| The M:E ratio represent the ratio of nucleated bone marrow cells with respect to: | View Page |
| Match each of the following: | View Page |
| Preparation of Concentrated Smears In some laboratories the anticoagulated sample is used to prepare concentrated smears. Placing the fluid in a Wintrobe tube and centrifuging it separates the sample into four layers:fat and perivascular cellsplasmabuffy layer - myeloid and nucleated erythroid cellserythrocytesThe volume of each layer is measured using the scale on the Wintrobe tube and then the percentage of each layer is calculated. Next the plasma is removed and a smear is made from the buffy coat and top of the red cell layer. Either the manual push method or cytospin technique may be used to make the smears. They may be stained with a variety of cytochemical stains. Concentrated smears are used to examine cell morphology and demonstrate the presence of abnormal cells when the marrow is hypocellular. The smears cannot be used for differential counts or evaluation of cellularity. | View Page |
| Location of Cells within Cord Within the hematopoietic cords each cell line has a specific location for development.
Erythroid precursors are located near a venous sinusoid and cluster around a macrophage. This is referred to as an erythroblastic island. Developing red cells obtain iron needed for hemoglobin production from macrophages.
Megakaryocytes are also located close to a venous sinus. They extend their cytoplasm in fingerlike projections through the sinus wall in order to release their platelets directly into the blood in the sinus.
Immature granulocytes lie within the hematopoietic cords.
The metamyelocyte stage is the first stage of the granulocyte series that is motile and able to move toward the sinus area. Mature neutrophils, eosinophils and basophils enter the sinusoidal blood through the basement membrane. As maturing erythrocytes also move toward the sinus wall any remaining nuclei are lost as the red cells move through small openings in the cells lining the sinus wall. | View Page |
| Changes in Cell Distribution Changes in the distribution of cells in the marrow are most apparent in the first month of life. At birth, granulocyte cells predominate. The myeloid to erythroid (M:E) ratio is somewhat higher in newborns and during infancy than it is later on in childhood and in adults. | View Page |
| The young cells that can be found surrounding a macrophage are: | View Page |
| Iron Storage Site The site of iron storage in the bone marrow is the macrophage. This is a bone marrow smear showing a macrophage containing near the top of the smear showing clumps of blue-staining material, which is iron. Notice the number of young red cells (erythroid precursors) clustered around the iron in the lower portion of the slide. | View Page |
| Examination of Wright-Giemsa Stained Bone Marrow Examination of Wright-Giemsa stained bone marrow preparation involves examination under low power (10X objective) high power (40-50X objective )and oil immersion (100X objective). Low power examination: Assess quality of smear, assess number of megakaryocytes.Assess myeloid to erythroid ratio.Evaluate morphology and do differential count. | View Page |
| Low Power Magnification This smear is shown under low power (10x objective) magnification. The reddish cells in the background are mature red blood cells. The dark dots are nucleated erythroid and myeloid precursors. The large dark dot in the middle is a megakaryocyte. Normally, about 5 to 10 megakaryocytes are seen per microscopic field at low power magnification. Clusters of megakaryocytes usually indicate megakaryocytic hyperplasia. Less than 2 megakaryocytes per low power field may mean megakaryocytic hypoplasia. | View Page |
| Normal M:E Ratio The normal M:E ratio in adults varies from 1.2:1 to 5:1 myeloid cells to nucleated erythroid cells. An increased M:E ratio (6:1) may be seen in infection, chronic myelogenous leukemia or erythroid hypoplasia. A decreased M:E ratio (<1.2-1) may mean a decrease in granulocytes or an increase in erythroid cells. M:E ratios are somewhat higher in newborns and infancy than in later childhood and in adults. It is important to note that lymphocytes, monocytes and plasma cells are not included in the M:E ratio. | View Page |
| Percentages of Myeloid and Erythroid Precursors The normal cellularity has been described as 50%. Therefore, about 40% of the cells would be myeloid (granulocytic) and 10% erythroid. Since cellularity and distribution may vary from one area of the marrow to another, an acceptable range for percentages of myeloid and erythroid cells would be:Myeloid cells 25-55%Erythroid cells 8-14% | View Page |
| Normal M:E Ratio A normal M:E ratio is depicted in this slide. Notice that the area shown is a portion of the slide near a particle or spicule of marrow where the cells are numerous. The morphology can still be clearly differentiated. The small dark cells scattered throughout the slide are erythroid cells, while the larger, lighter staining cells are myeloid cells. The normal M:E ratio varies from 1.2 to 5 myeloid cells for each erythroid cell. | View Page |
| Differentiating Myeloid from Erythroid Cells To help you learn to differentiate myeloid cells and erythrocytes under high power, some slides showing thinner areas than would normally be used for determination of the M:E ratio have been included. Erythroid cells are shown at the arrows. | View Page |
| Normal M:E Ratio Another example of a normal M:E ratio in a thicker, more representative area of the smear. The cells shown by the arrows are erythroid precursors. | View Page |
| Increased M:E Ratio An increased M:E ratio is present in this field. Many more myeloid cells are present than erythroid cells. The M:E ratio is approximately 25:1. | View Page |
| Decreased M:E Ratio An example of a decreased M:E ratio in a thin area of the smear. A decreased M:E ratio means that the myeloid cells are decreased in number when compared to the erythroid cells. Approximate ratio is 1:2. | View Page |
| Another Example of Decreased M:E Ratio Another example of a decreased M:E ratio in a representative area of the slide. Numerous erythroid precursors are shown by the arrow. | View Page |
| Estimating Myeloid to Erythroid Ratio When examining a bone marrow smear, estimate the M:E ratio for each of ten fields and take the average as the estimated M:E ratio. | View Page |
| Representative Counting Field The actual cell count is performed using the oil (100x) objective. This oil immersion field shows a representative counting field. Four granulocytes, a prorubricyte, and two rubricytes are completely visible here. 100 to 500 nucleated cells are generally counted,depending on the cellularity of the smear, and only cells completely visible in the field should be included in the count. | View Page |
| High Power Examination High power (40x objective) examination can be used to estimate the myeloid-to-erythroid ratio. The erythrocytes are nucleated, immature erythrocytes. Under high power, nucleated red cells appear to have a dark purple nucleus as opposed to the lighter staining nucleus of the myeloid or granulocyte series. Lymphocytes also have a dark staining nucleus and some may be erroneously included in the erythroid estimate. In the normal marrow these numbers are insignificant. | View Page |