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The usefulness and validity of a diagnostic test are key issues to deal with when considering the effectiveness of a diagnostic in clinical settings. In an era when major thoughts drift towards the elimination of infectious diseases in developing countries, notably with eradication agendas announced for major diseases of public health importance, it is of great necessity to consider diagnosis as a key element in this process. Firstly, diagnostic strategies change along the disease control continuum from morbidity control to infection control through surveillance. This, and many other limitations of current diagnostics has made way for a dramatic increase in technologies for better diagnostics to meet these needs. With a great number of products in the diagnostics production pipeline, it is of importance for developing country scientists to build capacity in diagnostic research including diganostic trials.Among the possible questions about the relation between a putative diagnostic test and a target disorder, four appear to be relevant. 1. Do test results in patients with the target disorder differ from those in normal people? 2. Are patients with certain test results more likely to have the target disorder than patients with other test results? 3. Does the test result distinguish patients with and without the target disorder among patients in whom it is clinically reasonable to suspect that the disease is present? 4. Do patients who undergo this diagnostic test fare better than similar patients who are not tested? The fourth question is even more important as the ultimate value of a test is measured in the health outcomes that follow therapeutic intervention. With this in mind, it is time for global health scientists to consider diagnostic interventions with its unique characteristics and its capabilities to provide useful evidence base for interventions that will support disease elimination.