LT-Microscopy & NAAT

Ventilation is defined as the supply/ distribution/ exchange or removal of air from spaces by mechanical or natural means.

Mycobacterium tuberculosis is transmitted in airborne particles called droplet nuclei that are expelled when a person with pulmonary TB coughs, sneezes, shouts, or sings. People nearby may breathe in these bacteria and become infected. 

Airborne infection control is essential to prevent the spread of TB within a health facility and other settings.

Hierarchy of Controls to Reduce Risk of Transmission of TB (see the Figure)

The Medical Officer (MO) of Designated Microscopy Centre (DMC) is responsible for determining the amount of reagents and other materials the DMC needs every month.

The Senior TB Laboratory Supervisor (STLS) will make sure these supplies are distributed in a timely manner, usually on a monthly basis or as and when required.

After air drying and heat-fixing of the smear, it needs to be stained.

Fluorescence microscopy (FM) staining should always be carried out in a designated area. The reagents required for the FM staining procedure are shown in Figure 1. The steps involved in the staining procedure are shown in Figure 2.

Figure 1: Reagents Required for FM Staining

Results of Ziehl–Neelsen (ZN) and Fluorescence Microscopy (FM) are added to Nikshay Diagnostic Module. After a patient is registered, test details are added which then leads to the page to add details on sample type, facility and test results (Figures 1-6).

Features of Nikshay Diagnostic Module

After air drying and heat-fixing of the smear, it needs to be stained for the identification of MTB during microscopy.

The reagents required for the ZN staining procedure are shown in Figure 1. The steps involved in the staining procedure are shown in Figure 2.

Figure 1: Reagents Required for ZN Staining

For sputum smear microscopy, the slides should be air-dried as heating the slide while the smear is wet can result in bubbling of TB bacilli into the air.

Fixation makes the sputum stick to glass slide and preserves the shape of the bacilli. 

The procedure for air-drying and heat-fixing the slide is as follows:

Storage conditions of sputum sample can effect the test results.

• Sputum samples should be transported to the laboratory as soon as possible after collection.
• It is the responsibility of Laboratory Technician (LT) and Senior TB Laboratory Supervisor (STLS) to ensure proper storage and transport of sputum specimens.
• Sputum is stored to preserve the specimen quality.
• The stored sputum samples should not be frozen.

Storage of Sputum Samples

For microscopy

The binocular microscope requires considerable care in its use, regular cleaning, and protection from dust and fungal growth.

Annual maintenance of a microscope includes:

Regular cleaning of microscope is essential to ensure that it is optimally functioning. Cleaning is important to remove dirt, lens immersion oil and ensure disinfection. It involves cleaning the lenses, the body, the stage of the microscope and the light source. The microscope needs to be cleaned daily and the lenses need to be cleaned after each use.

Materials used for cleaning: