Subclinical TB is the reason for slow drop in TB incidence, says Soumya Swaminathan 

Subclinical TB is the reason for slow drop in TB incidence, says Soumya Swaminathan 

Subject: Sci

Sec: Health

Context:

TB infection can no longer be considered a binary — latent TB and active TB. People can also have TB disease and yet not display any of the characteristic symptoms associated with TB, such as cough. This is called subclinical TB. The national TB prevalence survey (2019-2021) found 42.6 % of the TB cases detected were subclinical and would have been missed if a chest X-ray was not included.

More on News:

• TB prevalence surveys done in high-burden countries in Asia and Africa have found a substantial proportion of subclinical TB, with the median being about 50%. Depending on how you define it and what symptom complex is used to define subclinical TB, the percentage varies from 30% to 80%. The high 80% is if you define subclinical TB as not having a persistent cough for more than two weeks.

Is there any high-burden country actively screening for subclinical TB cases as part of the TB programme?

• In Vietnam, there have been some very large-scale studies done across districts where they have screened the entire population, in what is called symptom agnostic screening.
• That means you do not worry whether people have symptoms or not, you go ahead and take an X-ray and collect a specimen for molecular testing.
• And there they found that by doing this annually for three years in that community, they were able to reduce TB prevalence by 50% compared with the control area.
• So it means that by going into the community and screening everybody and treating all the TB cases you find can bring down the burden of TB significantly in the community. There have been such demonstration studies, but I am not aware of any country that is doing it as part of the national TB programme.

What is Tuberculosis:

• Tuberculosis (TB) is an infectious airborne bacterial disease caused by Mycobacterium tuberculosis. .
• TB commonly affects the lungs (pulmonary TB) but can also affect other parts (extrapulmonary TB)
• Tuberculosis spreads from person to person through the air, when people who are infected with TB infection cough, sneeze or otherwise transmit respiratory fluids through the air.

What is Multidrug-Resistant TB (MDR-TB):

• In MDR-TB, the bacteria that cause TB develop resistance to antimicrobial drugs used to cure the disease.
• MDR-TB does not respond to at least isoniazid and rifampicin, the 2 most powerful anti-TB drugs.

Treatment options for MDR-TB are limited and expensive.

• CBNAAT (Cartridges Based Nucleic Acid Amplification Test) is used for early diagnosis of MDR-TB.