A method for determining a correct test performance for a flow test element, the method comprising the steps of: • providing a flow test element having a plurality of functional zones (3, 4, 5, 6, 7), the plurality of functional zones (3, 4, 5, 6, 7) being at least partially fluidly connected and comprising an application zone, a testing zone fluidly connected to the application zone and configured for determination of a marker in a whole blood sample, a bridging zone located between and fluidly connected to the application zone and the testing zone, and a control zone located downstream from and fluidly connected to the testing zone, wherein the bridging zone comprises a bridge membrane fluidly connected to the application zone and the testing zone configured to hinder migration of erythrocytes to the testing zone, • applying a small volume of a liquid sample to the sample application zone of the flow test element, such that the liquid sample at least partially flows to the testing zone and control zone, and • determining correct test performance for the flow test element by measuring at least one optical parameter for one or more functional zones (3; 4; 5; 6; 7), and comparing the at least one optical parameter measured to at least one predefined optical parameter assigned to the one or more functional zones (3; 4; 5; 6; 7), thereby optically determining whether a part of the applied liquid sample reaching one of the zones of the plurality of functional zones (3, 4, 5, 6, 7) is a whole blood sample, and optionally determining the marker in the whole blood sample by reading the testing zone, if correct test performance is determined, wherein if in the step of determining correct test performance non-correct test performance is detected, further analysis is interrupted. • providing a flow test element having a plurality of functional zones (3, 4, 5, 6, 7), the plurality of functional zones (3, 4, 5, 6, 7) being at least partially fluidly connected and comprising an application zone, a testing zone fluidly connected to the application zone and configured for determination of a marker in a whole blood sample, a bridging zone located between and fluidly connected to the application zone and the testing zone, and a control zone located downstream from and fluidly connected to the testing zone, wherein the bridging zone comprises a bridge membrane fluidly connected to the application zone and the testing zone configured to hinder migration of erythrocytes to the testing zone, • applying a small volume of a liquid sample to the sample application zone of the flow test element, such that the liquid sample at least partially flows to the testing zone and control zone, and • determining correct test performance for the flow test element by measuring at least one optical parameter for one or more functional zones (3; 4; 5; 6; 7), and comparing the at least one optical parameter measured to at least one predefined optical parameter assigned to the one or more functional zones (3; 4; 5; 6; 7), thereby optically determining whether a part of the applied liquid sample reaching one of the zones of the plurality of functional zones (3, 4, 5, 6, 7) is a whole blood sample,