Abstract: A method for measuring the concentration or the activity of UTI quickly and easily at high sensitivity. A urine sample, a buffer solution, a trypsin solution and a substrate solution are mixed and the trypsin activity is then measured. Thus, the UTI concentration in the urine sample is determined. In this case, a substrate solution having only L-BAPNA is used as the substrate, and the surfactant is mixed in at least one selected from the buffer solution and the enzyme solution. The mixing ratio of the surfactant is about 1 wt. % in the entire enzyme reaction solution. Examples of the surfactant include polyoxyethylene (40) octylphenylether, polyoxyethylene (10) octylphenylether, 3-[(3-cholamido propyl)dimethylammonio]-propanesulfonic acid, 3-[(3-cholamido propyl)dimethylammonio]-2-hydroxypropanesulfonic acid, and polyoxyethylene sorbitan monolaurate. As shown in FIG. 1, the sensitivity improves when using L-BAPNA.

Abstract: This invention provides a method for measuring the concentration of urinary trypsin inhibitors which is excellent in precision and reproducibility, whose operation is simple, and in which a possibility of damaging a plastic cell is eliminated. The method for measuring the concentration of urinary trypsin inhibitors comprises mixing an urine sample, a protease solution containing trypsin, and a buffer solution, adding a substrate solution to the mixture to cause the enzyme reaction, and measuring the activity of the enzyme, wherein the buffer solution is prepared so that it contains at least 0.15 .mu.mol calcium per 1 .mu.g of the trypsin but no more than 100 .mu.