DEVELOPMENT AND EVALUATION OF A REAGENT CARRIER WITH A NEW REACTION SEQUENCE FOR THE DETERMINATION OF CREATININE IN BLOOD, PLASMA, SERUM AND URINE

After a short outline of the history of creatinine determination metho ds we describe the development of a dry-reagent-carrier system for the reflometric determination of the creatinine concentration in blood, p lasma, serum and urine (Reflotron(R) Creatinine (new)). The method is based on a sequence of enzymatically catalyzed reactions producing H2O 2, but which in contrast to the previously used procedure do not lead to the formation of creatine as an intermediate. Hence, pretreatment o f sample material to eliminate endogenous creatine is no longer necess ary. In the indicator reaction, use is made of an imidazole derivative as the chromogen. The dye formed in the presence of peroxidase can be measured by reflectance photometry beyond the long-wave absorption ba nds of haemoglobin and bilirubin at 642 nm. We present in detail the r esults of the multicentre evaluation of the analytical properties of t his new test principle. The data obtained show that Reflotron(R) Creat inine (new) correlates well with the routine method Creatinine PAP, wh ich was used as a comparison method, with respect to accuracy and prec ision and even surpasses it with respect to specificity. Advantages ov er the first generation of Reflotron(R) Creatinine are: shorter reacti on time, longer stability of the reagent carrier, no interference by b ilirubin and reduced interference by haemoglobin.