Diagnostic tests that are implemented should:
- provide accurate results;
- provide timely results to impact clinical decision-making;
- be justified based on need; and
- be quality assured, reliable and reproducible.
The decision on where to place a specific test is an important one that can lead to success or failure in achieving these desired outcomes. Also, a diagnostic test should not be seen in isolation from the broader ecosystem of tests (TB and non-TB) used to deliver results for clinical management.
In many resource-limited or high-burden settings, TB laboratory networks have a pyramidal structure, as shown in Fig. 3.1. This structure has the largest number of laboratories at the peripheral level (Level I); a moderate number of intermediate laboratories (Level II), usually located in mid-sized population centres and health facilities; and a single (or more than one in large countries) central laboratory (Level III) at the provincial, state or national level. Each level or tier has specific requirements for infrastructure and biosafety, defined by the activities and diagnostic methods being performed in the laboratories.