Preparation of blood smear

Blood smear is a very important method for examining blood cells and has a wide range of clinical applications. In order to have a full analysis and understanding of the condition of blood cells, it is necessary to make a blood smear. For ordinary people, understanding this aspect is useless, but in medicine it is very important and belongs to professional things. So, how is a blood smear made? Let’s take a closer look.

Place the slide in soap or laundry detergent and boil for 20 minutes; use hot water to wash away dirt such as soap and blood film, rinse repeatedly with tap water, and then rinse 3 to 5 times with distilled water. If necessary, soak it in 95% alcohol for 1 hour, then wipe it dry or bake it for later use. Soak the new glass slide in 95% alcohol or 10% hydrochloric acid for 24 hours, then wash it thoroughly with water.

2. Specimen collection

First, disinfect your ring finger with 75% alcohol. After the alcohol is dry, pierce the skin and allow the blood to flow out naturally. Do not squeeze it hard. Take a clean slide and place a drop of blood 4mm to 5mm away from the slide.

Be careful to hold the edge of the slide with your fingers and avoid touching its surface. Do not let the slide touch the skin at the blood collection site. After blood collection, push the slide quickly to prevent blood coagulation. If blood is collected from an anticoagulant tube, the blood must be fresh, otherwise it will cause damage to blood cells.

3 Preparation of blood smears

Slide requirements: 1.0 mm × 26 mm × (76 ± 0.5) mm; Slide pushing requirements: The slide edge should be neat and smooth; The quality of the blood smear is directly related to the size of the blood drop, the slide pushing angle, and the slide pushing speed. When pushing the slide, the bigger the blood drop, the bigger the angle, and the faster the slide pushing speed, the thicker the blood film, and vice versa. The uneven distribution of the blood film is mainly caused by uneven slide pushing, uneven force, and unclean glass slide. To make a uniform blood smear, you must apply even force and keep the angle constant. If the force is too light, the smear will be too thick to observe and cannot be pushed a second time; if the force is too heavy, the blood cells will be damaged. After production, it can be waved in the air to make it dry quickly to prevent the blood cells from shrinking. At the same time, after the blood film is dried, it is best to fix and stain it immediately to avoid contamination of the cells and dissolution. The effect will be poor after long-term storage. The blood film slices require: the blood film is uniform, as thin as a cicada's wing, the tail end is arc-shaped, and the blood film has different thickness areas at the head, body and tail. Pay attention to the patient's blood condition, such as the degree of anemia, blood viscosity, the number of white blood cells or nucleated cells, and adjust the film pushing technique.

4 Blood smear staining

The commercially available Wright's rapid stain is fast and clear for observing cell morphology, but the stain often destroys red blood cells. Therefore, the blood film must be covered with traditional Wright's stain first, then the rapid Wright's stain is added, and finally the buffer solution is added in sufficient amount and thoroughly mixed. Staining time: In summer, it is easier to use more buffer and staining solution, and the time should be relatively shorter, otherwise the staining solution will evaporate quickly and the dye will be deposited on the cells, making them difficult to identify and affecting the reading effect. If the dyeing is too light, you can re-dye it according to the original steps. When rinsing with tap water, rinse slowly to allow the sediment and staining particles of the staining solution to float away, allowing it to fully play a role in color separation, remove floating colors in cell staining, and show the nuclear structure and clear cell morphology. Wait until dry and examine under a microscope. If there is colored residue on the smear, it can be removed in three ways: First, add eosin-methyl blue dye solution to the smear, shake it slightly to dissolve the colored residue in methanol, wait for the methanol to evaporate, and then add distilled water or buffer solution. The second method is to place the blood smear in a water tank, keeping it level, and the color residue will overflow from the edge of the slide. The third method is to tilt the blood smear at 45 degrees, absorb 95% alcohol and slowly apply it on the surface of the smear until the alcohol flows down and turns blue, then rinse with clean water and dry it. If there is cedar oil on the smear, it can be wiped off with lens paper and then treated with alcohol. To determine whether the dye has achieved the desired dyeing effect, you can observe whether the dye has a layer of yellow metallic luster before rinsing it. If not, it means that the dyeing has failed.

The production of high-quality blood films requires inspectors to have solid basic skills and rich work experience. They must be proficient in the normal morphology of various cells and the specific changes in cell morphology. At the same time, they must have a clear understanding of the approximate distribution of different cells in the blood film. For an unsatisfactory blood film, they must analyze and determine the cause of failure. Peripheral blood smear examination usually includes the following items.

Erythrocyte morphology: Changes in erythrocyte size and hemoglobin content: microcytes, macrocytes, macrocytes, anisocytosis, hypochromicity, normochromicity, polychromophilicity. Changes in red blood cell morphology: target cells, spherocytes, ellipsoidal cells, stomatocytes, sickle cells, and abnormal red blood cells. Abnormal structures in red blood cells: including alkaline stippled red blood cells, Howell-Jolly bodies, Cabots rings, Pappenheimer bodies, etc.

Platelet morphology: Observe the size and distribution of the particles, whether they are distributed in clusters, and look for giant platelets and micromegakaryocytes. Therefore, every step of a good blood smear from cleaning to production and staining must be meticulous and completed patiently and carefully. This will allow for better observation of cell morphology and provide clinicians with reliable and true test reports, thus better serving the clinic.