Tuberculosis (TB) is the stuff of Victorian-era novels. Writers described artists and poets slowly wasting away from “consumption” in sanatoriums in the late 19th and early 20th centuries. Survival rates changed dramatically with the advent of antibiotics, but today TB is still one of the world’s deadliest diseases, according to the Centers for Disease Control and Prevention.
With a quarter of the world’s population infected with tuberculosis, a positive TB skin test is not uncommon. Here’s what you need to know about latent (not active) TB and treatment to stop you from developing an active disease.
What is TB and how is it spread?
TB is an infection caused by the bacteria Mycobacterium tuberculosis. TB mainly infects the lungs, although it can also affect any other organ. When someone with untreated active TB coughs or sneezes, the air is filled with droplets containing the bacteria. A person can be infected by inhaling these droplets.
Once someone is exposed to TB, three things can happen:
- They are infected and their immune system takes care of it and they do not test positive.
- They develop active TB with symptoms that include coughing, chest pain, coughing up blood, fatigue, night sweats, loss of appetite and weight loss.
- The infection gets into their lungs and their immune system contains it, causing latent, or “hidden or sleeping,” TB.
How is latent TB diagnosed?
TB is diagnosed by a positive reaction to a purified protein derivative (PPD) which is injected under the skin or by a QuantiFERON Gold blood test that can help detect TB. If you are positive, your doctor will do other testing such as a physical exam and chest X-rays to rule out active TB. If you do not have active TB, you are diagnosed with latent, or sleeping, TB.
What is latent TB?
“Latent TB is not an active infection, and you are not infectious, which means you cannot spread the disease,” said Louise Kane, MD, Lahey Hospital & Medical Center Pulmonary and Critical Care Medicine fellow. “It’s just sitting in the body doing nothing for the time being. However, there is always a chance it can be reactivated if a person has a secondary disease that makes their immune system less effective or they are on certain medications.”
Other factors that can come into play are a person’s general health, age, or if they have diabetes, chronic kidney disease, HIV, cancer, or on are immunosuppressant medications.
Should you get treatment for latent TB?
The answer depends on the patient. The risk of developing active TB after being diagnosed with latent TB is 5 percent for the first year and 5 percent for the second year. In most cases you should take medication.
“It’s mostly effective to clear any infection with no issues down the road,” Dr. Kane said. “You can’t predict the future. There may be a time when you need high-dose steroids, chemotherapy, or dialysis and if you didn’t get treated initially, now you may have to wait until after starting treatment for latent TB. It’s a commitment to taking antibiotics that may have side effects for a period of time. However, contracting active TB means more drugs for a longer period of time. It’s a risk/benefit analysis.”
How is latent TB treated?
Latent TB is generally treated by one of two antibiotic regimens: Isoniazid for nine months or Rifampin for four months. “We find there is better compliance with the shorter period. Rifampin does have some liver toxicity. One of the common side effects is that it turns all of your bodily fluids orange (tears, saliva, urine). It’s a bit disconcerting but has no lasting effects,” she said. “While on the antibiotics, you must avoid alcohol and use an alternative form of birth control if you are on oral contraceptives.”
After treatment ends for latent TB, your doctors will do a yearly screening to ask if you have experienced any symptoms, such as coughing, blood in phlegm, weight loss or fatigue. They may follow up with a chest X-ray if necessary. Those who have been treated are told to never have another PPD or TB blood test as in most cases they remain positive.
For more information on latent tuberculosis and other respiratory infections, speak with a Pulmonary and Critical Care Medicine provider.