Tuberculosis is a leading cause of morbidity and mortality worldwide, especially in resource-limited settings [1
]. The WHO has made the recognition and treatment of patients with tuberculosis one of its highest priorities. Research and development of improved diagnostics is one of the main goals set in The Global Plan to Stop TB 2006-2015 (WHO) [5
]. To meet these needs, diagnostic tools must be made more adequate than currently utilized methods and must also be safe, affordable and easy to use [6
Fluorescent microscopy methods for the identification of acid-fast organisms have become the mainstay of many mycobacteriological laboratories in the United States and around the world [7
]. In standard acid-fast microscopy, the oil immersion lens is used to scan the slide (1000x magnification) while in fluorescent microscopy, lesser magnification is used, thus saving a significant amount of time on each negative slide. Fluorescent microscopy is preferred in healthcare settings with large numbers of specimens submitted for suspected mycobacterial disease.
The use of improved diagnostics including fluorescent microscopy (such as the ParaLens system) in developing nations has been limited by lack of infrastructure, trained laboratory staff and lack of funding [8
]. However, fluorescent microscopy is potentially more sensitive and less labor intensive than traditional light microscopy using the Ziehl-Neelsen or Kinyoun method for the identification of acid-fast bacilli [6
]. Thus microscopists trained using conventional fluorescent staining and dark-field microscopy will have no problem reading slides with the ParaLens, as the technology is virtually the same.
Therefore the ParaLens system is uniquely suited for application in developing countries. Lower costs than traditional fluorescent scopes provides affordability, and as demonstrated in this study, it is functional, durable, accurate and easy to use in rural, resource poor field environments and with various power options. The attachment avoids the purchase of a second microscope, since it utilizes an already existing compound microscope. Previous studies have tested a non-QBC ParaLens system utilizing a halogen bulb and fiber-optic cable, which limited the bulb life and luminosity [13
]. The use of LED bulbs in place of standard fluorescent bulbs provides extended life (estimated to be 15-30,000 hours), much longer compared to the life of a standard bulb (estimated 800 hours). The attachment can be used with standard 110V electricity, 220V electricity and with a battery for locations without electricity. The attachment compared favorably with more expensive conventional fluorescent microscopes in brightness, clarity and ease of viewing (see Figs.
). Other authors have also found that the use of such equipment can indeed provide an excellent tool for identification of mycobacteria and can be a useful alternative to conventional fluorescent microscopy [12
Fig. (2) (A). AFB stained using QBC ParaLens™ system, Auramine-O/Rhodamine B (Truant’s Modification) (60x ParaLens objective w/oil, Olympus CH40 compound microscope). (B). AFB stained using conventional fluorescent microscope, Auramine-O/Rhodamine (more ...)
Negative control (E. coli) using the QBC ParaLens™ system, (60x ParaLens objective w/oil, Olympus CH40 compound microscope).
One limitation of this study was that the results were based on known positive and negative control slides prepared in the United States. While this does not affect the durability portion of the study, it is possible that sputum samples collected from patients outside the controlled setting of a public health laboratory in the United States under field conditions in the developing world may stain differently.