PPD Skin Test

ppd test procedure

On image: ppd test procedure

TB is a highly contagious disease. The World Health Organization (WHO) estimates that TB is 2nd only to HIV and AIDS as the greatest international killer. Nevertheless, the disease is fairly uncommon in the United States. The majority of people in the United States infected with TB do not show symptoms. You must get a PPD skin test if you work in the healthcare field. All healthcare employees should be routinely evaluated for TB.

What Is PPD Test?

A purified protein derivative (PPD) skin test is a test that identifies if you have tuberculosis (TB).

TB is a major infection, typically of the lungs, brought on by the bacteria Mycobacterium tuberculosis. This bacteria spreads when you take in the air breathed out by a person infected with TB. The bacteria can remain non-active in your body for several years.

When your body immune system ends up being weakened, TB can end up being active and produce symptoms such as:

  • fever
  • weight reduction
  • coughing
  • night sweats

If TB does not react to antibiotics, it’s referred to as drug-resistant TB. This is a serious public health problem in many areas of the world, consisting of Southeast Asia and Africa.

When TB contaminates your body, it becomes extra sensitive to specific aspects of the bacteria, such as the purified protein derivative. A PPD test checks your body’s existing sensitivity. This will inform medical professionals whether or not you have TB.

How PPD Skin Test is Performed?

How to do a PPD test? You will need 2 check outs to your doctor’s workplace for this test.

At the first see, the healthcare supplier will clean an area of your skin, generally the inside of your forearm. You will get a small shot (injection) that contains PPD. The needle is carefully put under the top layer of skin, triggering a bump (welt) to form. This bump typically disappears in a couple of hours as the product is absorbed.

After 48 to 72 hours, you should go back to your company’s office. Your company will inspect the area to see if you have had a strong response to the test.

Do I need to Be Prepared for PPD Test?

There is no special preparation for this test.

Inform your provider if you have ever had a favorable PPD skin test. If so, you need to not have a repeat PPD test, except under uncommon situations.

Inform your supplier if you have a medical condition or if you take certain medicines, such as steroids, which can affect your immune system. These situations might result in unreliable test outcomes.

Tell your company if you have actually gotten the BCG vaccine and if so, when you received it. (This vaccine is just given beyond the United States).

How the Test will Feel

You will feel a brief sting as the needle is placed just below the skin surface.

Why Is PPD Skin Test Performed?

This test is done to discover if you have actually ever come in contact with the bacteria that causes TB.

TB is an easily spread out (contagious) disease. It most often affects the lungs. The bacteria can stay inactive (dormant) in the lungs for many years. This situation is called hidden TB.

Most people in the United States who are infected with the bacteria do not have signs or symptoms of active TB.

You are more than likely to need this test if you:

  • May have been around somebody with TB
  • Operate in healthcare
  • Have a weakened body immune system, due to certain medications or disease (such as cancer or HIV and AIDS).

How to Read a PPD Test

“Reading” the skin test for TB indicates detecting a raised, thickened area of skin reaction, referred to as induration. Induration is the key product to discover, not inflammation or bruising. Skin tests need to be read 48-72 hours after the injection when the size of the induration is maximal. Tests checked out after 72 hours tend to ignore the size of the induration and are not accurate.

Negative PPD Test Results

A negative reaction normally implies you have actually never ever been infected with the bacteria that cause TB.

With an unfavorable reaction, the skin where you received the PPD test is not swollen, or the swelling is really small. This measurement is various for children, people with HIV, and other high-risk groups.

The PPD skin test is not an ideal screening test. A couple of people infected with the bacteria that cause TB might not have a response. Likewise, illness or medications that damage the body immune system may cause a false-negative outcome.

negative ppd test

Picture of negative PPD skin test – what does a negative PPD test look like

Positive PPD Test Results

An irregular (positive) result methods you have been infected with the bacteria that cause TB. You may need treatment to lower the risk of the disease coming back (reactivation of the disease). A positive skin test does not indicate that an individual has active TB. More tests should be done to inspect whether there is active disease.

A small reaction (5 mm of firm swelling at the site) is considered to be favorable in people:

  • Who have HIV.
  • Who have gotten an organ transplant.
  • Who have actually a reduced body immune system or are taking steroid therapy (about 15 mg of prednisone each day for 1 month).
  • Who have been in close contact with a person who has active TB.
  • Who have modifications on a chest x-ray that look like previous TB.

Bigger responses (bigger than or equal to 10 mm) are thought about favorable in:

  • People with a known unfavorable test in the past 2 years.
  • People with diabetes, kidney failure, or other conditions that increase their chance of getting active TB.
  • Health care employees.
  • Injection drug users.
  • Immigrants who have actually moved from a nation with a high TB rate in the previous 5 years.
  • Children under age 4.
  • Infants, children, or adolescents who are exposed to high-risk adults.
  • Students and employees of certain group living settings, such as prisons, nursing houses, and homeless shelters.
Positive PPD skin test for TB

Picture of positive PPD skin test – what does a positive PPD test look like

In people without any recognized risks of TB, 15 mm or more of firm swelling at the site indicates a positive reaction.

People who were born outside the United States who have had a vaccine called BCG might have a false-positive test result.

Risks Associated with PPD Test

There is an extremely little risk of severe soreness and swelling of the arm in people who have actually had a previous positive PPD test and who have the test once again. This response can also occur in a couple of people who have actually not been evaluated before.

Alternative names of PPD test: Purified protein derivative standard; TB skin test; Tuberculin skin test; Mantoux test.


Last modified: October 17, 2017

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