Automated processing of sputum to concentrate TB is urgently needed as the concentration of TB from sputum before microscopy can significantly improve case finding. This concentration of TB can be achieved by centrifugation or by magnetic separation by magnetic TB-Beads (please visit our publications in the Product Resource tab). The advantages of TB-Beads, are safety, speed and the potential for automation. Using the beads, the sample does not have to be removed from the biosafety cabinet and the aerosol hazards of centrifugation are avoided. In addition, using the beads a sample can be processed after sputum thinning in less than 10 minutes.
As microbiology laboratories become more automated, TB labs appear more and more of an anachronism. Processing samples is labour intensive, often subjective, prone to protocol variation from lab to lab and from one technician to another and hazardous due to the risk of infection. It is true that TB rates among staff working in TB labs is higher than might be expected for the general population and laboratory acquired infection has been well documented.
The close cousin of TB-Beads, RapiPREP beads have already been built into automated protocols for the extraction of multiple pathogens from clinical swabs. However, thinned sputum presents a unique logistical problem in that the sample itself and its volume can be highly variable with volumes of thinned sputum of 10 ml not unusual. Any processing method has to be robust and inexpensive. Processing of large volumes requires a large quantity of beads which could be expensive. Unlike tests for other pathogens eg HIV, HBV etc where well-resourced labs in can spend quite large sums of money, TB is generally handled in resource-poor laboratories in which the costs for tests are measured in cents rather than tens of dollars.
TB-beads have already been shown to extract TB from sputum with a similar robustness and efficiency to centrifugation (please visit our publications in the Product Resource tab). The cost of extraction can be as low as one dollar. In addition, work is are well underway to develop low cost automated sputum processing platforms based on TB-Beads that can handle large sputum volumes and present the extracted TB for analysis by culture, microscopy or PCR.