Development of medical point-of-care applications for renal medicine and tuberculosis based on electronic nose technology

INTRODUCTION: Current clinical diagnostics are based on biochemical, immunological or microbiological methods. However, these methods are operator dependent, time consuming, expensive and require special skills, and are therefore not suitable for point-of-care testing. Recent developments in gas-sensing technology and pattern recognition methods make electronic nose technology an interesting alternative for medical point-of-care devices. METHODS: We applied a gas sensor array based on 14 conducting polymers to monitor haemodialysis in vitro and to detect pulmonary tuberculosis in both culture and sputum. RESULTS and DISCUSSION: The electronic nose is able to distinguish between control blood and “uraemic” blood. Furthermore, the gas sensor array is not only capable of discriminating pre- from post-dialysis blood (97% accuracy) but also can follow the volatile shift occurring during a single haemodialysis session. The electronic nose can be used for both dialysate side and blood-side monitoring of haemodialysis. The pattern observed for post- and pre-dialysis blood might reflect the health status of the patients and can therefore be related to the long-term outcome. Furthermore, the gas sensor array was also able to discriminate between Mycobacterium spp. and other lung pathogens such as Pseudomonas aeruginosa. More importantly the gas sensor array was capable of resolving different Mycobacterium spp. such as Mycobacterium tuberculosis, M. scrofulaceum, and M. avium in both liquid culture and spiked sputum samples. The detection limit for M. tuberculosis in both sputum and liquid culture is 1 x 104 mycobacteria ml-1 and therefore partially fulfils the requirement set by the WHO. The gas sensor array was able to detect culture proven TB with a sensitivity of 89% and a specificity of 91%. CONCLUSIONS: In conclusion, this study has shown the ability of an electronic nose as a point-of-care device in these areas.