CDST_LT: Diagnostic network and hierarchy in NTEP

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.

Figure: Laboratory network of NTEP

Resources:

• TB India Report 2021

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The National Reference Laboratories (NRLs) constitute the third tier of the National Tuberculosis Elimination Programme (NTEP) laboratory network hierarchy. 

They provide quality assurance and certification services for the Culture and Drug Susceptibility Testing (C&DST) labs and coordinate with the World Health Organisation (WHO) Supranational Reference Laboratory (SNRL) network.

There are six designated NRLs which are delineated in the figure below.

Image

Figure: Six National Reference Laboratories under NTEP in India

NIRT, Chennai, in addition to being one of the NRLs is also one of the WHO designated SNRLs for the Southeast Asia Region.

Resources

• Guidelines for Programmatic Management of Drug-resistant TB in India, 2021.
• NTEP Laboratory Network: Overview.

• National Reference Laboratories (NRLs) conducts annual on-site evaluation/supervisory visits to laboratories for assessing the quality of microscopy, culture and drug susceptibility test (C&DST), and for improvement of the overall laboratory quality. 
• NRLs also assist Central TB Division (CTD), in developing laboratory guidelines, standard operating procedures (SOPs), and conduct training to state-level Intermediate reference laboratories (IRLs) and other technical issues.
• NRLs conduct C&DST training to the IRLs, and develop SOPs for the technical procedures, equipment maintenance, infection control and recording and reporting. 
• NRLs are also responsible for offering second-line drug susceptibility tests (DST) for multi-drug resistant TB (MDR-TB) treatment failures. 
• NRLs are responsible for the accreditation of the mycobacteriology laboratory for culture and drug sensitivity testing under the National Tuberculosis Elimination Program (NTEP).
• In addition, NRLs are also responsible for the conduct of research for the programme and evaluation of newer tools for the diagnosis of TB.
• The National Institute for Research in Tuberculosis (NIRT) Chennai, the Supranational Reference Laboratory (SRL) of the region is responsible for the external quality assurance of the other 5 NRLs. NIRT is in turn quality-assured through the SRL coordinating laboratory at Antwerp, Belgium. 

Assessment Questions

Some Culture and Drug Susceptibility Test (C&DST) laboratories host an Intermediate Reference Laboratory (IRL) under the National TB Elimination Programme (NTEP). 

There is at least one IRL per state at an identified location, usually in a secondary or tertiary level public health facility. There are 34 IRLs in India.

The IRLs are responsible for:

• Undertaking training on laboratory technologies for district and field level staffs
• Conducting on-site evaluation visits to districts for sputum microscopy at least once a year
• Undertaking panel testing of Senior TB Laboratory Supervisors (STLS) at each district linked to it
• Ensuring the proficiency of staff performing National Tuberculosis Elimination Programme (NTEP) smear microscopy activities by providing training to laboratory technicians and STLS

Resources

• Guidelines for Programmatic Management of Drug-resistant TB in India, 2021.
• NTEP Laboratory Network: Overview.

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Under the National Tuberculosis Elimination Programme (NTEP), many labs are established at the regional level within states for providing Culture and Drug Susceptibility Testing (C&DST) facilities for presumptive TB/DRTB and for TB/DRTB patients. C&DST laboratories are mostly located in intermediate reference laboratories (IRLs) or medical colleges. There are 42 C&DST laboratories established under the programme in different geographies. Dedicated human resources are provided for the laboratories under the programme. Districts are linked with laboratories for providing facilities for Culture and DST using: Phenotypic Methods (Solid – Lowenstein Jensen (LJ), and Liquid Culture – Mycobacteria Growth Indicator Tube (MGIT)) Genotypic technology (Line Probe Assay (LPA) and Cartridge Based Nucleic Acid Amplification Test (CBNAAT))

Figure: Culture and Drug Susceptibility Testing (C&DST) facility, Source: The Foundation For Innovative New Diagnostics (FIND)

Resources

• Guidelines for Programmatic Management of Drug Resistant TB in India, 2021
• Training Modules (1-4) for Programme Managers and Medical Officers; New Delhi, India: Central TB Division, July 2020

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The National Tuberculosis (TB) Elimination Program (NTEP) has a network of Nucleic Acid Amplification Tests (NAAT) laboratories coupled with Designated Microscopy Centers (DMCs) to form the backbone of the diagnostic component of TB services.

Nucleic Acid Amplification Tests (NAAT) laboratories includes Cartridge-based NAAT (CBNAAT) and TrueNat tests. These tests detect tuberculosis as well as rifampicin resistance and are more sensitive than smear microscopy.

Functions of Nucleic Acid Amplification Test (NAAT) Laboratories:

1. Acting as a hub for collection of samples from public and private health facilities (spokes)
2. Universal Drug Susceptibility Testing (UDST) to rule out rifampicin resistance among confirmed TB patients
3. Timely provision of NAAT test result to the TB patient, medical officer of the concerned health facility and NTEP staff for related actions
4. Acting as a sample dispatch center for the Culture DST laboratory for subsequent processing of samples for first-line line probe assay (LPA) and second-line drug resistance testing utilizing second line LPA and liquid culture DST
5. Recording and reporting including digitization of diagnostic process from collection to test result in NTEP Nikshay portal and Laboratory Information Management System
6. Management of supplies and logistic associated with laboratory logistic (CBNAAT cartridges and TrueNAT chips) and reporting any additional requirement thereof
7. Supporting the quality assurance activities undertaken by District or Intermediate Reference Laboratory under NTEP
8. Support health system in carrying out special drives for vulnerable and at-risk population and their testing directly by CBNAAT (slum population, diabetic population, smoker, malnourished people, patients of silicosis and kidney dialysis etc.)

Resources

• RNTCP Technical and Operational Guidelines for TB Control in India, 2016.
• Guidelines for Programmatic Management of Drug Resistant Tuberculosis in India, 2021.

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Sputum microscopy diagnostic services under the National TB Elimination Programme (NTEP) are provided by the Designated Microscopy Centres (DMCs) established at the Peripheral Health Institution (PHI) level, where a functional binocular microscope and a trained Laboratory Technician (LT) is available. Light Emission Diode Fluorescent microscopes are provided to high-load PHI-DMCs such as that of the medical colleges. 

Based on latest directives, a DMCs may be established at all PHIs (Public and Private) of the country as needed. It is mandatory to have a DMC at all medical colleges in the country.

As molecular technologies like Truenat are also used in DMCs, NTEP has planned to rename DMCs as TB Diagnosis Centres (TDCs).

Criteria to be a DMC

The DMCs should satisfy the following criteria:

1. NTEP-trained Laboratory Technician (LT) should be present.
2. A functional binocular microscope should be present in the laboratory.
3. Physical infrastructure in the laboratory should meet NTEP guidelines.
4. Daily new adult outpatient cases of at least 60-100 and/or workload of at least 3-5 sputum smears per day for the LT in the laboratory.

DMCs in the public sector, at the onset of the programme, are provided with funds to undertake minor civil works to build up their physical infrastructure and are provided with binocular microscopes.

Human Resources Norms

• For the purpose of NTEP, a PHI is a health facility which is manned by at least a Medical Officer (MO).
• In addition to the MO and LT, there is 1 TB Health Visitor (TBHV) per one lakh urban population to support the urban TB control activities.

Other Criteria

Microscopy Centres may be established beyond population norms in medical colleges, corporate hospitals, Employee State Insurance Corporation (ESIC), railways, Non-government organisations (NGOs), private hospitals, Ayushman Bharat - Health and Wellness Centres (AB-HWCs), etc.

Before designating a DMC in other sectors, there should be a formal agreement by the hospital/ laboratory to take part in the External Quality Assurance (EQA) and to allow the concerned NTEP staff to supervise as per the NTEP guidelines.

If the above criteria are met by any private laboratory, the lab is considered for establishing a DMC.

• To provide better access for diagnosis of TB, all PHIs, wherever LTs and binocular microscopes are available, can be upgraded to a DMC irrespective of the population norms or OPD attendance.
• All DMCs should comply with the Quality Assurance (QA) mechanisms as per the EQA guidelines.

Resources

• NTEP Training Modules 1-4 for Programme Managers & Medical Officers, 2020.
• Operational Guidelines for TB Services at Ayushman Bharat Health and Wellness Centres.

Assessment Questions

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Functions and Integrated Services of the DMC

• Testing of Sputum samples by Microscopy.
• Request/ referral for microscopy or Nucleic Acid Amplification Test (NAAT) or Culture and Drug Susceptibility Test (C&DST) or Chest X-ray (CXR) or Tuberculin Skin Test (TST) is generated at the PHI-DMC, as well as follow-up tests.
• Maintain consumables and logistics required for testing/ packaging and transport.
• Maintain TB laboratory registers for recording and reporting.
• Notify every TB patient in Nikshay at the earliest and update information of patients on comorbidity, treatment adherence, treatment outcome, contact investigation and TB Preventive Treatment (TPT).
• Biomedical waste management for the waste generated at DMCs.
• A DMC is required to participate in the External Quality Assurance system(EQA) of NTEP to ensure standardized quality diagnostic testing. 

Resources

• NTEP Training Modules 1-4 for Programme Managers & Medical Officers, 2020

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To increase access to diagnostic services, NTEP has a provision for sputum collection centres in areas where the health facility is not equipped with key requirements to conduct sputum microscopy, molecular tests, drug susceptibility testing or follow up examinations.

Sputum collection centres are dedicated locations where sputum samples are collected, packaged and then transported to nearby TB diagnostic centres. It could be attached to any near-by health-facility as well.

Requirements of a Sputum Collection Centre

To function as sputum collection centres, the following is essential:

• Linkage/ mapping (time and distance) to testing laboratory
• Availability of adequate number of sputum cups and falcon tubes, logistics for sample packaging and transport
• Identification of open areas for sputum collection
• Staff trained in NTEP guidelines on sputum collection, sample packaging and transport, complete and correct documentation of laboratory request form, and infection control practices
• Feasibility and financial measures required for sample transport
• Inclusion of local volunteers, courier services, sample transportation under National Health Mission Free Diagnostic Services or other mechanisms as decided by the state/district
• Availability of Information, Education and Communication (IEC) material, training modules, and job-aids
   

 Sputum collection centres are established in:

• Ayushman Bharat Health and Wellness Centres/Sub-centres
• Urban primary health centres
• Tribal, hilly, desert and difficult-to-reach areas of the country

Resources

• Training Modules for Programme Managers and Medical Officers
• Operational Guidelines for TB Services at Ayushman Bharat Health and Wellness Centres
• Mycobacteriology Laboratory Manual, GLI Initiative, 2014

Assessment: