by dividing the number of retics over 1000 RBCs by 10 (moving the decimal point one place to the left). For example, if 100 reticulocytes are counted, the reticulocyte count is 10%. Alternately, a Miller disk can be used to facilitate counting. A miller disk is a calibrated disk that is placed in the microscope ocular. RBCs are counted in the small B square and reticulocytes in the large A square which is 9 times the area of the B square. A minimum of 300 RBCs are counted, providing an estimate of the reticulocyes per 2700 RBCs. Reitculocyte % = (reticulocytes in square A x 100) / (RBCs in square B x 9). Manual reticulocyte counts are imprecise, with coefficients of variation as high as 50%. Automated reticulocyte counts are now available on some hematology analyzers.
What other RBC inclusions are seen on a reticulocyte smear?
Howell Jolly bodies, Heinz bodies, and Pappenheimer bodies are all stained by supravital stains.
What is the reference range for reticulocytes in an adult when performed by the manual method?
0.5-2%. The reference range for newborns is 2-6%. By 1-2 weeks of age, normal values are the same as for adults.
How do reticulocytes stain on a Wright stain?
As polychromatophilic RBCs.
What is the significance of a high reticulocyte count?
Increased erythropoiesis. The reticulocyte count is always elevated in hemolytic states in which there is a normal compensatory bone marrow response.
What is the corrected reticulocyte count?
A calculated correction for anemia. The corrected reticulocyte count = reticulocyte % x (patient’s hematocrit (%) / normal hematocrit based on age and sex).
A 45 year old male with a hematocrit of 36% has a reticulocyte count of 5%. What is the corrected reticulocyte count?
Corrected reticulocyte count = 5% x (36/45) = 4%.
Why is the absolute reticulocyte count (ARC) becoming the preferred method of reporting reticulocytes?
It accounts for variation due to the number of RBCs. Reticulsytes x 10^9/L = [reticulocyte % x RBC count (10^12/L) x 1000] / 100. The referenge range is 25-75 x 10^9/L.
What are shift reticulocytes?
Reticulocytes that leave the bone marrow prematurely and mature in the circulation for longer than the normal maturation time of 1 day, leading to a falsely reticulocyte count.
What is the reticulocyte production index (RPI)?
A parameter that indicates the amount of erythropoiesis occurring when stress reticulocytes are present. The RPI takes into account the fact that prematurely released reticulocytes takes two days to mature instead of one. The RPI is calculated by dividing the corrected reticulocyte count by a maturation time correction factor based on the pattern’s hematocrit. The correction factor is obtained from a table. Normal bone marrow activity produces an RPI of 1. An RPI > 3 represents an adequate response to anemia by the bone marrow. An RPI < 2 is considered an inadequate response to anemia by the bone marrow.
A patient with a hematocrit of 35% has a corrected reticulocyte count of 5%. The maturation time correction factor for a hematocrit of 35% is 1.5. What is the patient’s RPI?
RPI = 5/1.5 = 3.3%
What is the most rapid, accurate, and precise method for reticulocyte counts?
Flow cytometry. Reticulocytes are counted on the basis of optical scatter or fluorescence after treatment with fluorescent dyes or nucleic acid stains. As many as 32,000 RBCs are counted, resulting in greatly improved precision. Automated retic counts eliminate problems inherent in manual reticulocyte count, such as stain variability, slide distribution errors, statistical sampling errors, and interobserver variability. Values are reported in absolute as well as relative terms. Reference ranges by flow cytometry are slightly higher than by the manual method. As more laboratories report automated retics, the corrected reticulocyte count and reticulocyte production index will be used less frequently.
Define PCV.
Packed cell volume, another name for hematocrit. It is the ratio of the volume of RBCs to the volume of whole blood.
How do the spin hematocrit and the hematocrit derived from an automated cell counter differ?
The automated hematocrit is a calculated value from RBC and MCV, therefore it may be somewhat lower than a spun hematocrit in which there is always some trapping of plasma within the RBC column. The difference is usually negligible unless there is a great deal of poikilocytosis and anisocytosis.
What is a normal hematocrit for a male?
42-52% (0.42-0.52 L/L). L/L is the SI unit.
What is a normal hematocrit for a female?
37-47% (0.37-0.47 L/L). L/L is the SI unit.
What is a normal hematocrit for a newborn?
53-65% (0.53-0.65 L/L). L/L is the SI unit.
What is the usual time and speed of centrifugation for a microhematocrit?
10,000 RPM for 5 minutes. Lower speeds or times lead to inadequate packing of the RBCs and a falsely elevated hematocrit. RPM should be checked periodically with a tachometer.
How can the safety of the hematocrit procedure be improved?
By using glass capillary tubes wrapped in puncture-resistant film and which do not require manually pushing one end of the tube into putty to form a plug.
While performing a manual hematocrit, the technologist observes an increased buffy coat. What is the significance of this observation?
The patient has an elevated WBC. It is important that the buffy coat not be included in the measurement of the RBC column or the hematocrit will be falsely elevated.
While reading a manual hematocrit a technician observes that the plasma is pink. How would this affect the hematocrit?
Hemolysis of the RBCs decreases the hematocrit . Blood should be redrawn and retested.
A phlebotomist had a difficult time obtaining blood from a patient and was only able to fill the EDTA tube one-fourth full. How would this affect the hematocrit?
Although the automated hematocrit would probably not be affected, a microhematocrit would be decreased because the RBCs would be crenated by the excess anticoagulant. Over-anticoagulation also decreases ESR, breaks up platelets, increases the platelet count, and causes degenerative changes in the WBCs.
A new phlebotomist had difficulty finding a vein in a patient and the tourniquet was left on for three minutes before the blood was obtained. How would this affect the hematocrit?
It would be elevated due to hemoconcentration.
