Analysis system for the photometric determination of an analyte in a body fluid

A method for the photometric determination of an analyte in a body fluid using an analysis system comprising an analysis instrument and a test carrier, the test carrier having an evaluation zone, in which a photometrically detectable change occurs as a result of a reaction of a sample of the body fluid contacted with the test carrier with a reagent contained in the test carrier, and the analysis instrument comprising an optical emitter for emitting light, an optical receiver for receiving light, a measuring and evaluation device having a measuring unit and an evaluation unit, the method comprising the following steps:

• a) emitting light from the emitter onto the evaluation zone of the test carrier;
• b) receiving light from the evaluation zone;
• c) generating a measurement signal corresponding to the received light;
• d) amplifying and digitizing in the measuring unit the measurement signal generated by the receiver;
• e) determining in the analysis unit the desired concentration value from the digitized measurement signal using an evaluation algorithm which comprises an assignment between values of the digitized measurement signal and concentration values, the assignment being specific to the production method, at least one computing step being executed by a processor in the evaluation algorithm,
• f) acquiring the concentration value in the evaluation unit at an acquisition point in the algorithmic sequence of steps downstream from the execution of the computing step;
• g) verifying the concentration value using a control algorithm by
• g1) assigning a plurality of reference measurement values to a plurality of reference concentration values using a reference assignment;
• g2) determining the reference concentration value using the reference assignment from a reference measurement value;
• g3) using the reference assignment in the control algorithm;
• and
• g4) determining a deviation of the determined concentration value from the reference concentration value using the reference assignment;
• and
• h) recognizing an error of the measuring and evaluation device if the deviation of the concentration value from the reference concentration value exceeds a predefined limiting value.