A guide to aid the selection of diagnostic tests.

In recent years, a wide range of diagnostic tests has become available for use in resource-constrained settings. Accordingly, a huge number of guidelines, performance evaluations and implementation reports have been produced. However, this wealth of information is unstructured and of uneven quality, which has made it difficult for end-users, such as clinics, laboratories and health ministries, to determine which test would be best for improving clinical care and patient outcomes in a specific context. This paper outlines a six-step guide to the selection and implementation of in vitro diagnostic tests based on Médecins Sans Frontières' practical experience: (i) define the test's purpose; (ii) review the market; (iii) ascertain regulatory approval; (iv) determine the test's diagnostic accuracy under ideal conditions; (v) determine the test's diagnostic accuracy in clinical practice; and (vi) monitor the test's performance in routine use. Gaps in the information needed to complete these six steps and gaps in regulatory systems are highlighted. Finally, ways of improving the quality of diagnostic tests are suggested, such as establishing a model list of essential diagnostics, establishing a repository of information on the design of diagnostic studies and improving quality control and postmarketing surveillance.