Calibration of the Ektachem Amylase method using human reference materials and the Phadebas® Blue Starch method as an interim reference method

Abstract

In a multilaboratory study a consensus was established to calibrate the Ektachem Amylase method to reproduce the results of the Phadebas® Blue Starch method. The calibration graph has a slope = 3.39 and intercept = 25. For the Ektachem Amylase method the reaction-rate ratio between salivary and pancreatic amylase was calculated to be 0.89, relative to that of the Phadebas® Blue Starch method. A calibration value for the Nordic Amylase Calibrator to be used on Ektachem analysers was determined to be close to 469 U1⁻¹ for the current batch. However, since the difference from the stated value of 460 U 1⁻¹ is negligible, the authors recommend the use of the stated value for this and future batches of the Nordic Amylase Calibrator. An error of around 10% introduced by the presence of salivary amylase is comparable to the methods accepted by the Scandinavian Committee on Enzymes. Introduction of a consensus calibration reduced the interlaboratory variation by up to 40% at all levels.

Key Words:

• external quality assessment schemes
• intermethod calibration
• post-prediction adjustment
• SCE