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A PPD is considered positive if it meets a specific criteria 48-72 hours after it's administered, color is not one of the criteria used to determine if the test is negative or positive. A PPD site can undergo a lot of changes in the time between administration and reading. CDC | TB | Fact Sheets - Tuberculin Skin Testing for TB
Whenever I have mine done, i do get a large area of redness that will last a couple weeks before it finally fades away completely. What is measured is if there is a bump or raised reaction. It was hard not to scratch at it, and the dr's office also told me that wearing long sleeves or rubbing against things like tables can cause that redness, but shouldn't affect your results.
I tell my patients to ignore what the PPD site looks like for the first two days after I place it because it may go through a variety of shapes, sizes and colors: I tell them to be concerned with the site only after I read it. So try not to worry about it until Monday.
For the last PPD I had, it was negative (no induration) but the redness lasted four weeks and was the size of a quarter. Then again, I can bruise if you look at me the wrong way.
wkate
6 Posts
Hello, I have a question about reactions to the PPD test. I received mine yesterday, and this morning when I looked at it, there is 12-13mm area of redness around the injection site which is very slightly raised. Around that area, there is a smaller, lighter 3-4mm boarder. Is this considered a positive reaction? I go on Monday to have the area read.