A method of verifying proper functionalization of a sensor and a negative test result obtained by exposing a sensing element functionalized to detect a target analyte to a test sample is described. The method may include, subsequent to or simultaneously with the exposing the sensing element to the test sample, exposing the sensing element to a test confirmation sample, the test confirmation sample comprising at least one of the target analyte in an amount greater than a detection limit of the sensing element and a recombinant protein of the target analyte in an amount greater than a detection limit of the sensing element and performing a measurement using the sensing element to obtain a subsequent test result.