STLS

External Quality Assurance (EQA) ensures that high-quality testing can be carried out efficiently and without interruption. It involves Proficiency Testing (PT) and On-site Evaluation (OSE).

PT is an important component of EQA for Cartridge-based Nucleic Acid Test (CBNAAT) under the National TB Elimination Program (NTEP) and guarantees accurate and reproducible results.

Importance of EQA/ PT for CBNAAT

On completion of a test run, the Cartridge-based Nucleic Acid Amplification Test (CBNAAT) gives the following results:

1. MTB DETECTED; Rif Resistance DETECTED
2. MTB DETECTED; Rif Resistance NOT DETECTED
3. MTB DETECTED; Rif Resistance INDETERMINATE
4. MTB NOT DETECTED
5. Error
6. Invalid
7. No result

Conclusive results include: MTB NOT DETECTED, MTB DETECTED with Rif Resistance/ without Rif Resistance.

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:

False result: It’s a situation where the test result is different from the truth.

Types of False Results

• False Positive: When the test result is positive but the patient does not have TB.
• False Negative: When the test result is negative but the patient has TB.

Both cases will lead to wrong categorization and incorrect treatment. The consequences of false results are shown in the figure below:

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. 

The National TB Elimination Programme (NTEP) utilizes different coloured bags for the segregation of waste generated in TB laboratory settings as shown in the table below.

The National TB Elimination Program (NTEP) recommends freshly preparing reagents from commercial procured products, at the District TB units to be used for microscopy. Chemicals need to be carefully monitored for potency and the calculation needs to be accurate while preparing reagents for smear microscopy.

For Preparing 1% Carbol Fuchsin (500ml): The required chemicals and materials for preparing 500 ml Carbol Fuchsin are:

1. Basic Fuchsin

Standard Operating Procedure (SOP) for Packaging Specimen during the transportation of biological specimens for TB diagnosis, also known as Triple Layer Packaging, is as follows:

The Lab Technicians (LTs) at the Designated Microscopy Centres (DMCs) should be trained to carefully pack the sputum samples in the cold box to avoid spillage of the samples. Before packing, personal protection measures such as wearing hand gloves (double gloves preferred), goggles and masks are to be followed by the LTs to prevent contracting the infection.

The Healthcare Worker (HCW) needs to carefully explain how to collect a good quality sputum specimen. He/she needs to demonstrate how to bring up sputum from the chest, what a good sputum specimen looks like, and the quantity of sputum required.  

Characteristics of a Good Sputum Sample 

Consumables required for Truenat test provided by the manufacturer include:

Trueprep AUTO MTB Sample Pre-treatment Pack for sample processing Liquefaction buffer Lysis buffer Disposable transfer pipette (graduated) - 1ml
Trueprep AUTO v2 Universal Cartridge Based Sample Prep Kit for DNA extraction