Latent Tuberculosis or Tuberculosis disease: What is the difference?

Tuberculosis or TB is caused by a bacteria called mycobacterium tuberculosis. As tuberculosis (TB) in India is endemic many people breathe in the TB bacteria and a lot of them would get infected. In most of these infected people the body is able to stop the bacteria from growing and turning into active tuberculosis disease. This means that the tuberculosis bacteria can live inside the human body, adult or child without making him or her sick or feeling unwell. This form of tuberculosis is called Latent Tuberculosis, also called latent tuberculosis infection (LTBI).

Now, when an adult or child develops symptoms such as fever, cough, blood in sputum, reduced appetite, weight loss, enlarged lymph nodes, etc, this condition is termed as active tuberculosis (TB) or TB disease.

Can a child with latent tuberculosis progress into active tuberculosis disease?
The chances of progressing from latent tuberculosis (TB) into active tuberculosis (TB) disease is highest in infants less than one year of age, almost to the tune of 50%. In children between 1-5 years of age, the chances could be somewhere like 20%. Thereafter till the age of 18 years of age the chances of converting from a latent tuberculosis into an active TB disease is thought to be around 10%. The risk remains almost similar in adulthood as well.

How do we diagnose latent tuberculosis (TB)?
There are two ways to diagnose a latent tuberculosis (TB) infection in children or adults. Tuberculin skin test also called as a Mantoux test can be used. The other way to diagnose a latent tuberculosis (TB) infection is a blood test, which is also termed as Quantiferon TB gold.

Does chest X-ray show latent tuberculosis (TB)?
Children or adults who have latent tuberculosis have normal xray chest. Chest x ray abnormalities appear only if the child or the adult has active tuberculosis (TB).

What are the conditions where the chances of progressing from latent tuberculosis into active tuberculosis disease is higher?
There are conditions when the chances of progressing from latent tuberculosis (TB) into active tuberculosis (TB) disease is higher. These conditions could be children having immunosuppressed conditions such as nephrotic syndrome, children on cancer chemotherapy, children getting any drugs for medicines which can reduce their immunity levels, etc.

Do all children and adults with latent tuberculosis require treatment?
All children and adults having latent tuberculosis (TB) are not given treatment in India. This is because the chances of re-infection are extremely high.

When do we recommend treatment for latent tuberculosis in children or adults?
Treatment for latent tuberculosis is recommended for household close contacts with an adult or adolescent in the family with active tuberculosis (TB) disease in the chest. In addition children who are due to start on some form of immunosuppressive therapy and have an investigation suggestive of latent tuberculosis (TB) disease are also offered treatment for latent TB.

What is the treatment required for latent tuberculosis in children?
As per the recent guidelines from the Ministry of Health and Family Welfare, Government of India and the World Health Organization latent tuberculosis (TB) is treated with Isoniazid. The duration of treatment with isoniazid is 6 months. Isoniazid is a very safe medicine and does not have any significant side effects.

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