Tuberculosis, or TB, is a contagious bacterial infection that mainly affects the lungs, but may spread to other organs. Caused by the bacteria Mycobacterium tuberculosis, or M. tuberculosis, people can develop TB from breathing in tiny air droplets or particles from a cough or sneeze of an infected person. The QuantiFERON- TB Gold, or QFT-G, is the only blood test used to detect TB. NYC Health states QFT-G is an accurate, reliable and convenient diagnostic measure.
Inactive and Latent TB
A person who breaths TB bacteria into his lungs can either not become infected with TB, develop latent TB, develop active TB or develop active TB years after the initial infection. Some people exposed to TB can immediately destroy the germs and bacteria via their immune systems and clear it from their bodies. However, others develop latent TB where the germs settle in the lungs and begin to multiple. It takes the immune system several weeks to successfully block the bacteria in the lung walls, so it does not spread. The TB bacterium remains there for years but in a dormant state.
Active TB
In active TB, a person's immune system has failed, the TB bacterium has moved into the airways of her lungs, causing large air spaces, or cavities, to form. The air cavities contain oxygen, aiding the bacteria in survival. Eventually the bacterium may spread to the rest of the lungs as well to other parts of the body.
People with latent TB for years can develop active TB when the walled-off bacterium suddenly begins to multiply again. Although the exact cause as to what triggers reactivation remains unclear, researchers believe it occurs when the immune system becomes weakened. Reasons for a weakened immune system include drugs, alcohol, malnutrition and HIV/AIDS.
Symptoms
Most patients with latent TB remain asymptomatic, as they do not experience any symptoms. However, active TB can make people feel very sick. Active TB may cause cough, coughing up blood, excessive sweating, fatigue, fever, unintentional weight loss, breathing difficulty, chest pain and wheezing. Untreated, active TB that affects the lungs can eventually spread to other parts of the body through the bloodstream. TB can be fatal without proper treatment.
QuantiFERON- TB Gold
QuantiFERON- TB Gold, or QFT-G, was approved by the Food and Drug Administration in 2001, according to the U.S. Centers for Disease Control. The QFT-G is the only method to detect TB via a blood sample. The QFT-G diagnostically can find both active and latent TB. It's an indirect test for M. tuberculosis infection and measures a cell-mediated immune response to infected individuals. TB infected individuals are sensitized to M. tuberculosis proteins, and when the blood is incubated with M. tuberculosis, specific antigens, the T-lymphocytes, secrete interferon-gamma. The secretion of interferon-gamma results in a positive test for tuberculosis.
Treatment
Although the treatment regimens for latent and active tuberculosis are different, the prognosis for both is excellent if treatment is started quickly. People with latent TB commonly take isoniazid, either daily or twice a week for nine months, according to MayoClinic.com. The isoniazid medication regimen is a preventative measure to destroy the bacterium so latent TB doesn't become active TB in the future.
People diagnosed with active TB commonly take four medications--isoniazid, rifampin, ethambutol and pyrazinamide. The effects of these drugs are continuously monitored. In fact, during the first two weeks of therapy people are hospitalized until tests show they are no longer contagious. The four-drug treatment regimen may be stopped within two months depending on the severity of TB and whether the bacterium has completely been killed.
