In devices that determine levels of substance use, a substance level in a test sample provided to the testing device by a test subject is determined. A sequence of images are captured to include a portion of the face of the test subject providing the test sample and a display of the testing device. A value indicative of the substance level detected within the test sample is determined. A validity indicator indicating validity of the value indicative of the substance level is determined. A current location is determined. The value indicative of the substance level, the validity indicator, and the current location are sent to a remote server.
