TB Tests

What is a TB/PPD Skin Test?

A TB skin test is a small intradermal injection placed under the skin of the forearm.  When placed correctly, the injection should produce a pale elevation of the skin (a wheal) 6 to 10 mm in diameter.   

The test is then read between 48 and 72 hrs. after being placed. The reaction should be measured in millimeters of the induration (palpable, raised, hardened area or swelling).  


Some employers require 2 step PPD testing .  Two-step testing is useful for the initial skin testing of adults who are going to be retested periodically, such as health care workers or nursing home residents. This two-step approach can reduce the likelihood that a boosted reaction to a subsequent TST will be misinterpreted as a recent infection.  

After the 1st step is read the 2nd step is administered 1- 3 weeks later (i.e. the second test can be placed 7-21 days after the first). If the second test is negative, the person is considered uninfected. If the second test is positive, then the person is considered to have a “boosted” reaction to an infection that occurred in the past. Beyond that, secondary testing is useful to help offset potential false negative testing results .

We provide TB skin tests on Monday's, Tuesday's & Wednesday's, no appointment necessary.


What can I do with my arm?

Anything you would regularly do.

How do I clean my arm?

You can take showers and baths as you normally do.

What do I do if my arm itches or blisters?

Put an ice cube in a washcloth and place it on your arm. DO NOT SCRATCH!

Can I use a band-aid if it bleeds?

No.  Band-aids increase allergies.  Use a dry cotton ball to dab away any blood.