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. Recently, the Tamil Nadu TB prevalence survey found 39% subclinical TB cases.
Dr. Soumya Swaminathan , the Principal Adviser at the Health Ministry for the National Tuberculosis Elimination Programme (NTEP), talks about the various challenges in detecting subclinical TB cases and ensuring that such people begin and complete the treatment. Considering that both the national and the Tamil Nadu TB prevalence surveys have found the prevalence of subclinical TB to be high, can it be assumed that subclinical TB prevalence will be high in all high-burden States in India? Yes.
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.
What we are learning now from the meta-analysis of prevalence surveys done across high-burden countries is that there is a significant bur.