Evaluation of a colorimetric test for the determination of alpha-amylase with p-nitrophenylheptaoside as substrate.

A continuous method for the determination of alpha-amylase activity with a defined substrate has been published by Rauscher et al. in Berichte der Osterreichischen Gesellschaft für Klinische Chemie 4, 150 (1981). It offers the following advantages: good practicability, easy adaptation to analysers and short incubation time. Twenty-one laboratories took part in a multicentric study on this method, working with different instruments and manual procedures at three temperatures. Additionally, all laboratories participated in a laboratory improvement program, in order to discriminate systematic from accidental errors. Data on imprecision, linearity, interferences and comparability of the method have been presented at a workshop. The resulting coefficients of variation for imprecision in series as well as from day to day were 0.6-6.3% and 1.3-7.7%, respectively. No interferences from bilirubin, glucose, maltose and 37 selected drugs were found. The results from the described method correlate well with those from an UV-test (substrate: maltoheptaose); compared with other methods, however, the expected systematic deviations were observed. Reference values for 25, 30 and 37 degrees C are indicated in this report.