Low-risk TB Laboratories

Depending on the procedural risk in the TB lab, the lab is classified into low, moderate and high-risk categories.

Low-risk TB laboratories work on sputum specimens for:

1. Direct Acid-fast Bacilli (AFB) smear microscopy
2. Cartridge-based Nucleic Acid Amplification Test (CBNAAT)/ Truenat

Figure 1: Procedures Conducted in a Low-Risk TB Lab

• Procedures that involve direct microscopy or killing of the mycobacteria before microscopy are taken up in these labs.
• These labs have a low risk of generating infectious aerosols from specimens and a low concentration of infectious particles.

Features and Essential Minimum Biosafety Measures of Low-risk TB Labs

1. Space requirements  

• Bench spaces should be separated from areas used to receive specimens and administrative areas used for paperwork and telephones.
• Ensure adequate ventilation; it is important to maintain natural or mechanical, directional airflow with 6-12 air changes per hour (ACH). Workstations are optional solutions.

2. Procedural requirements

To minimize the generation of aerosols:

• Carefully open specimen containers.
• Air-dry smears and use a flame to fix them.
• Use disposable wooden sticks or transfer loops.

For the handling of leaking specimen containers: Discard and request a fresh sample.

3. Personal Protective Equipment (PPE) requirements

• Protective laboratory coats should be worn at all times in the laboratory.
• Gloves must be worn for all procedures that involve direct contact with potentially infectious materials.
• Gloves should not be reused.
• Staff should always wash their hands before leaving the laboratory.
• Respirators are optional.

Figure 2: Challenges in a Low-risk TB Lab that Increase the Risk of Infection

Resources

• GLI LC Training Module on Biosafety.
• TB Lab Biosafety Manual, WHO.

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