What Happens When Your Tuberculosis Skin Test Is Positive?

When I was hired as a nurse aide at a local hospital, I was required to get a PPD or tuberculosis skin test. When the results were read, it turned out I had a positive reaction. Having completed three semesters of nursing school, I knew not to panic just yet. But if you're not a health care professional or even student like I was, this could be scary. This article will explain what happens when your tuberculosis skin test is positive and what to expect next.

What does the tuberculosis skin test consist of?

A tuberculosis skin test is used to determine exposure to tuberculosis. It is a two-step process. Your health care provider will inject a small amount of TB protein serum into your inner forearm. You will see a bump form where the serum was injected. 48-72 hours later, your health care provider will look at the injection site to see if there is any reaction. The test must be repeated the following week as part of the two-step process.

How can I tell if there is a reaction?

Your health care provider is not looking so much as he is feeling for a reaction. If you still have a bump or whealing at the injection site 2-3 days later, he will need to measure it. For most healthy, low-risk people, anything 15mm or above in diameter is considered a positive or reactive tuberculosis skin test. But for some moderate risk people, like health care professionals, a reading above 10mm is positive and my reading was 11mm.

Does a positive tuberculosis skin test reading mean I have TB?

No! It only means you may have been exposed to TB and you may have some bacteria (mycobacterium tuberculosis) lying dormant in your body. It does not guarantee you have an active case of TB. This condition is known as latent tuberculosis and shows no outward signs or symptoms and is not contagious. You need further testing for a more definitive diagnosis.

What further testing?

A positive tuberculosis skin test reading requires a chest x-ray for diagnosis. You need to remove your shirt and inhale while the x-rays are being taken. Because TB is a reportable communicable disease, you should get the results of your x-ray ASAP. Mine took only about 10 minutes from procedure to diagnosis. My x-rays showed I was negative for TB. A positive result would have lead to a diagnosis of active tuberculosis and required medication treatment for around 9 months.

Will I still need treatment if the x-ray comes back negative for TB?

Your doctor will likely require you take medications as a precaution to kill any TB bacteria that may be in your body. Isoniazid is the drug of choice for treating latent TB and that's what I am taking for the next 6-9 months. One potential side effect of Isoniazid is liver damage. So any signs like yellowing of the eyes or nausea/vomiting need to be reported to my health care provider immediately. Because I have no history of liver problems or drug and alcohol abuse, the chances of me developing liver damage are very slim, but I still need to be alert. And my future TB screenings will consist of chest x-ray only and not the skin test.

Sources:

CDC website, Tuberculosis, last update January 2012

US National Library of Medicine PubMed Health, Isoniazid, last revision October 2010

Personal experience