آزمايشگاه ايمونولوژي. كارشناس مسئول برنامه خانم قارداشي. چرا من بعنوان يك پزشك بايد ايمونولوژي عملي بدانم. روشهاي مختلف آزمايشگاهي را كه مي توان آناليت ها را اندازه گيري كرد بشناسيد از محدوديت هاي كار در آزمايشگاه آگاه باشيد پشت صحنه اعداد و ارقامي كه در مطب بدستتان مي رسد با خبر باشيد
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Requesting appropriate tests
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Interpretation of results
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Beakers hold and/orheatsolids or liquids that will not release gases when reacted, or are unlikely to splatter if stirred.
Very poor item to measure volume with (+/- 5% error!)
Note the total size capacity = 250 mL
(upper mark is 200 mL)Beaker
There are six sizes of beakers in your lab table for you to use:50, 100, 150, 250, 400, & 600 mL
Note the rubber coating to improve grip on the glass beaker - do not hold these in a burner flame.Beaker Tongs
Erlenmeyer flasks hold and/orheatsolids or liquids that may release gases during a reaction, or that are likely to splatter if stirred.
Note the size = 125 mL
Rarely used in first year chemistry, it is used for the mixing of chemicals. The narrow neck prevents splash exposure.
Also called round-bottom flasks
Flask tongs are used only to handle flasks – use beaker tongs for beakers.
A graduated cylinder is used to measure volumes of liquids; probably your best everyday measuring tool, there are three sizes in your desk: 10, 50 and 100 mL
*NOT to be used for heating or mixing chemicals
Note the rubber “bumpers”.Graduated Cylinder
Some graduated cylinders that are smaller may not have “bumpers”, but have reinforced glass rims.
The top plastic bumper ALWAYS stays at the top, to prevent breakage if it falls over.
10 mL has approx 6.62 mL
100 mL 52.7 mL
25 mL has 11.5 mL
18 x 150 mm
(25 x 200 mm) sometimes used
13 x 100 mm
The size is determined by the diameter across the top and the length of the test tube. Example: 13 mm x 100 mm (diameter) (length)
Test tubes are used to mix chemicals, and also used toheat chemicals in.
A test tube holder is useful for holding a test tube which is too hot to handle with your hands.
Knowing where to hold this piece of equipment is important.
Holding it here will keep your hand as far as possible from the fire, and prevent you from squeezing the holder and dropping the tube.
Rubber and cork stoppers are used to close test tubes and flasks, thus avoiding spillage or contamination.
Containers should NEVER be heated when there is a stopper in place – pressure will build up, and an explosion could occur.
Test tubes can be placed upside down on these pegs for drying.
Test tube racks are for holding, drying, and organizing test tubes in a vertical position, and are located in the side wall cabinets.
Small test tube brush
Caution: Forcing a large brush into a small test tube will often break the tube. Don’t worry about drying the inside of a tube or cylinder - Let them air dry instead of forcing a paper towel down inside.
Large test tube brush
Measuring pipettes are divided into:
The frosted band should
not be confused with
thicker colored rings or
colored dots, which are a
manufacturer’s code for
the maximum volume
of the pipette.
Remember, only blow-
out a serological pipette
if it has a frosted band
or two thin rings.
Roughly calibrated volumes of 1 and 2 ml can be transferred with the one piece plastic transfer pipettes which may be purchased as sterile or non-sterile units.OTHER PIPETTE TYPES
(Click on the picture to see
a movie on the SLC computer)
Touch the tip of the pipette to the side of the vessel containing the liquid to remove any adhering drops.
Step 1: Set the Volume
Pipettors – 3 Volumes:
Volume Adjustment Knob:
Digital Volume Indicator:
Step 1: (Continued) Read the Volume
How to Read the Volume Indicator:
Step 2: Attach the Disposable Tip
Example of tip sizes:
Attaching the disposable tip
Step 3: Depress the Plunger to the First Stop
Step 4: Immerse Tip in Sample
Step 5: Draw up the sample
To aspirate the sample into the tip, allow the pushbutton to return slowly and smoothly to the fully extended UP POSITION. NEVER LET THE PLUNGER SNAP UP! This draws the exact calibrated volume into the tip if the tip remains below the liquid surface during withdrawal.
Step 6: Pause
Wait a few seconds to ensure that the full volume of sample is drawn into the plastic tip. WAIT LONGER FOR LARGER VOLUMES. WAIT LONGER FOR MORE VISCOUS ("SYRUP-LIKE") SUBSTANCES.
Step 7: Withdraw the Tip
Remove the tip from the sample liquid. No liquid should remain on the OUTSIDE of the tip. Wipe away any droplets on the outside of the tip with a lint-free tissue, such as KIMWIPES, but only wipe droplets from the side of the tip. NEVER TOUCH THE TIP OPENING or you may absorb part of your sample.
Proper Droplet Removal
WRONG Droplet Removal
Step 8: Dispense the Sample
To dispense the sample from the pipette: a) Touch the tip end to the side wall of the receiving vessel and b) Depress the plunger to the FIRST STOP. c) Pause for at least one second-- 1-2 seconds for P-1000, 2-3 seconds for P-5000,
or longer for viscous liquids. d) Press the plunger to the SECOND STOP (the second point, of greater resistance,
at the bottom of the stroke) to expel any residual liquid in the tip (like "blowing
out" a glass pipette).
Step 9: Withdraw the Pipette
With the plunger fully depressed, withdraw the pipet from the receiving vessel carefully, sliding the tip along the wall of the vessel. Holding the tip against the side of vessel is especially important when transferring small volumes of liquid.
Step 10: Release the Plunger
Gently allow the plunger to return to the UP position. DO NOT allow it to SPRING BACK!
Step 11: Discard the Tip
Discard the tip by depressing the tip ejector button, as shown below. A fresh tip should be used for each sample to prevent sample carryover.
Press ejector button to discard tip.
For optimal reproducibility, use the following pipetting procedures:
(1) Consistent SPEED and SMOOTHNESS when you
press and release the PLUNGER
(2) Consistent pressure on the PLUNGER at the FIRST
(3) Consistent and sufficient IMMERSION DEPTH
(4) Nearly VERTICAL POSITIONING of pipette
(5) AVOID ALL AIR BUBBLES: Since the plastic pipette
shaft can be damaged if liquids are drawn beyond the
tip into the shaft
(6) NEVER lay the pipette on its SIDE nor INVERT the pipette if liquid is in the tip
A test is used in 50 people with disease and 50 people without. These are the results:
Specificity = 47/50 = 94%
Positive predictive value = 48/51 = 94%
Negative predictive value = 47/49 = 96%