STLS: Ensuring Smooth functioning of Lab Services

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.

All these bags are to be labelled with the Biohazard logo (figure below) on them. 

Figure: Biohazard Logo

• Waste generated in the Culture Drug Susceptibility Testing (CDST) laboratories is autoclaved prior to segregation in colour-coded bags.
• The biohazard materials are collected and handed over to handlers authorized by the pollution control board.
• Personnel handling/segregating biomedical wastes must use appropriate Personal Protective Equipment (PPE) and should be trained in spill management.

Resources

• Guidelines for Programmatic Management of Drug-resistant Tuberculosis in India, 2021.
• Guidelines for Management of Healthcare Waste as per Biomedical Waste Management Rules, 2016.

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Disinfectants used in lab settings include:

1% Sodium Hypochlorite

• Broad spectrum antimicrobial action
• Used to disinfect surfaces
• Used to disinfect infectious material and disposal of used Truenat consumables (reagent bottles, cartridges, tips, chips) 
• Hazardous and corrosive, to be used with care
• Is highly alkaline so can corrode metal
• Waste soaked in Sodium Hypochlorite should not be discarded by autoclaving. 

70% Alcohol

• Bactericidal action
• Used for surface decontamination only
• Highly inflammable; keep away from fire
• Used to disinfect biosafety cabinets, laboratory benches and surface of instruments.

5% Phenol

• Used for decontaminating Cartridge-based Nucleic Acid Amplification Testing (CBNAAT) equipment and single-use items like CBNAAT cartridges prior to disposal
• Highly irritating to the skin, eyes and mucous membranes.

Preparation of these disinfectants is described below.

Preparation of 1% Sodium Hypochlorite

• Use commercially available 4% sodium hypochlorite solution.
• Dilute with distilled water to prepare required amount of 1% sodium hypochlorite
  • E.g.: To prepare 100 ml of 1% sodium hypochlorite: 75 ml distilled water plus 25 ml 4% sodium hypochlorite solution.
• Sodium hypochlorite solutions (domestic bleach) contain 50 g/l available chlorine, and should therefore be diluted to 1:50 or 1:10 in water to obtain the final concentrations of 1 g/l or 5 g/l when used as a general-purpose disinfectant for TB laboratories.
• To be prepared fresh.

Preparation of 70% Alcohol

• Use commercially available absolute alcohol.
• Dilute with distilled water to prepare the required amount of 70% alcohol
  • E.g.: To prepare 100 ml of 70% alcohol: 70 ml absolute alcohol plus 30 ml distilled water.

Preparation of 5% Phenol

• Melt 5 g of phenol by heating it.
• Dissolve in 100 ml distilled water.

Video : Preparation of TB Lab Disinfectants

Resources

• Tuberculosis Laboratory Biosafety Manual

The Laboratory Technician (LT) must safely discard contaminated, biohazard waste generated by tuberculosis (TB) laboratories. This waste must be discarded along with the overall waste of the health facility in which TB services are provided.

There are 2 types of waste generated from DMC laboratory settings:

1. Sputum containers with specimen and wooden sticks
2. Stained slides

Disposal of Sputum Cups with Left-over Specimen, Lids and Wooden Sticks

Figure 1: Steps for disposal of sputum cups with specimen, lids and wooden sticks

Important Points to Remember

• If autoclaving is not possible, boil in a pressure cooker of 7 litre capacity with water and submerge the contents for at least 20 minutes
• LTs and support staff handling biological waste need to wear gloves
• The red bag used for autoclaving must:  
  • Have a biohazard symbol  
  • Have adequate strength to withstand the load of the waste material 
  • Be made of non-PVC plastic material  

Disposal of Stained Slides

Figure 2: Steps for disposal of stained slides

Resources

• Training Module (1-4) for Program Managers and Medical Officer, NTEP, MoHFW, 2020.

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It is essential to follow biosafety protocols while handling specimens and cartridges. This will prevent anyone handling the specimens and cartridges from getting infected.

General Biosafety Requirements for CBNAAT

Cartridge-based Nucleic Acid Amplification Test (CBNAAT) is a low-risk procedure and requires the same level of precautions, like those used for direct Acid-fast Bacillus (AFB) sputum smear microscopy:

1. Carry out the procedure in a well-ventilated area.
2. Wear gloves and a laboratory coat at all times when handling patient samples.
3. Minimize the generation of aerosols during sample processing and handle specimens carefully and responsibly.

Based on risk assessment, additional biosafety precautions may be required in CBNAAT laboratories, such as the use of N95 respirators or biosafety cabinets.

Personal Protective Equipment (PPE) is important, but it does not replace good microbiological and good laboratory practices. They include:

Gloves: Essential (disposable and powder-free)

Laboratory coats: Essential

Respirators: Usually not required, but:

• May be needed, based on risk assessment.
• Must always be included in a spill kit.
• Recommended respirators are N95 or chosen based on program guidelines.

Precautions to take while preparing samples for CBNAAT testing

• The sample reagent should be added to the specimen in such a manner that the procedure minimizes aerosol generation.
• Although the sample reagent inactivates M. tuberculosis bacilli, it reduces, but does not eliminate, the biosafety risk to the laboratory technician.
• There is an increased risk of generating aerosols when splitting and handling concentrated and extrapulmonary TB specimens. These procedures must be performed in a certified biosafety cabinet.

Precautions during cartridge loading and transport

• When transferring cartridges to the machine for loading, an appropriate size enclosed container should be used.
• Care should be taken, as samples may leak if the cartridges are toppled during transport.

Resources

• GeneXpert MTB/RIF Assay Package Insert.

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Disposal of biohazardous waste is essential to prevent contamination and possible infection of those handling the infected specimens.

At the end of each day, Cartridge-based Nucleic Acid Amplification Test (CBNAAT) laboratories generate contaminated material such as:

• Used sputum containers
• Used cartridges
• Transfer pipettes.

All used materials should be considered contaminated.

All infectious samples should be sealed in a biohazard bag and disposed off according to Biohazard Waste Disposal Guidelines under the National Pollution Control Guidelines, 2019.

• Contaminated materials should be picked up with a gloved hand and placed in a closed lid container of 5% phenol solution or a biohazard bag.
• At the end of the day, the phenol should be drained, and the materials/ bags should be autoclaved at 121°C at 15 psi pressure for 20 minutes.
• Once done, the materials should be cooled and sent to the common waste treatment facility for mutilation/ shredding or disposal.

It is a good practice to display the Standard Operating Procedures (SOPs) for the disposal of each item in the CBNAAT laboratory.

Resources

• Guidelines for Management of Healthcare Waste as per Biomedical Waste Management Rules, 2016