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To address specific potential risks, the following biosafety requirements¹⁴ ¹⁵ should be established in a low-risk TB laboratory.
1. Use of bench spaces: The bench used to process specimens for direct sputum-smear microscopy or the Xpert MTB/RIF assay should be separate from areas used to receive specimens and from administrative areas used for paperwork and telephones.
The WHO consolidated guidelines on tuberculosis: tuberculosis preventive treatment include recommendations for the four milestones in the cascade of preventive care, namely identification of risk groups, TB screening and ruling out TB, testing for TBI, and choice and administration of the TPT regimen. The second edition of the TPT guidelines will have the same scope.
Overall, serious adverse events leading to death or requiring withdrawal of TPT occur rarely. It is nevertheless critical to identify any sign of drug toxicity as soon as possible and to manage it immediately, particularly because people on TPT are usually healthy. Unmanaged drug toxicity may not only harm individuals but can also damage the reputation of a programme and result in widescale suspension of TPT due to loss of public confidence. As in any preventive action, health-care providers must weigh the risks and benefits of TPT for each individual.
Giving TPT to someone who has TB disease can delay resolution of disease and favour the emergence of drug resistance. Excluding TB disease before initiating preventive treatment is one of the critical steps in the TBI care pathway. This section proposes approaches for ruling out TB disease and diagnosing TBI in people at risk of TB according to HIV status, symptoms, household contact, other risk factors, age, TBI test results and abnormality on CXR (Fig.1).
The Global Tuberculosis Programme of the World Health Organization (WHO) gratefully acknowledges the contributions that many individuals and organizations (listed in Web Annex A) have made to the development of these guidelines.
Individuals receiving TPT should be monitored at every contact with health-care providers. It is important to determine non-adherence as early as possible in order to take corrective action. Monitoring is particularly important at the beginning of treatment, when people are getting used to the routine and their medication. Afterwards, monitoring may be done monthly or more frequently as required for care of people on TPT or as per national policy.
A thimble connection (see Figure 3) is used with Class II type A2 BSC that is ducted to the outside. The thimble fits over the cabinet’s exhaust housing, sucking the air expelled from the cabinet into ducts that lead outside. A small opening (usually 5 cm wide) is maintained between the thimble and the cabinet’s exhaust housing. This opening enables room air to be drawn into the exhaust ducting system. The capacity of the exhaust system must be sufficient to capture both room air and the cabinet’s exhaust.
Class II BSCs differ from Class I cabinets in that they allow only air from a HEPA-filtered (sterile) supply to flow over the work surface.
A Class II type A2 BSC is shown in Figure 2. An internal fan draws room air (supply air) into the cabinet through the front opening and then into the front intake grill. After passing through the grill, the supply air is drawn upwards and through a HEPA filter before flowing downwards over the work surface.