What Are the Results of Tuberculosis?

The bacterium Mycobacterium tuberculosis is responsible for causing tuberculosis. Taking a TB test can help determine if you have active or latent TB. With active TB, your body has active TB that is progressively growing and multiplying within your body. Latent TB means that you have a TB infection, yet your immune system is capable of preventing TB bacterium from growing. There are two types of main tests to detect TB; the Mantoux skin test and blood tests. However, the Mantoux test is more commonly used.

Mantoux Skin Test

• A skin test uses small amounts of tuberculin that are injected into the top layer of your skin. Keep in mind that you cannot become infected from a TB test. According to the Centers for Disease Control and Prevention, it is important to see a health care provider 48 to 72 hours after receiving a skin test to detect the appearance of a hard, raised bump. If the bump is large, this can indicate a possible positive result.

Mantoux Results

• In most cases, a skin test can determine the presence of TB. However, the Mantoux test can result in false positives. According to the Mayo Clinic, if you are infected with a mycobacterium other than the bacteria that causes TB, you can create a false positive result. Being recently vaccinated with the Calmette-Guerin vaccine also can cause a false positive result. Even if you provide a positive result, your physician will have you undergo further testing, such as chest X-rays, CT scans and culture tests to provide an accurate diagnosis.

QuantiFERON Test

• According to the CDC, the use of QuantiFERON was approved by the FDA in 2005 to help diagnose the presence of TB. Blood samples are taken from you, and then mixed with synthetic tuberculin solutions. The mixture is then left to incubate for up to 24 hours. If you are infected with TB, the presence of interferon-gamma will be detected. Interferon-gamma are released by your white blood cells when your immune system responds to infections, viruses or bacterium introduced into your body.

Results of QuantiFERON

• In order for a QuantiFERON to be positive, you need to have a high presence of interferon-gamma. A positive result can be detected within one day. If interferon-gamma cannot be detected, the test will be determined as negative. However, errors can occur with a QuantiFERON test, such as misinterpretation of results. As with a skin test, further testing may be conducted to verify results.

Further Testing

• If a skin test or QuantiFERON test comes back positive, you will undergo an X-ray. A chest radiograph can detect abnormal lesions within your chest. A CT scan may be conducted when an X-ray produces abnormal spots upon your lungs. The CT scan can then provide a more detailed image of your lungs. A sputum smear also will be conducted to detect the presence of M. tuberculosis. With a sputum smear, you will be asked to cough and spit any material that is produced from the cough into a container. The mucus is then sent to a lab to be examined under a microscope.

Tuberculosis Symptoms

• Receiving a positive tuberculosis test doesn't necessarily mean that you're contagious. For example, a latent TB infection means that the tuberculosis bacterium is inactive and can't cause an infection in others. With latent TB, you also won't experience symptoms from the disease. According to the Mayo Clinic, having active TB is more serious, as you can transmit the disease to others with active TB. With active TB, you can experience symptoms of fatigue, fever and chills, weight loss, night sweats, coughing and chest pain.