In a single-use handheld diagnostic test device and an associated system and method, a biological and/or environmental test sample is received and reacted with reagents. The test device tests a single sample and includes a sensor to detect test data. The test device mates with, and transmits the test data to, an electronic device. A processor of the electronic device applies algorithms to the test data to generate highly sensitive and accurate quantitative test results. A presentation element of the electronic device presents the test results to a user. The test device is adapted for disposal, or for sterilization and re-use, after the electronic device receives the test data. The electronic device may be, for example, a mobile communications device, a personal digital assistant, a laptop computer, a navigation device, a digital audio player, a camera, or a gaming device.