The tuberculosis (TB) skin test and the measles, mumps and rubella (MMR) vaccination are two common procedures that most health care professionals should know how to perform. The TB test consists of an intradermal (into the skin) injection of a purified protein derivative (PPD) of TB in an attempt to illicit an immune response. An immune response indicates an exposure to TB. The MMR vaccination is simply a subcutaneous (into the fat under the skin) injection of three live attenuated (weakened) viruses to immunize an individual against said viruses.
Things You'll Need
- 1 ml tuberculin syringe
- 3 ml syringe
- 27 gauge, 5/8 in. needle
- 25 gauge, 1 in. needle
- Vial of PPD
- Vial of MMR vaccine
- Four alcohol pads
- Two 2 in. by 2 in. gauze pads
The MMR vaccination
Gather the MMR vaccine, 3 ml syringe, 25 gauge needle, two alcohol pads and a gauze pad. Unwrap the needle and syringe and assemble them by firmly pressing or twisting the hub of the needle onto the top of the syringe. Clean the rubber top of the vaccine vial with an alcohol pad and let it dry. Pull back the plunger of the syringe to .5 ml and push the needle into the rubber part of the vaccine vial. Inject the .5 ml of air into the vial to prevent negative pressure when withdrawing the vaccine. Turn the vial upside down and withdraw .5 ml of vaccine.
Prepare the injection site by gently cleaning with an alcohol pad. The preferred injection site for an MMR vaccination is the back of the upper arm half-way between the elbow and shoulder. Never touch the injection site after it has been cleaned or you will risk contamination and infection.
With your fingers pointing towards the elbow, grasp the skin at the injection site with your index finger and thumb about two inches apart. Lightly pull the skin toward the shoulder to create a small amount of tension and lift the skin off of the muscle. Hold the needle and syringe at a 45 degree angle to the skin with the bevel facing upward and quickly push the needle into the skin held between your fingers. Release the skin and use that hand to pull back on the plunger lightly. If any blood is pulled into the syringe, discontinue the process and try again. If no blood is present, push the plunger to inject the vaccine.
Remove the needle from the skin and hold a 2 inch by 2 inch gauze pad on the injection site to stop any bleeding and tape it in place. Dispose of the needle in an approved sharps container. Do not attempt to recap the needle.
The TB test
Gather the PPD, tuberculin syringe, 27 gauge needle, two alcohol pads and a gauze pad. Unwrap and assemble the needle and syringe. Clean the rubber top of the PPD vial with an alcohol pad and let dry. Pull back the plunger of the syringe to .1 ml and push the needle into the rubber part of the vial. Inject the .1 ml of air into the vial to prevent negative pressure and then turn it upside down and withdraw .1 ml of PPD.
Clean a spot about two inches in diameter on the anterior (palm) side of the forearm with an alcohol pad. This will be the injection site. Never touch the injection site after it has been cleaned or you will risk contamination and infection.
Pull the skin tight with your thumb from just under the injection site. Hold the needle and syringe at a 10 to 15 degree angle with the bevel of the needle facing upward. Gently insert the needle under the skin just until the bevel is covered. The needle should be shallow enough to see it under the skin. Slowly inject the .1 ml of PPD. A bubble should form at the test site. This is called a wheal and it should be about 10 mm in diameter. If no wheal forms, the injection must be repeated.
Remove the needle from the skin and blot any blood away with a gauze pad, but leave the site uncovered. Dispose of the needle in an approved sharps container. Do not attempt to recap the needle. Have the person being tested return between 48 and 72 hours later to have the test read. The test must be read in that 24 hour period.
Read the test by inspecting the site for an induration with your finger. An induration is a small hardened spot and will be easy to feel. The absence of an induration is a negative result. If an induration is present, mark it's borders on opposite sides with a pen. This must be exact. Redness or bruising should not be marked. Measure the space between the pen marks in millimeters and record the result. Depending on the person's risk factor and the size of the induration, it may indicate a positive test.
Tips & Warnings
- A positive TB test does not mean a person has TB. It only indicates an exposure to TB.
- A very small percentage of people will not become immune after one MMR vaccination. Less than 5 percent of people will have to receive a second vaccination.
- Although it is extremely rare, these injections have been know to cause allergic reactions. The person being vaccinated or tested should ideally be monitored for a reaction for 10 to 15 minutes after the injection.
- Injections are an invasive procedure and personal protective equipment should be worn to prevent exposure to blood-borne pathogens.
- "Delmar's Guide to Laboratory and Diagnostic Tests"; Rick Daniels; 2009
- "Tuberculosis: A Comprehensive Clinical Reference;" H. Simon Schaaf, Alimuddin Zumla; 2009
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