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  • BLOOD SMEAR EXAMINATION Making Blood smear

  • I- Preparation of blood smearThere are three types of blood smears: The cover glass smear.The wedge smear .The spun smear.The are two additional types of blood smear used for specific purposesBuffy coat smear for WBCs < 1.0109/L Thick blood smears for blood parasites .

  • WEDGE BLOOD SMEARSpecimen : EDTA blood within 2 to 3 hours & collected to the mark on tube.Not's : May change RBCs morphology such as Spiculated (crenated) cells if :Excessive amount of anticoagulant to specimenOld blood - long standing. Warm environment (room temperature) may hasten changes.

  • PROCEDUREplacing a drop of blood from mixed sample on a clean glass slide.Spreader slide using another clean glass slide at 30-40 degree angle.Control thickness of the smear by changing the angle of spreader slideAllow the blood film to air-dry completely before staining. (Do not blow to dry. The moisture from your breath will cause RBC artifact.)


  • The thickness of the spreadNotes:If the hematocrit is increased, the angle of the s preader slide should be decreased.2. If the hematocrit is decreased, the angle of the spreader slide should be increased.

  • CHARACTERISTICS OF A GOOD SMEARThick at one end, thinning out to a smooth rounded feather edge.Should occupy 2/3 of the total slide area.Should not touch any edge of the slide.Should be margin free, except for point of application.Note: As soon as the drop of blood is placed on the glass slide, the smear should be made without delay. Any delay results in anabnormal distribution of the white blood cells, with many of the large white cells accumulating at the thin edge of the smear.

  • COMMON CAUSES OF A POOR BLOOD SMEARDrop of blood too large or too small.Spreader slide pushed across the slide in a jerky manner.Failure to keep the entire edge of the spreader slide against the slide while making the smear.Failure to keep the spreader slide at a 30 angle with the slide.Failure to push the spreader slide completely across the slide.Irregular spread with ridges and long tail: Edge of spreader dirty or chipped; dusty slideHoles in film: Slide contaminated with fat or greaseCellular degenerative changes: delay in fixing, inadequate fixing time or methanol contaminated with water.

  • Examples of unacceptable smearsA: Blood film with jagged tail made from a spreader with achipped end.B: Film which is too thick C: Film which is too long, too wide, uneven thickness and made on a greasy slide.D: A well-made blood film.

  • Examples of unacceptable smears

  • BIOLOGIC CAUSES OF A POOR SMEAR Cold agglutinin - RBCs will clump together. Warm the blood at 37 C for 5 minutes, and then remake the smear.Lipemia - holes will appear in the smear. There is nothing you can do to correct this.Rouleaux - RBCs will form into stacks resembling coins. There is nothing you can do to correct this

  • Notes:Although this is the easiest and most popular methods for producing a blood smear, it does not produce a quality smear.

    The WBCs are unevenly distributed and RBC distortion is seen at the edges Smaller WBCs such as lymphocytes tend to reside in the middle of the feathered edge.

    2. Large cells such as monocytes, immature cells and abnormal cells can be found in the outer limits of this area.

    3. Spun smears produce the most uniform distribution of blood cells.


  • II- Fixing the filmsTo preserve the morphology of the cells, films must be fixed as soon as possible after they have dried.

    It is important to prevent contact with water before fixation is complete.

    Methyl alcohol (methanol) is the choice, although ethyl alcohol ("absolute alcohol") can be used.

    Methylated spirit (95% ethanol) must not be used as it contains water.

    To fix the films, place them in a covered staining jar or tray containing the alcohol for 2-3 minutes. In humid climates it might be necessary to replace the methanol 2-3 times per day; the old portions can be used for storing clean slides.

  • III. Staining the filmRomanowsky staining: Romanowsky stains are universally employed for staining blood films and are generally very satisfactory.There are a number of different combinations of these dyes, which vary, in their staining characteristics.May-Grunwald-Giemsa is a good method for routine work.2. Giemsa stain is thought to produce more delicate staining characteristics.Wright's stain is a simpler method.4. Leishman's is also a simple method, which is especially suitable when a stained blood film is required urgently or the routine stain is not available (e.g. at night). 5. Field's stain is a rapid stain used primarily on thin films for malarial parasites.

  • Principle The main components of a Romanowsky stain are:A cationic or basic dye (methylene blue or its oxidation products such as azure B), which binds to anionic sites and gives a blue-grey color to nucleic acids (DNA or RNA), nucleoproteins, granules of basophils and weakly to granules of neutrophilsAn anionic or acidic dye such as eosin Y or eosin B, which binds to cationic sites on proteins and gives an orange-red color to hemoglobin and eosinophil granules.

    pH value of phosphate buffer is very important.

  • Eosinophilic granulesBasophilic granulesBlue nucleus

  • Staining procedure (Leishmans stain) Thin smear are air dried.Flood the smear with stain. Stain for 1-5 min. Experience will indicate the optimum time. Add an equal amount of buffer solution and mix the stain by blowing an eddy in the fluid.Leave the mixture on the slide for 10-15 min. Wash off by running water directly to the centre of the slide to prevent a residue of precipitated stain.Stand slide on end, and let dry in air.

  • Staining procedure Thin smear are air dried.Flood the smear with stain. Stain for 1-5 min. Experience will indicate the optimum time. Add an equal amount of buffer solution and mix the stain by blowing an eddy in the fluid.Leave the mixture on the slide for 10-15 min. Wash off by running water directly to the centre of the slide to prevent a residue of precipitated stain.Stand slide on end, and let dry in air.


  • CAUSES & CORRECTIONToo Acid Stain:insufficient staining timeprolonged buffering or washingold stainCorrection:lengthen staining timecheck stain and buffer pHshorten buffering or wash time

  • Too Alkaline Stain:thick blood smearprolonged staininginsufficient washingalkaline pH of stain componentsCorrection :check pHshorten stain timeprolong buffering time


  • PRINCIPLE White Blood Cells.Check for even distribution and estimate the number present (also, look for any gross abnormalities present on the smear).Perform the differential count.

  • PRINCIPLE Red Blood Cells, Examine for: Size and shape. Relative hemoglobin content. Polychromatophilia. Inclusions. Rouleaux formation or agglutinationPlatelets. Estimate number present. Examine for morphologic abnormalities.

  • PROCEDURESObservations Under 10Check to see if there are good counting areas available free of ragged edges and cell clumps.Check the WBC distribution over the smear.Check that the slide is properly stained.Check for the presence of large platelets, platelet clumps, and fibrin strands.

  • OBSERVATIONS UNDER 40X : WBC ESTIMATESUsing the 40 high dry with no oil.Choose a portion of the peripheral smear where there is only slight overlapping of the RBCs. Count 10 fields, take the total number of white cells and divide by 10.To do a WBC estimate by taking the average number of white cells and multiplying by 2000.

  • OBSERVATIONS UNDER 100: PLATELET ESTIMATESUse the oil immersion lens estimate the number of platelets per field.Look at 5-6 fields and take an average.Multiply the average by 20,000.Note any macroplatelets.Platelets per oil immersion field (OIF)20 platelets/OIF = increased


  • OBSERVING AND RECORDING NUCLEATED RED BLOOD CELLS (NRBCS)If 10 or more nucleated RBC's (NRBC) are seen, correct the White Count using this formula:Corrected WBC Count = WBC x 100/( NRBC + 100)Example : If WBC = 5000 and 10 NRBCs have been countedThen 5,000 100/110 = 4545.50The corrected white count is 4545.50.

  • MANUAL DIFFERENTIAL COUNTSThese counts are done in the same area as WBC and platelet estimates with the red cells barely touching.This takes place under 100 (oil) using the zigzag method.Count 100 WBCs including all cell lines from immature to mature.Reporting resultsAbsolute number of cells/l = % of cell type in differential x white cell count

  • Observing direction:Observe one field and record the number of WBC according to the different type then turn to another field in the snake-liked direction*avoid repeat or miss some cells


  • LEUKOCYTOSISLeukocytosis, a WBC above 10,000 is usually due to an increase in one of the five types of white blood cells and is given the name of the cell that shows the primary increase. Neutrophilic leukocytosis = neutrophilia 2. Lymphocytic leukocytosis = lymphocytosis 3. Eosinophilic leukocytosis = eosinophilia

    4.Monocytic leukocytosis =monocytosis

    5.Basophilic leukocytosis = basophilia


    Diameter:12-16Cytoplasm : pinkGranules: primary secondaryNucleus: dark purple blue dense chromatin



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