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Similar to the moderate-risk laboratory, there are two levels of containment in a high-risk laboratory: the BSC (primary containment) and the laboratory itself (secondary containment).
In TB laboratories classified as high risk, all procedures for handling viable M. tuberculosis cultures and aqueous suspensions of TB bacilli for identification, indirect DST and molecular assays must be conducted within a BSC in a TB-containment laboratory.
In addition to the hazards described in Chapter 4 for TB laboratories classified as moderate risk, and the general risks that are addressed by the biosafety measures described in Chapter 2, laboratories classified as high-risk (or containment) also face the following challenges, all of which increase risks:
The term TB-containment laboratory refers to a facility that has the minimum design features necessary to safely manipulate TB cultures. This type of facility may or may not meet all of the requirements of a Biosafety Level 3 laboratory as described in WHO’s Laboratory biosafety manual.² All laboratory facilities must comply with local and national regulations.
In a laboratory where there is a moderate risk of infection, there are two levels of containment: the BSC (primary containment) and the laboratory itself (secondary containment). To address the specific risks associated with a moderate-risk laboratory, the following mitigation and control measures should be established.
In addition to the general risks that are addressed by the biosafety measures described in Chapter 2 (such as unauthorized persons in the laboratory, mouth pipetting, cluttered work stations, improper waste disposal), the TB laboratory classified as moderate risk also faces the following challenges, all of which increase risks:
The recommendations in this chapter are the minimum requirements needed to limit or reduce risks of infection in laboratories carrying out specific procedures that are considered to have a moderate risk of spreading TB. Additional measures may be deemed necessary following a site-specific risk assessment.
To address specific potential risks, the following biosafety requirements¹⁴ ¹⁵ should be established in a low-risk TB laboratory.
1. Use of bench spaces: The bench used to process specimens for direct sputum-smear microscopy or the Xpert MTB/RIF assay should be separate from areas used to receive specimens and from administrative areas used for paperwork and telephones.
In addition to the general risks that are addressed by the biosafety measures described in Chapter 2, the low-risk TB laboratory may also face the following challenges, all of which increase risks:
The recommendations in this chapter are the minimum requirements needed to limit or reduce risks of infection in laboratories carrying out specific procedures that are considered to have a low risk of spreading TB. Additional measures may be deemed necessary following a site-specific risk assessment.
All positive TB cultures must be autoclaved before disposal. An autoclave should be available close to or in the laboratory where TB culture is performed.
All contaminated (that is, potentially infectious) materials except sharps should be placed in disposable plastic bags before being transported for incineration. If possible, materials from TB laboratories should not be discarded in a landfill even after decontamination.