Section 1 General Assessment Blood Smears Monolayer Feathered Edge Body Background Increased Basophilia Cytoplasmic Fragments Infectious Agents Stain Precipitation Fibrin Skin Contaminants Blood Smears Distinctive Features: Blood smears have three major areas: (1) the thick inner area (body); (2) the monolayer; and (3) the feathered edge (the most external area). The inner area is the thickest area of the smear, and cells are usually too contracted, distorted, or poorly stained for reliable evaluation. The monolayer is the best area for cell morphology evaluation and differential cell counts, whereas the feathered edge is the best area to search for organisms (i.e., microfilaria), clumped platelets, and large atypical cells, neoplastic cells, or both. Blood smears should have a smooth transition in thickness from the proximal end to the distal end of the smear and have an adequate monolayer for evaluation of cell distribution and morphology. The monolayer is found within the distal half of the smear adjacent to the feathered edge and is luminescent when the unstained slide is held under indirect light. Diagnostic Significance: Initially, the entire smear should be quickly scanned using the 10 or 20× objective from the thickest region to the feathered edge. At this low magnification, blood films may be checked for staining, overall thickness, smooth transitions in thickness, cell distribution, adequacy of the monolayer area, and general appearance of the background. The feathered edge may be scanned at low power for platelet clumps, large parasites and large, atypical nucleated cells. A patient’s hematocrit may be crudely estimated by examining a blood smear at low magnification. This estimate assumes that smear thickness was not increased or decreased to compensate for anemia or hemoconcentration by increasing or decreasing the angle of the spreader slide. Blood films from nonanemic animals generally have red blood cells (RBCs) that are closely apposed in the monolayer as well as several RBC layers at the thick end of the smear that obstruct penetrance of most of the condenser light. In contrast, smears from animals that are moderately to markedly anemic usually have RBCs that are widely separated from one another in the monolayer and only one to two RBC layers in the thick end of the smear that allow considerable condenser light to penetrate. In smears prepared from hemoconcentrated specimens, the monolayer will occupy a relatively smaller zone and cells may be crowded and difficult to evaluate. Estimates should ultimately be checked against the patient’s measured hematocrit or packed cell volume (PCV). Monolayer Distinctive Features: In the monolayer, blood cells are present in a single layer. Cells should be side by side, but infrequently touching, and should not be distorted. Also, the monolayer should be devoid of large spaces without cells. Diagnostic Significance: The monolayer represents the limited region where cell morphology is most reliably evaluated. White blood cells (WBCs) should be fairly uniformly distributed within this region. WBC estimates, differential platelet estimates, and examination of WBC, RBC, and platelet morphologies should be done in the monolayer. In the monolayer, WBCs flatten and stain well, allowing good evaluation of cytoplasmic and nuclear detail. Also, inclusions such as rickettsial and viral inclusions may be readily identified. On a well-made blood smear, the total WBC and differential cell counts may be estimated or simply classified as low, normal, or high by examining the monolayer of the smear using the 40× or 50× objective, whereas platelet frequency is best estimated using the 100× objective. Plate 1-1 Normal Monolayer Next Topic Plate 1-1a Plate 1-1b Plate 1-1c Plate 1-1d Plate 1-1e Plate 1-1f Plate 1-1g Plate 1-1h Plate 1-1i Plate 1-1j Plate 1-1a Return to text. Return to image plate. Plate 1-1b Return to text. Return to image plate. Plate 1-1c Return to text. Return to image plate. Plate 1-1d Return to text. Return to image plate. Plate 1-1e Return to text. Return to image plate. Plate 1-1f Return to text. Return to image plate. Plate 1-1g Return to text. Return to image plate. Plate 1-1h Return to text. Return to image plate. Plate 1-1i Return to text. Return to image plate. Plate 1-1j Return to text. Return to image plate. Feathered Edge Distinctive Features: The feathered edge is the gently tapered end of the smear, located opposite the point of application of the blood drop. Diagnostic Significance: Large structures such as platelet clumps, microfilaria, cells containing infectious agents, and large, normal or neoplastic nucleated cells may be concentrated in this area. Thus, microscopic examination of the feathered edge is essential. If large platelet clumps are found at the feathered edge, this may account for a low or low-normal platelet estimate in the monolayer when evaluating platelet numbers and may also indicate that an instrument-generated platelet count may not be valid. Large neoplastic nucleated cells may be found in low or high numbers in this area, suggesting leukemia or circulating neoplastic cells from nonhematopoietic neoplasia (i.e., mast cell tumor and lymphoma). Large parasites, in particular, microfilaria, may be located in this region as well. Cells with intracellular organisms such as leukocytes containing Histoplasma organisms and RBCs containing Babesia spp. hemoparasites may concentrate in the feathered edge. A differential WBC count may be inaccurately skewed toward larger cell types if the differential is performed mostly at the feathered edge. Also, in the feathered edge, cells are often distorted, damaged, or ruptured, prohibiting reliable classification and morphologic evaluation. If excessive pressure is applied to the spreader smear during smear preparation, most of the nucleated cells will end up in the feathered edge of the smear. Estimates of the total WBC count and determination of percentages of the different types of leukocytes based only on examination of the monolayer of the smear will be inaccurate. A total WBC count may be attempted by evaluating the number of nucleated cells in the feathered edge and monolayer of the smear at 10× magnification. Plate 1-2 Normal Feathered Edge Next Topic Plate 1-2a Plate 1-2b Plate 1-2c Plate 1-2d Plate 1-2e Plate 1-2f Plate 1-2g Plate 1-2h Plate 1-2a Return to text. Return to image plate. Plate 1-2b Return to text. Return to image plate. Plate 1-2c Return to text. Return to image plate. Plate 1-2d Return to text. Return to image plate.< div class='tao-gold-member'> Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: 6: Extracellular Organisms 4: Platelets 5: Hematopoietic Neoplasia 3: White Blood Cells Stay updated, free articles. Join our Telegram channel Join Tags: Atlas of Canine and Feline Peripheral Blood Smears Jul 24, 2016 | Posted by admin in SMALL ANIMAL | Comments Off on 1: General Assessment Full access? Get Clinical Tree
Section 1 General Assessment Blood Smears Monolayer Feathered Edge Body Background Increased Basophilia Cytoplasmic Fragments Infectious Agents Stain Precipitation Fibrin Skin Contaminants Blood Smears Distinctive Features: Blood smears have three major areas: (1) the thick inner area (body); (2) the monolayer; and (3) the feathered edge (the most external area). The inner area is the thickest area of the smear, and cells are usually too contracted, distorted, or poorly stained for reliable evaluation. The monolayer is the best area for cell morphology evaluation and differential cell counts, whereas the feathered edge is the best area to search for organisms (i.e., microfilaria), clumped platelets, and large atypical cells, neoplastic cells, or both. Blood smears should have a smooth transition in thickness from the proximal end to the distal end of the smear and have an adequate monolayer for evaluation of cell distribution and morphology. The monolayer is found within the distal half of the smear adjacent to the feathered edge and is luminescent when the unstained slide is held under indirect light. Diagnostic Significance: Initially, the entire smear should be quickly scanned using the 10 or 20× objective from the thickest region to the feathered edge. At this low magnification, blood films may be checked for staining, overall thickness, smooth transitions in thickness, cell distribution, adequacy of the monolayer area, and general appearance of the background. The feathered edge may be scanned at low power for platelet clumps, large parasites and large, atypical nucleated cells. A patient’s hematocrit may be crudely estimated by examining a blood smear at low magnification. This estimate assumes that smear thickness was not increased or decreased to compensate for anemia or hemoconcentration by increasing or decreasing the angle of the spreader slide. Blood films from nonanemic animals generally have red blood cells (RBCs) that are closely apposed in the monolayer as well as several RBC layers at the thick end of the smear that obstruct penetrance of most of the condenser light. In contrast, smears from animals that are moderately to markedly anemic usually have RBCs that are widely separated from one another in the monolayer and only one to two RBC layers in the thick end of the smear that allow considerable condenser light to penetrate. In smears prepared from hemoconcentrated specimens, the monolayer will occupy a relatively smaller zone and cells may be crowded and difficult to evaluate. Estimates should ultimately be checked against the patient’s measured hematocrit or packed cell volume (PCV). Monolayer Distinctive Features: In the monolayer, blood cells are present in a single layer. Cells should be side by side, but infrequently touching, and should not be distorted. Also, the monolayer should be devoid of large spaces without cells. Diagnostic Significance: The monolayer represents the limited region where cell morphology is most reliably evaluated. White blood cells (WBCs) should be fairly uniformly distributed within this region. WBC estimates, differential platelet estimates, and examination of WBC, RBC, and platelet morphologies should be done in the monolayer. In the monolayer, WBCs flatten and stain well, allowing good evaluation of cytoplasmic and nuclear detail. Also, inclusions such as rickettsial and viral inclusions may be readily identified. On a well-made blood smear, the total WBC and differential cell counts may be estimated or simply classified as low, normal, or high by examining the monolayer of the smear using the 40× or 50× objective, whereas platelet frequency is best estimated using the 100× objective. Plate 1-1 Normal Monolayer Next Topic Plate 1-1a Plate 1-1b Plate 1-1c Plate 1-1d Plate 1-1e Plate 1-1f Plate 1-1g Plate 1-1h Plate 1-1i Plate 1-1j Plate 1-1a Return to text. Return to image plate. Plate 1-1b Return to text. Return to image plate. Plate 1-1c Return to text. Return to image plate. Plate 1-1d Return to text. Return to image plate. Plate 1-1e Return to text. Return to image plate. Plate 1-1f Return to text. Return to image plate. Plate 1-1g Return to text. Return to image plate. Plate 1-1h Return to text. Return to image plate. Plate 1-1i Return to text. Return to image plate. Plate 1-1j Return to text. Return to image plate. Feathered Edge Distinctive Features: The feathered edge is the gently tapered end of the smear, located opposite the point of application of the blood drop. Diagnostic Significance: Large structures such as platelet clumps, microfilaria, cells containing infectious agents, and large, normal or neoplastic nucleated cells may be concentrated in this area. Thus, microscopic examination of the feathered edge is essential. If large platelet clumps are found at the feathered edge, this may account for a low or low-normal platelet estimate in the monolayer when evaluating platelet numbers and may also indicate that an instrument-generated platelet count may not be valid. Large neoplastic nucleated cells may be found in low or high numbers in this area, suggesting leukemia or circulating neoplastic cells from nonhematopoietic neoplasia (i.e., mast cell tumor and lymphoma). Large parasites, in particular, microfilaria, may be located in this region as well. Cells with intracellular organisms such as leukocytes containing Histoplasma organisms and RBCs containing Babesia spp. hemoparasites may concentrate in the feathered edge. A differential WBC count may be inaccurately skewed toward larger cell types if the differential is performed mostly at the feathered edge. Also, in the feathered edge, cells are often distorted, damaged, or ruptured, prohibiting reliable classification and morphologic evaluation. If excessive pressure is applied to the spreader smear during smear preparation, most of the nucleated cells will end up in the feathered edge of the smear. Estimates of the total WBC count and determination of percentages of the different types of leukocytes based only on examination of the monolayer of the smear will be inaccurate. A total WBC count may be attempted by evaluating the number of nucleated cells in the feathered edge and monolayer of the smear at 10× magnification. Plate 1-2 Normal Feathered Edge Next Topic Plate 1-2a Plate 1-2b Plate 1-2c Plate 1-2d Plate 1-2e Plate 1-2f Plate 1-2g Plate 1-2h Plate 1-2a Return to text. Return to image plate. Plate 1-2b Return to text. Return to image plate. Plate 1-2c Return to text. Return to image plate. Plate 1-2d Return to text. Return to image plate.< div class='tao-gold-member'> Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: 6: Extracellular Organisms 4: Platelets 5: Hematopoietic Neoplasia 3: White Blood Cells Stay updated, free articles. Join our Telegram channel Join Tags: Atlas of Canine and Feline Peripheral Blood Smears Jul 24, 2016 | Posted by admin in SMALL ANIMAL | Comments Off on 1: General Assessment Full access? Get Clinical Tree
