How are PPD tests measured?
The reaction should be measured in millimeters of induration (palpable, raised, hardened area or swelling).
- Do not measure erythema (redness).
- The indurated area should be measured across the forearm (perpendicular to the long axis).
Can a TB test be 0 mm?
A person with a positive reaction should be referred for a medical evaluation for latent TB infection and appropriate follow-up and treatment if necessary. A measurement of 0 mm or a measurement below the defined cut point for each category is considered negative.
What is a positive TB test reading?
In a healthy person whose immune system is normal, induration greater than or equal to 15 mm is considered a positive skin test. If blisters are present (vesiculation), the test is also considered positive. In some groups of people, the test is considered positive if induration less than 15 mm is present.
How do you read a TB test?
READING THE TUBERCULIN SKIN TEST Examine the TST site 48 to 72 hours after the TST is administered. If the TST is not read within 72 hours, the result is invalid and must be repeated, unless there is 10 mm or more of induration present. Repeat TST can be done immediately.
Which needle size and gauge would you use for a PPD skin test 0.1 mL is today?
Administer the test dose (0.1 mL) of TUBERSOL with a 1 mL syringe calibrated in tenths and fitted with a short, one-quarter to one-half inch, 26 or 27 gauge needle.
What is a positive PPD test?
The most commonly used skin test to check for TB is the PPD — purified protein derivative. If you have a positive PPD, it means you have been exposed to a person who has tuberculosis and you are now infected with the bacteria (mycobacterium tuberculosis) that causes the disease.
How do you read a PPD test?
Understanding your PPD skin test results. If the area of skin where you received the PPD injection isn’t swollen or is only slightly swollen 48 to 72 hours after the injection, the test results are negative. A negative result means that you most likely haven’t been infected with the bacteria that cause TB.