It is essential that TB DOTS programmes are supported by a network of laboratories providing a reliable and accurate service. Laboratories at all levels need to be managed by a system of quality assurance that meets international standards.

WHO and International Union Against Tuberculosis and Lung Disease define quality assurance for sputum smear microscopy as follows:

• Quality control is a systematic internal monitoring of working practices, technical procedures, equipment and materials, including quality of stains
• External quality assessment is a process to assess laboratory performance. It includes on-site assessments (supervisory visits), panel testing and slide rechecking
• Quality improvement is a process by which the components of smear microscopy diagnostic services are analyzed with the aim of looking for ways to permanently remove obstacles to success.