FAQ – Patients

What is the scale of the tuberculosis (TB) problem?
How is TB spread?
What is TB infection (“LTBI” or “latent TB”)?
What is TB disease (“active TB”)?
Are certain individuals at an increased risk of progressing from latent TB infection to TB disease?
Are certain groups of individuals at an increased risk of exposure to Mycobacterium tuberculosis?
Is there a test for the detection of TB infection (“LTBI” or “latent TB”)?
Is there a test for the detection of TB disease (“active TB”)?
What is BCG (Bacille Calmette‑Guérin) vaccination?
What are the advantages of the T‑SPOT.TB test over a tuberculin skin test (TST)?
Is the T‑SPOT.TB test affected by previous BCG vaccination?
How quickly are T‑SPOT.TB test results available?
How important is treatment for TB disease?
Why is the treatment period for TB disease so long?
How important is treatment for TB infection (“LTBI” or “latent TB”)?
What happens if my test is positive?

What is the scale of the tuberculosis (TB) problem?
Although effective treatment has been available for over 70 years, tuberculosis (TB) remains the second leading cause of death from an infectious disease worldwide. The World Health Organization (WHO) estimates that more than onethird of the world’s population is infected with Mycobacterium tuberculosis. TB continues to be a significant disease due to factors such as immigration, the emergence of drugresistant TB strains, HIV, and other conditions that weaken the immune system.

Back To Top

How is TB spread?
Tuberculosis (TB) is passed from person to person through the air. Individuals with pulmonary (lung) TB can propel aerosols containing Mycobacterium tuberculosis complex organisms into the air when they cough, sneeze, sing, speak or spit. Persons who then inhale these aerosols can become infected.

Back To Top

What is TB infection (“LTBI” or “latent TB”)?
Individuals with TB infection (“LTBI” or “latent TB”) harbor dormant Mycobacterium tuberculosis complex organisms in their bodies but are not infectious and do not have symptoms of TB disease. TB infected individuals usually have a positive TSPOT.TB test result. It is estimated that 10% of immunocompetent persons with latent TB infection will develop TB disease during the course of their lives. The risk of progressing from TB infection to TB disease is increased in those with a weakened immune system.

Back To Top

What is TB disease (“active TB”)?
Tuberculosis disease, or active TB, develops when the immune system cannot prevent Mycobacterium tuberculosis complex organisms from multiplying in the body. After exposure, persons can develop latent TB infection or TB disease. TB disease most commonly occurs in the lungs (pulmonary TB). Symptoms of pulmonary TB disease may include fever, cough, night sweats, weight loss, and fatigue. Without treatment, TB mortality rates are high. Individuals with TB disease usually have a positive TSPOT.TB test result; however, assessing the probability of disease requires a combination of epidemiological, historical, medical and diagnostic findings.

Back To Top

Are certain individuals at an increased risk of progressing from latent TB infection to TB disease?

The risk of progression to tuberculosis (TB) disease is higher in certain individuals, including:

  • Persons with weakened immune systems
  • Children under the age of five
  • Persons living with HIV/AIDS
  • Organ or hematologic transplant recipients
  • Persons with radiographic evidence of prior healed TB
  • Those undergoing medical treatments with immunosuppressive agents such as systemic corticosteroids, TNFα antagonists and therapies following transplantation
  • Persons with leukemia or cancer of the lung, head or neck
  • Cigarette smokers
  • Drug or alcohol abusers
  • Persons with a low body weight
  • Persons with silicosis, diabetes mellitus and chronic renal failure/hemodialysis
  • Persons who underwent gastrectomy or jejunoileal bypass
  • Persons infected with TB within prior 2 years

Back To Top

Are certain groups of individuals at an increased risk of exposure to Mycobacterium tuberculosis?

Yes, certain groups are more likely to be exposed to Mycobacterium tuberculosis, which may lead to tuberculosis (TB) infection and/or disease. These include:

  • known close contacts of a person with infectious TB disease, primarily pulmonary TB
  • persons living in, immigrating from, or traveling to TBendemic regions of the world
  • persons who work or reside in facilities or settings with individuals who are at high risk for TB (e.g. hospitals, homeless shelters, correctional facilities, nursing homes, boarding schools, or residential facilities for persons living with HIV/AIDS)

Back To Top

Is there a test for the detection of TB infection (“LTBI” or “latent TB”)?
There are several methods to detect TB infection, broadly divided into tuberculin skin tests and blood tests. A tuberculin skin test (TST), which has been used to detect TB infection for over 100 years, requires an intradermal injection of a small amount of purified protein derivative (PPD) into the skin. In 4872 hours, the resultant induration is measured. More recently, blood based tests referred to as interferongamma release assays (IGRAs), such as the TSPOT.TB test, have been introduced.

Back To Top

Is there a test for the detection of TB disease (“active TB”)?
Identification of individuals with active TB disease is critical to TB control. Those suspected of having TB disease may undergo a number of tests to confirm the diagnosis. The TSPOT.TB test may be used as a diagnostic aid in patients suspected of having TB disease when used in conjunction with radiography and other medical and diagnostic evaluations.

Back To Top

What is BCG (Bacille CalmetteGuérin) vaccination?
Bacille CalmetteGuérin (BCG) vaccine is used in many countries with a high prevalence of TB to prevent childhood tuberculous meningitis and miliary disease, but confers limited protective value in adults. The BCG vaccine is also used as an immunotherapeutic agent for individuals with bladder cancer. BCGvaccinated individuals may produce a positive tuberculin skin test (TST), even if they are not infected with Mycobacterium tuberculosis complex organisms. This is a common cause of TST inaccuracy.

Back To Top

What are the advantages of the TSPOT.TB test over a tuberculin skin test (TST)?

The TSPOT.TB test has a number of advantages over a tuberculin skin test (TST), including:

  • Single visit to complete test (versus 2 4 with TST)
  • Improved sensitivity (reliable in patients with weakened immune systems)
  • Improved specificity (not affected by BCG vaccine and most nontuberculous mycobacteria)

Back To Top

Is the TSPOT.TB test affected by previous BCG vaccination?
No, unlike a tuberculin skin test, the TSPOT.TB test does not produce a falsepositive result due to BCG vaccination.

Back To Top

How quickly are TSPOT.TB test results available?
Laboratory processing of the TSPOT.TB test can be completed in approximately 24 hours. Most laboratories typically report results within 36 48 hours of sample receipt.

Back To Top

How important is treatment for TB disease?
Treatment for tuberculosis (TB) disease is vital. The goals of treatment include not only curing the patient, but reducing transmission to others. In general, the duration of treatment is 6 – 9 months, but is much longer in those with drugresistant TB. It is crucial that individuals with TB complete their entire course of treatment even if their symptoms improve. TB that is not adequately treated can reactivate or become resistant to drugs, making it more difficult to treat.

Back To Top

Why is the treatment period for TB disease so long?
Most antibiotics capable of destroying bacteria can only do so while the bacteria are actively replicating. The replication cycle of Mycobacterium tuberculosis complex organisms is relatively long; therefore, lengthy treatment is required to ensure that all of the bacteria are destroyed. If the treatment is inconsistent or too short, some bacteria may survive, potentially allowing tuberculosis (TB) disease to reactivate or develop drugresistance.

Back To Top

How important is treatment for TB infection (“LTBI” or “latent TB”)?
As long as TB mycobacteria are in the body, there is a risk of progressing to TB disease. Completed treatment regimens reduce this risk by up to 90%.

Back To Top

What happens if my test is positive?

Your healthcare provider will determine the next steps, which may include evaluating if any additional testing, such as a chest xray, is needed. Your provider may also evaluate whether treatment is indicated. A positive test means you may have either latent TB infection or active TB disease.*

*Information provided is not intended as a substitute for medical diagnosis by a trained healthcare provider. You should always consult your healthcare provider about any healthcare questions you may have.

Back To Top