Practical aspects on the determination of serum alkaline phosphatase isoenzymes using L-phenylalanine and urea

Simple methods for estimation of the most frequently occurring alkaline phosphatase isoenzymes in serum are evaluated. Methods based on inhibition by L-phenylalanine or denaturation by heat or urea have been adopted for a reaction-rate instrument (LKB 8600) using conditions recommended by the Scandinavian Enzyme Committee, when applicable. The analytical results are directly evaluated for various groups of patients and also used in a mathematical "three-isoenzyme" model. These calculations did not improve the clinical value of the primarily obtained data. Thus, it was concluded that under certain precautions the results obtained in the presence of L-phenylalanine or urea should be used separately.