The two-step tuberculin skin test is being done to check if the new employee has been exposed to tuberculosis (TB) in the past. TB is a bacterial infection that primarily affects the lungs and can be spread through the air when an infected person coughs or sneezes. The two-step test is necessary to ensure that any reaction to the test is not due to a previous TB infection, which can cause a false positive result.
The procedure for the two-step tuberculin skin test involves two separate injections of a small amount of purified protein derivative (PPD) under the top layer of the skin on the forearm. The first injection is given and the area is marked. After 48-72 hours, the healthcare provider will examine the area for any swelling or redness, which is an indication of a reaction to the test. If the reaction is negative, indicating that the person has not been exposed to TB in the past, a second injection will be given at least one week later. The second injection is necessary to ensure that a delayed hypersensitivity reaction does not occur, which can also cause a false positive result.
The new co-worker should be informed that the test is a standard procedure to check for a past TB infection, and that it involves two separate injections and two follow-up visits to read the results. They should also be instructed to keep the area dry and avoid rubbing or scratching the injection site, as this can affect the accuracy of the test. If the test does show a positive reaction, the new employee will need further evaluation and possibly treatment for TB to prevent the spread of the infection to others.