Driven by scientific progress and economic stimulus, medical diagnostics will move to a stage in which straightforward medical diagnoses are independent of physician visits and large centralized laboratories. The future of basic diagnostic medicine will lie in the hands of private individuals. We have taken significant strides towards achieving this goal by developing an autoassembly assay for disease biomarker detection which obviates the need for washing steps and is run on a handheld sensing platform. By coupling magnetic nanotechnology with an array of magnetically responsive nanosensors, we demonstrate a rapid, multiplex immunoassay that eliminates the need for trained technicians to run molecular diagnostic tests. Furthermore, the platform is battery-powered and ultraportable, allowing the assay to be run anywhere in the world by any individual.