Align-ju STUDENT
Change PPE if you leave the room , and between patients or if your PPE has been in contact with any bodily fluids . Clean the environment before and after use with an appropriate disinfectant to prevent infection via fomite transmission . Fomites are inanimate objects that are likely to carry infection . In practice , clothing , utensils and furniture are all considered to be fomites . It is a good idea for a member of practice staff to prepare and organise an in-practice continuing professional development ( CPD ) session on infection control , as education is vital in preventing contamination . It is important to make everyone aware of how infections spread , the precautions to take , and how to implement , follow and monitor an infection control policy . This understanding will increase compliance and improve the hygiene status of the practice .
Blood smear
Once a blood sample has been taken from the patient , the VS may request a blood smear . This can be carried out in-house or in a laboratory . Blood is spread across a glass slide and examined under a microscope to inspect the red and white blood cells . ( Read the guide to interpreting blood panels from p . 44 of this issue of VNJ for further information on blood film examination .)
Preparing a blood smear
• Wear PPE consisting of gloves as a minimum .
• Clean the slide and dry it with a lint-free tissue to prevent marks or dust , which can interfere with the quality of the smear .
• Gently mix the ethylenediaminetetraacetic acid ( EDTA ) sample by inverting the tube a few times .
• Insert a plain capillary tube into the EDTA sample and draw up a small amount of blood .
• Place a gloved finger over the top of the capillary tube or keep it horizontal to prevent blood leakage .
• Place a small dot of blood at one end of the glass slide and ensure the used capillary tube is discarded into the clinical waste bin .
• Place a spreader slide at the opposite end of the slide to the blood and draw the spreader slide back to the drop of blood at a 45 ° angle . Allow the blood to spread evenly across the spreader .
• Push the spreader away from the blood in one smooth motion to produce even coverage of blood on the slide .
• Air dry the slide , label it , and check and comment on the quality of the smear .
Ideally , the slide should look like a thumbprint with a feathered edge of equal thickness [ 1 ] . Common blood smear faults and their causes are shown in Table 1 .
Table 1 . Common blood smear faults and their causes .
Fault Too thick Too thin
Thin and thick bands on the smear
Streaks at the length of the smear , near the tail
Spots on slide where blood is absent
Narrow , thick blood smear
After producing a blood smear , the VS may ask for the slide to be stained with Diff-Quik stains before microscopic examination . Before doing this , put on some gloves . Dip the dry blood smear into the fixative methanol ( pale blue solution ). Allow excess fluid to drain back into the jar . Do the same process with the eosin solution , stain I ( red solution ), and with the methylene blue solution , stain II ( purple solution ). Rinse the slide with distilled water and place vertically to dry .
Microscopy is an important skill in diagnostic testing , and you may be asked to locate certain blood cells , urinary crystals and parasites by the VS .
Setting up the microscope
Cause Too much blood on slide
Not enough blood was used for the smear
Hesitation marks
Dried blood on the end of the spreader , irregular edge to the spreader slide , or dust on the slide or in the blood sample [ 2 ]
Grease on the slide [ 2 ]
Smear made before the blood has run across the spreader edge , or one surface of the spreader is lifted before spreading [ 2 ]
• Turn down the rheostat ( the light intensity switch ) to the lowest setting . Plug in the microscope and switch it on .
• Lower the mechanical stage to its lowest point . Adjust the substage condenser and ensure it is just below the stage .
• Wear PPE ( gloves as a minimum ) when handling the sample slide . Place the slide on the microscope facing the right way up .
• Select the lowest-power lens to begin with (× 4 ).
• Rack up the stage so it is just below the objective lens , ensuring they do not touch . ( Do not look down the eyepiece when racking up the stage .)
• Look down the eyepiece and adjust as necessary , so only one image is seen .
Volume 38 ( 6 ) • December 2023
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