Comparison between a New Chromogenicα-Amylase Test (Phadebas) and the Wohlgemuth Amyloclastic Method in Urine

Abstract

The ‘Phadebas Amylase Test’ and the Wohlgemuth amyloclastic method were compared in urine samples. A highly significant linear correlation was found when the Phadebas amylase values were expressed in logarithmic form and the Wohlgemuth values as the nth power of two. For urine of very high α-amylase activity (> 13,000 U/1, 30 °C equal to 1024 Wohlgemuth units - our normal α-amylase values are 40–1500 U/1, 30 °C), the substrate in one ‘Phadebas Amylase Test’ tablet does not keep the enzyme saturated and the correlation falls off from linearity. Dilution of the urine with distilled water or 0.9 % NaCl was tested but found to be unsatisfactory. With a constriction pipette of Lang-Levy type a small but accurate volume of urine can be used for analysis (e.g. 1 to 2 μl). However, since urinary α-amylase activity is inactivated considerably at high dilutions (more than 1 in 400) even if the sample is added directly to the Phadebas reaction mixture, it is recommended that 0.02–0.05 per cent of bovine serum albumin should always be included in the ‘Phadebas Amylase Test’ reaction mixture to prevent inactivation.