Principles of TB Diagnosis under NTEP

The National TB Elimination Program (NTEP), promotes the following principles to diagnose TB:

1. Try to establish the microbiological confirmation for all cases
2. Use rapid molecular diagnostics upfront wherever possible for diagnosis of TB and early identification of resistance to treating drugs.
3. Focus more on quality sample collection and timely transportation for a better microbiological confirmation 

Microbiological Confirmation for All Cases

Microbiologically confirmed TB refers to a presumptive TB case from whom a biological specimen is positive for acid fast bacilli smear microscopy, or positive for Mycobacterium tuberculosis on culture, or positive for TB through Rapid Diagnostic molecular tests - Nucleic Acid Amplification Test (NAAT) and Line Probe Assay (LPA). Establishing microbiological confirmation is key for all TB cases. Clinically diagnosing TB should be limited only to very few patients where, in-spite of high suspicion, microbiological confirmation could not be established, even after all possible efforts. The entire diagnostic algorithm puts utmost efforts to establish the microbiological evidence in a case of TB.

Upfront Rapid Molecular Diagnostics

Knowing the drug resistance pattern at the earliest is key for success of the treatment. Hence, the current policy highlights the importance of using molecular diagnostic test upfront wherever possible.

Complete diagnosis of TB is achieved by:

• Offering NAAT (CBNAAT/ Truenat) to all notified new patients and to test for resistance to Rifampicin. This is termed as Universal Drug Sensitivity Test (DST) for Rifampicin. Efforts are being made to collect specimen from all TB patients for NAAT at baseline.
• Testing individuals belonging to key population groups (clinically, socially vulnerable), those with extra pulmonary TB, people living with HIV and paediatric patients (after X-ray screening). They are directly referred for TB testing by NAAT
• For upfront NAAT, one specimen is tested using NAAT and if TB is detected, the other sample is used for further cascade testing by LPA and liquid culture

Quality Sample Collection and Transport

For TB diagnosis, it is essential that a good sputum sample is collected. A good specimen consists of recently discharged material from the bronchial tree with minimum amount of oral or nasopharyngeal material, presence of mucoid or mucopurulent material and should be 2-5 ml in volume. The specimen is collected in a sterile container after rinsing of the oral cavity with clean water. The collected specimens should be packaged and transported to the laboratory as soon as possible after collection.

Resources

• Guidelines for Programmatic Management of Tuberculosis Preventive Treatment, Central TB Division, MoHFW 2021
• Training Modules for Programme Managers and Medical Officers,Central TB Division, MoHFW 2020
• Guidelines on Airborne Infection Control, Directorate General of Health Services, MoHFW 2010

Assessment