ReacciónUninterrupted availability at all testing sites of skin test materials, or reagents and disposables for IGRAs, is essential. Careful assessment of consumption rates is necessary to avoid shortage or excessive wastage of materials according to their shelf life.
Step 5.1 – Review forecasting, ordering and distribution procedures
The following measures will be required to ensure an uninterrupted supply of skin test materials, or IGRA reagents and disposables:
- ensuring that qualified laboratory and nursing staff have input into defining the specifications for reagents, consumables and equipment; and streamlining of 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 test materials with 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 the 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;
- regular reassessment of purchasing and distribution strategies, to ensure that they are responsive to needs and the current situation; and
- coordination with the NTP to ensure that there is adequate drug supply to treat the cases of TB infection detected.
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 (66). Tuberculin is not listed among the supplies in the Global Drug Facility list; this can hamper the acquisition and distribution of pre-qualified material. This is being addressed for TBST consumables. Availability of TBST may help to overcome some of these challenges in the near future.
Step 5.2 – 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.
Once the tuberculin 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 after use for the day, at the prescribed temperature. Any remaining tuberculin must be discarded after 30 days. The duration varies for TBST; hence, manufacturer specifications should be followed.
For IGRAs, 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 level (e.g. at the national tuberculosis reference laboratory) or regional level, to ensure that kits with test failures are not distributed. For QC, WHO recommends using positive and negative controls when testing new batches of reagents.