Microscopy Solutions for Primary Health Care

Conventional light microscopy of Ziehl-Neelsen-stained smears prepared directly from sputum specimens is the most widely available test for detecting tuberculosis (TB) in resource-limited settings. Ziehl-Neelsen microscopy is highly specific, but its sensitivity is variable (20 to 80%) and is significantly reduced in patients with extrapulmonary TB and in HIV-infected TB patients. Conventional fluorescence microscopy is more sensitive than Ziehl-Neelsen and takes less time, but its use has been limited by the high cost of mercury vapor light sources, the need for regular maintenance and the requirement for a dark room.

Light-emitting diodes (LED) have been developed to offer the benefits of fluorescence microscopy without the associated costs. In 2009, the evidence for the efficacy of LED microscopy was assessed by the World Health Organization (WHO), based on standards appropriate for evaluating both the accuracy and the effect of new TB diagnostics on patients and public health. The results showed that the accuracy of LED microscopy with Auramine O staining was equivalent to that of international reference standards, it was more sensitive than conventional Ziehl-Neelsen microscopy, and it had qualitative, operational and cost advantages over both conventional fluorescence and Ziehl-Neelsen microscopy.

Malaria as well as African trypanosomiasis, also known as sleeping sickness, are insect-borne parasitic diseases that are widespread in developing and emerging countries. Both of these diseases cause hundreds of thousands of deaths per year when untreated. The parasites are usually identified in a patient’s blood film using a compact, upright microscope with brightfield contrast. The most common staining methods are the Giemsa, Romanowski or the Leishman stain of the blood smear.

Lightweight, compact, portable and easy-to-use microscopes with an independent power supply, a robust light source and climate-protected optics are requirements for reliable help wherever it is needed.