What causes Tuberculosis?
Tuberculosis (TB) is a notifiable disease caused by the bacteria Mycobacterium tuberculosis and uncommonly by Non tuberculous mycobacteria. It most commonly affects the lungs although it can also affect the lymph nodes, brain, heart, skin, kidneys, bones etc. TB can be fatal if not recognized and treated. However, TB is treatable and preventable.
TB kills an estimated 480,000 Indians every year and more than 1400 every day. TB in India has 4 fold higher prevalence in those with a low standard of living index compared to those with a high standard of living index. Prevalence of TB is three times higher among ever-smokers as compared to that of never smokers.
How does tuberculosis occur?
The tuberculosis (TB) bacteria are spread through the air from a person who is ill with active TB that involves the lungs or airways. In some cases, the person develops an immune response that controls the bacteria by containing it inside the body. The person does not develop active TB at this time but is said to have latent TB infection (LTBI). During this latent stage, person is well and cannot spread the infection to others. Active TB (TB disease) may develop if latent infection is not fully treated or gets reactivated. This is called reactivation TB, and it occurs in 5 to 10 percent of people with latent infection at a later time in their lives. Reactivation can also occur more readily in people with HIV, diabetes mellitus, malnutrition, or those who take medications that weaken the immune system, such as medications for rheumatoid arthritis, steroids, or cancer chemotherapy.
How is latent tuberculosis diagnosed?
Latent tuberculosis (TB) infection (LTBI) can be diagnosed with a skin test (tuberculin skin test/ Mantoux test) or with a blood test (interferon-gamma release assays -IGRAs), followed by a clinical evaluation and imaging (usually a chest X-ray) to make sure the tuberculosis is not active and not causing disease.
What are the symptoms of active TB?
Signs and symptoms of active TB include:
Coughing that lasts for two or more weeks
Coughing up blood
Chest pain, or pain with breathing or coughing
Unintentional weight loss
Loss of appetite
When TB occurs outside your lungs, signs and symptoms vary according to the organs involved. For example, tuberculosis of the spine may cause back pain, and tuberculosis in kidneys might cause blood in urine
Micronutrient deficiency esp. iron and folate, vitamin A, zinc, vitamin D
How is Active Tuberculosis Diagnosed?
It is very difficult to diagnose TB by a person’s symptoms on their own as some other diseases have same symptoms. Clinical diagnosis often includes chest X-ray, ultrasound/CT/MRI of site involved.
A diagnosis is usually only certain when there is definite evidence of TB bacteria which includes sputum/specimen microscopy, the culture test as well as the new GeneXpert/ CBNAAT test/LPA.
Treatment of latent tuberculosis
Treating LTBI greatly reduces the risk of the infection progressing to active TB later in life. India has 40% of the population infected with Mycobacterium Tuberculosis. Treating 40% of the population for LTBI based on Tuberculin Skin Test (TST) positivity or Interferon Gamma Release Assay is neither rational nor practicable. So, LTBI treatment is given to high-risk infected patients such as those receiving long term corticosteroids, immunosuppressants, HIV infected, children less than 6 years of age, high risk adult and patients with silicosis.
Treatment of active tuberculosis
If there is evidence of active lung TB on a chest X-ray, sputum microscopy, cultures and GeneXpert are performed. Other tests, such as a bronchoscopy or biopsy may also be needed. A tissue biopsy/FNAC/Aspiration may be performed to obtain specimens for culture if TB is suspected in other organs (such as lymph nodes, pleural fluid or kidney).
While waiting for the results of the culture/GeneXpert, treatment with several (usually four) TB drugs may be recommended. Infection caused by a strain of TB that has become resistant to standard TB drugs (MDR/XDR TB) is more difficult to treat and may require five or more medications and a longer duration of treatment.
Treatment of TB should be taken in adequate doses and for total duration otherwise it may lead to drug resistant TB.
- DR GURMEET SINGH CHABBRA
Sr. Consultant Respiratory & Sleep Medicine
OPD Timings : Mon-Sat 10, 10 AM-5PM
QRG Health City, Sector 16, Faridabad