CBNAAT Testing Process Overview

Cartridge-based Nucleic Acid Amplification Test (CBNAAT) is used to detect Mycobacteria tuberculosis and rifampicin-resistance using GeneXpert IV Dx system and the Xpert MTB/ RIF cartridge.

The CBNAAT system integrates and automates sample processing, nucleic acid amplification, and detection of Mycobacteria tuberculosis and rifampicin resistance.

The system utilises the use of single-use disposable CBNAAT cartridges that hold the Polymerase Chain Reaction (PCR) reagents and hosts the PCR process.

The process involves the following steps:

1. Sample processing: Specimens are processed by adding the sample reagent at 2:1 (v/v) ratio to the sputum sample, mixing and incubation for 15 minutes at room temperature. The sputum sample get liquified after the processing step.
2. Loading sample into cartridge: Liquefied sample is added to the cartridge using a transfer pipette.
3. Setting up the machine to run the test: After switching on the system, “Create Test” (Figure A) is clicked in the GeneXpert Dx system window, test details are added, the barcode label of the cartridge is scanned (Figure B) and “Start Test” (Figure C) is clicked to initiate testing.

Figure: Setting the machine to run the assay by creating test (A), adding test details, scanning barcode (B) to start test (C); Source: GLI Training Package for CBNAAT.

4. Loading the cartridge: The instrument module door which displays the blinking green light is opened to load the cartridge. The door of module is closed firmly (an audible click sound should be heard). The green light stops blinking when the test starts.
5. Obtaining the results: When the test is finished, the green light turns off. It takes around 1 hour 55 minutes to complete test run. On completion of test run, the result is generated automatically on the monitor.
6. Ending the test run: When the system releases the door lock at the end of run, the module door is opened to remove the cartridge. The used cartridge is discarded.

Resources

• GLI Training Package for CBNAAT.  
• FIND Diadnosis for All, CBNAAT SOP.

Assessment