Published on LMS

Presumptive TB case refers to a patient who presents with symptoms or signs suggestive of TB disease (previously known as a TB suspect) and where further diagnostic workup including bacteriological investigation is required.

 Presumptive TB can be categorized into

1. Presumptive Pulmonary TB (P TB) - Symptoms are directly related to lungs (Cough, hemoptysis)

2. Presumptive Extra Pulmonary TB (EP TB) - Symptoms/ signs are specific to an extra pulmonary site (example: Lymph node swelling)

NTEP laboratory network is comprising of National Reference Laboratories (NRLs), state level Intermediate reference laboratories (IRLs), Culture & Drug Susceptibility Testing (C & DST) laboratories and peripheral level laboratories. Peripheral level laboratories consist of  designated microscopy centres (DMCs) and NAAT labs.

NTEP has a quality assured laboratory network for bacteriological examination of sputum in a 3-tiered system.

Culture Drug Susceptibility Testing (CDST) is a growth-based phenotypic method used to check the susceptibility of Mycobacterium tuberculosis strains to various first and second line anti-TB drugs. Mycobacterial resistance to a particular drug is identified if there is growth observed in culture in presence of that drug.

Culturing TB Bacilli is well known and historic method for detection/ confirmation of Tuberculosis. It is a highly sensitive and specific phenotypic test; it can detect even a few viable bacilli in the sample (Upto 10 Colony Forming Units- CFUs). TB bacilli multiply in the culture and form colonies of TB bacilli which can are easily be identified.

Based on the growth media used Culture is divided in to two types, Solid and Liquid Culture methods. Types Culture:

As per the Integrated Drug Resistant Tuberculosis (DR-TB) Diagnostic Algorithm:

First Line (FL) LPA

• Performed using GenoType MTBDR plus ver 2.0 kit
• GenoType MTBDR plus (Figure) identifies:
  • Mutations in the Rif-resistance Determining Region (RRDR) of rpoB gene (from codon 505 to 533) to detect Rifampicin resistance
  • Mutations in the inhA promoter (from -16 to -8 nucleotides upstream) and the katG (codon 315) regions to identify Isoniazid resistance.

The tests are performed using Trueprep AUTO Sample Pre-treatment and Prep kits and Truenat micro-PCR chips.

To detect M. tuberculosis, the Truenat MTB chip amplifies a portion of the ribonucleoside-diphosphate reductase gene, nrdB with a Limit of Detection (LOD) of about 100 Colony Forming Units (CFU)/ml sputum sample.

DNA extraction and detection of M. tuberculosis takes approximately one hour.

Screening technology in NTEP: 

Nikshay is an Integrated ICT system for TB patient management and care in India. Nikshay was launched in 2012 and since then, various improvements have been made in the system.

Nikshay provides-

Screening for active tuberculosis (TB) a process to filter out people who are less likely to have TB, from a group. Screened positive people are likely to have TB and are confirmed subsequently using a TB diagnostic test. This will allow finite diagnostic testing resources to be used on the remaining.