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Step 3.1 – Select, procure, install and set up equipment
An essential step in the implementation process is selecting appropriate instruments that fit the needs of the clinical or microbiological laboratory, and can be used to perform the new diagnostic test. The most suitable instrument for a country will depend on the intended use of, and demand for, the diagnostic test. It is important to choose an instrument that is widely available and has good supply distribution and support from the manufacturer. In addition to the testing instrument, some tests will require the use of specialized ancillary instruments.
To bring cost efficiency to testing services, a priority should be to consider the integration of TB testing with existing platforms in locations where integrated testing is feasible (59). In settings where TB diagnostic services are standalone and there is a high workload for TB testing, dedicated instruments may be preferred.
Whichever instrument is selected, expert set-up will generally be required, with the manufacturer’s engineers or authorized service providers performing the installation. Some of the MC-aNAATs may require infrastructure to be modified to accommodate the instruments. Potential set-up complexities include power supply and backup options, electrical and network connections, environmental conditions for the laboratory (e.g. maximum temperature), biosafety and ventilation requirements, computing hardware and software, a maintenance plan (e.g. weekly, monthly or pre-run checks), equipment warranty and necessary training.
Guidance for selecting which mWRD to implement has been published in the Manual for selection of molecular WHO-recommended rapid diagnostic tests for detection of tuberculosis and drug-resistant tuberculosis (15). Guidance on selecting NGS equipment is available elsewhere (33).
For TB infection skin tests, a standalone or medical-grade refrigerator for storing consumables (tuberculin or TB antigens), vaccines and medications must be available, as must backup generators or power supply system. Tuberculin vials should be stored at 2–8 °C (35–46 °F), protected from light, in the original packaging and separated from other similar vials (to avoid confusion). For IGRAs, material for blood sample collection is necessary.
Step 3.2 – Verify and maintain instruments
All instruments must be documented as being “fit for purpose” through verification with known positive and negative materials before starting to test clinical specimens. Instrument verification is conducted at installation, after service or calibration, or after moving instruments.
To ensure quality, reproducibility and reliability, maintenance and calibration must be performed regularly. The frequency of calibration and its intervals vary for each instrument. To decide on the frequency of calibration, the manufacturer’s recommendations should be followed at a minimum. However, where it is suspected that the level of accuracy of the equipment is declining, those responsible should be able to discern the problem and take the initiative to perform calibration.
Laboratory equipment calibration requires an association between measurements of a scale or accuracy that have been made or set with the equipment to be tested, and similar measurements that have been made with the standard (i.e. equipment with known or assigned accuracy). Standards vary among countries, depending on the type of industry. Manufacturers designate their measurement criterion; they also recommend the frequency and level of calibration, depending on how often the device is used and the specific application.
Many tests rely on precision instruments that require regular preventive maintenance, and ad hoc servicing and maintenance. The end-user should perform regular preventive maintenance to ensure good performance of the instrument. Suppliers or authorized service providers should perform on-request maintenance, as necessary. To ensure continued functioning of the instruments, countries should take advantage of all-inclusive and transparent maintenance contracts; these contracts should have clear service and maintenance terms and associated costs.
Step 3.3 – Assess site readiness and ensure a safe and functional testing site
The NTP or NTRL usually determines which sites will conduct diagnostic testing, based on factors such as TB epidemiology, geographical considerations, testing workload, availability of qualified staff, efficiency of referral networks and access to services for people being tested. Each testing site should be evaluated for readiness using a standardized checklist before testing of clinical specimens at the site begins. In addition, testing sites should be assessed regularly for safety and operational functionality.
A functional testing site requires the instruments used for testing to be properly positioned in a clean, secure and suitable location. Most instruments will require an uninterrupted supply of power, and appropriate working and storage conditions (e.g. humidity and temperature controlled). A safe environment requires WHO biosafety recommendations for conducting the diagnostic test to be followed in appropriate containment facilities with adequate ventilation; it also requires appropriate personal protective equipment to be used, and biological waste to be disposed of safely and in accordance with regulations. Failure to provide a functional and safe work environment can affect the health and well-being of testers, and the quality and reliability of testing.