Direct sputum smear microscopy is the most widely used means for diagnosing pulmonary TB and is available in most primary health-care laboratories at health-centre level. Most laboratories use conventional light microscopy to examine Ziehl-Neelsen-stained direct smears; this has been shown to be highly specific in areas with a high prevalence of TB but with varying sensitivity (20–80%).

Fluorescence microscopy is more sensitive (10%) than conventional Ziehl-Neelsen microscopy, and examination of fluorochrome-stained smears takes less time. Uptake of fluorescence microscopy has, however, been limited by its high cost, due to expensive mercury vapour light sources, the need for regular maintenance and the requirement for a dark room.

LED microscopy was developed mainly to give resource-limited countries access to the benefits of fluorescence microscopy. First, existing fluorescence microscopes were converted to LED light sources. Considerable research and development subsequently resulted in inexpensive, robust LED microscopes or LED attachments for routine use in resource-limited settings.

In comparison with conventional mercury vapour fluorescence microscopes, LED microscopes are less expensive, require less power and can run on batteries; furthermore, the bulbs have a long half-life and do not pose the risk of releasing potentially toxic products if broken, and LED microscopes are reported to perform equally well in a light room. These qualities make LED microscopy feasible for use in resource-limited settings, bringing the benefits of fluorescence microscopy (improved sensitivity and efficiency) where they are needed most.