A wearable device includes a detector configured to detect a response signal transmitted from a portion of subsurface vasculature, the response signal being related to binding of a clinically-relevant analyte to functionalized particles present in a lumen of the subsurface vasculature. Program instructions stored in a computer readable medium of the device, and executable by a processor, may cause the device to determine a concentration of the clinically-relevant analyte based on the response signal detected by the detector； determine whether a medical condition is indicated based on at least the concentration of the clinically-relevant analyte； and, in response to a determination that the medical condition is indicated, transmit data representative of the medical condition via the communication interface. The device may also include a signal source configured to transmit an interrogating signal into the portion of subsurface vasculature, thereby generating a response signal in response to the interrogating signal.
