experiments. BMC Genomics 2004;5:20. DOI: 10.1373/clinchem.2006.072876 Diffractive Optics Technology: A Novel Detection

There is an increasing need for high-sensitivity immuno-assays that can be used in point-of-care patient testing of complex media. For example, analytes such as the natri-uretic peptides and recently discovered sepsis markers are found in blood in very low picomolar concentrations (1, 2). Although advances have been made in the use of fluorescent, chemiluminescent, and other labels to mea-sure markers at lower detection limits, background inter-ference from biological samples and detection instrumen-tation remains problematic. Optical biosensors offer the promise of label-free real-time measurements, but their application to quantification of analytes in complex media is impaired by higher detection limits and is susceptible to changes in refractive indices or nonspecific surface bind-ing. Moreover, the costliness of these devices has largel