The present invention pertains to a method for verifying usability of a test element on the basis of the relation of at least one control parameter measurable from the blank test field of a test element to a standard value for the at least one control parameter. In one embodiment, the method comprises determining the deviation between a first ratio calculated from a blank-field reference value measured for the control parameter and a first standard value, and a second ratio calculated from a blank-field control value and the first standard value, and rejecting a test element if the deviation is not within a predetermined tolerance range for the deviation.