event
Thursday 08 Dec 2011: Development of magneto-optic diagnostic technology
Professor David Newman - University of Exeter
Harrison 170 (3D Visualisation Suite) 14:00-15:00
This presentation will review how techniques developed originally for the readout of information from the first generation of optical disks have been deployed to create a new diagnostic technology for malaria and potentially many other diseases.
Up to 50% of the world's population is estimated to be at risk of exposure to malaria but its rapid and accurate diagnosis in locations remote from clinical laboratory facilities remains problematic. Although increasingly relied on the performance of antigen detecting rapid diagnostic test (RDT) sticks under the non-ideal conditions and circumstances prevailing in remote locations is known to be unsatisfactory. Studies by the WHO found wide variability in the performance of these devices especially for parasite densities below about 200 parasites/ul [1]. Detection rates were dramatically reduced to less than 75% in more than half the types of device tested with some products returning values as low as 25%. Moreover, in the worst case scenarios only 60% of health workers conducted the test with sufficient rigor to obtain the correct result and even the briefest exposure to temperatures much higher than 30oC, such as easily encountered during transport were found associated with significantly degraded performance. A less environmentally sensitive and more user friendly diagnostic test is urgently required for use in most circumstances where need is greatest. Over the past five years a reagent free test based on a magneto-optics has demonstrated the potential to meet this need [2]. Its diagnostic principle uses measurement of the Extraordinary Cotton-Mouton effect to perform a quantitative volumetric assay of the haemozoin produced by the malaria parasite as it metabolises haemoglobin. Under early blind clinical evaluation both in Kenya and the laboratory, prototype instrumentation operating on this principle attained performance levels for sensitivity and specificity of 78.5% and 72.6% respectively [3]. The newly developed handheld version of the technology shown has achieved a detection sensitivity approximately equal to 20 Plasmodium falciparum parasitized red blood cells per microlitre (PRBCs/ul) using samples created by the serial dilution of a malaria culture with fresh blood.
[1] Malaria Rapid Diagnostic Test Performance, Round 2, Results of WHO product testing of malaria RDTs (2009), April 2010, ISBN 978 92 4 159946 7
[2] D. M. Newman et al. Biophys. J. 95, 994-1000 (2008)
[3] P.F. Mens et al. Malaria J. 9, 207 (2010)
