Opinião
Step 4.1 – Review forecasting, ordering and distribution procedures
Uninterrupted availability of reagents and disposables at the testing site is essential to ensure that technical capacity is built in the early stages of implementation (avoiding long delays between training and the availability of reagents and disposables), and to ensure consistent service during routine use. The following measures will be required to ensure uninterrupted supply of reagents and disposables:
- ensuring that qualified staff contribute to defining the specifications for reagents, consumables and equipment;
- streamlining importation and in-country distribution procedures to ensure sufficient shelf life of reagents and consumables, once they reach testing sites;
- careful monitoring of consumption rates, tracking of reagent-specific shelf lives and forecasting to avoid expirations or stock-outs;
- careful planning to ensure that sites have received training, and that equipment has been installed ahead of shipment of reagents;
- ongoing monitoring of all procurement and supply chain steps, to ensure that delays are minimized and that sites receive correct reagents as per the planned schedule; and
- regular reassessment of purchasing and distribution strategies, to ensure that they are responsive to needs and the current situation.
There has been a global shortage of tuberculin in recent years, with a direct impact on TB infection screening in countries that rely on TST (67). Tuberculin is not listed among the supplies in the Global Drug Facility list; this can hamper the acquisition and distribution of prequalified material. This situation is being addressed for TBST consumables; increased availability of TBST may help to overcome some of these challenges in the future.
Step 4.2 – Develop procedures to monitor reagent quality and shelf life
The shelf life of reagents and their required storage conditions must be considered when designing a procurement and distribution system. Laboratory managers should routinely monitor reagent quality and shelf life to ensure that high-quality test results are generated. Also, the laboratory must establish SOPs for handling the reagents and chemicals used, to ensure both quality and safety. For example, the shelf life of NGS reagents is normally short; hence, robust planning is required to avoid kits expiring, with resulting high costs for testing. For tuberculin, once the vial has been opened, the material should be used within 30 days; thus, the date of opening should be clearly written on the label of the vial. The vial should be stored immediately at the end of the working day, at the prescribed temperature. Any tuberculin remaining after 30 days must be discarded. The duration varies for TBST; hence, manufacturer specifications should be followed.
New-lot testing, also known as lot-to-lot verification, should be performed on new batches of reagents or test kits. Such testing usually involves testing a sample of the new materials and comparing the results to an existing lot of materials with known performance. Where possible, new-lot testing of commercially available test kits should be performed at the central (e.g. NTRL) or regional level, thereby ensuring that kits with test failures are not distributed. At the testing site, new-lot testing is needed for reagents prepared at that site; it may also be needed to monitor conditions during transport and storage of test kits within the country. For QC, WHO recommends using positive and negative controls when testing new batches of reagents.